Ground Source - Heat Pumps Scotland

9 April 2022

Hybrid Heating System – What is a Hybrid Heat Pump and Should You Get One?

Hybrid heat pumps are an excellent way of improving the energy efficiency of your home without ripping out your whole heating system and replacing it with more efficient technology.

Hybrid systems combine renewable and traditional heating technology into a single system, which operates flexibly and brings the best of both worlds to your home.

Able to provide both space heating and hot water, they can be a great choice under the right circumstances.

So, is a hybrid heat pump system the right choice for you? Let’s find out.

What is a hybrid heating system?

First of all, let’s get a better understanding of exactly what a hybrid heating system is.

Fundamentally, a hybrid heating system is a system that makes use of two different heating technologies to provide hot water and heating to a property.

Normally, this will be a heat pump (often air source but could be ground source or water source) fitted alongside a fossil fuel boiler, running either on mains gas, oil or LPG.

Hybrid heating systems can be programmed to make use of electricity at times when this is cheaper, switching to the backup fossil fuel boiler at times of high heat demand or when the economics or carbon emission savings demand it.

Hybrid heat pumps can be a good choice for people who are looking to improve the energy efficiency of their home, but for which a standard heat pump is unsuitable.

Alternative heating systems

If you are considering installing a hybrid heat pump, it’s likely that you have an existing traditional heating system and are considering how far down the green route to go.

You could stick with fossil fuels, but that’s bad for the planet and does nothing to help mitigate climate change. It’s also likely to become more expensive as time goes on, with renewable energy technologies improving and becoming cheaper all the time.

The best approach to go for to minimise your carbon emissions and take advantage of the financial incentives that are available at the moment, is to install a stand-alone heat pump. However, stand-alone heat pumps are not always the best solution and in some circumstances may not be appropriate at all.

That’s where a combined hybrid approach could come in.

Let’s compare some of the alternatives.

Hybrid heat pump vs heat pump

When does it make sense to use a hybrid heat pump system as opposed to a stand-alone heat pump? There are several circumstances where this could be the smart choice.

You are on mains gas and gas prices are low

Modern gas boilers have become extremely efficient at providing heat and hot water with many condensing boilers having efficiencies upwards of 90%.

Such impressive efficiency figures, combined with the relatively low cost of mains gas, mean that many people who are lucky enough to be on the gas grid continue to enjoy relatively low-cost heating and hot water compared to people living in rural areas.

If you are on the gas grid, you might not save much money by installing a stand-alone heat pump. You would of course save in terms of your carbon emissions, but not many of us are in a position to put carbon emissions ahead of financial concerns – you can be as green and eco-friendly as you wish but if that means not being able to put food on the table, you have to refocus your priorities.

Rather than taking an all or nothing approach, installing a hybrid heat pump system could bring you the best of both worlds.

Some people set the heat pump part of their hybrid system to run only their space heating, typically making use of underfloor heating, which is very efficient in combination with a heat pump. The gas boiler can then handle hot water only, which could be better cost wise because the efficiency of heat pumps reduces slightly at higher output temperatures.

Your home has a very high heat demand

Simply put, the heat demand for a building is the amount of energy required to maintain it at a comfortable temperature.

The heat demand of a building can be estimated using multiplication factors, essentially rules of thumb, that apply to different categories of building.

Heat demand can also be estimated using records of the actual energy delivered to a property over the course of a year. This information should be available on your gas or electricity bill.

The less well insulated your building is, the higher its peak heat demand will be and therefore the larger the heat pump or boiler needs to be. This is for the obvious reason that a lot of heat will escape through the fabric of the building.

In addition to the heat required to maintain room temperature at a comfortable level, there is also a heat requirement for hot water.

If you know roughly how much water you use, it is straightforward to apply a standard conversion factor that will tell you the heat demand for hot water during a typical year.

If you are not on a water meter, you can estimate the amount of water you use by multiplying the number of people who live in the house by 142, which is the number of litres a typical person uses in the UK each day.

Multiply again by a factor of 0.0585 to determine the number of kilowatt-hours of energy required to heat your hot water (this assumes that water is supplied to your home at a temperature of 10°C and is heated to 60°C).

Of course, all these calculations can get quite involved and for this reason it is recommended that you consult a qualified professional to help with the design of your heating system.

Just know that if you live in a poorly insulated property or have a large family, your heat demand is likely to be high. This won’t always mean that a stand-alone heat pump is unsuitable and that a hybrid system is necessary, but you should take care to properly size your system and know what to expect in terms of cost upfront.

You are on a tight budget

Heat pumps are still more expensive to buy and install than traditional heating systems such as gas boilers. Everyone is hoping that this will change soon, but for now you’ll need deeper than average pockets to be able to afford one.

The Renewable Heat Incentive (RHI) helped to mitigate these larger upfront costs, but the incentive scheme has ended now. The Boiler Upgrade Scheme (BUS) is available in England and Wales but does not cover hybrid systems. In Scotland, there is no replacement for the Renewable Heat Incentive scheme as yet.

It is unclear whether even the zero VAT rating announced by Chancellor Rishi Sunak for energy-saving materials applies to hybrid systems. If government takes a similar view that under the Boiler Upgrade Scheme, then it’s unlikely that it will.

For these reasons, unless you are in the fortunate position of being able to put your green principles ahead of financial concerns, your wallet might thank you for sticking to traditional heating technologies for now.

Particularly if you are on the mains gas grid, which despite the recent price rises, continues to offer relatively good value for money when compared to more environmentally friendly alternatives.

Hybrid heat pump water heater vs gas

Another way to compare hybrid heat pumps is against the fossil fuel alternatives. For the sake of argument, let’s think about hybrid heat pumps compared with a traditional gas boiler that uses mains gas.

As we have touched on above, hybrids offer a middle path for those wanting to reduce their carbon footprint whilst allowing the flexibility of having a backup system for those days of the year when heat demand is particularly high.

If you have a very high heat demand and are not particularly concerned with reducing your carbon emissions, then you could probably stick with gas for now.

But, if you want to hedge against gas prices going up over time and can afford to install a hybrid heat pump now, this could offer the best of both worlds. Particularly if you have your system set up to use the heat pump when electricity is cheapest, with the gas boiler taking over at times when electricity is expensive.

Alternatively, you could run your space heating exclusively using low temperature radiators or underfloor heating in conjunction with the heat pump and heat your hot water solely using gas.

This is a nice setup because it plays to the strengths of each technology. The gas boiler can supply hot water quickly and efficiently, with the air source heat pump operating at relatively lower temperatures. This allows the heat pump to make use of the large heat transfer area available in underfloor heating to provide warmth at the lower temperatures it needs to operate at maximum efficiency.

Hybrid heat pump pros and cons

That was a lot of information to take in, let’s tease out the main pros and cons of hybrid heat pumps.

Advantages of hybrid heat pump systems

Able to cope with high heat demands.
Able to make use of cheaper electricity to provide warmth.
Reduce greenhouse gas emissions without sacrificing comfort.
Suitable for older houses or less well insulated properties.

Disadvantages of hybrid heat pump systems

Still contribute to global warming.
Do not qualify for financial incentives offered through the Boiler Upgrade Scheme (BUS)
More complex control requirements to achieve optimal efficiency due to the two-system approach.
More expensive to install than a fossil fuel-only boiler.

So, are hybrid heat pumps any good?

It depends on your specific circumstances, but they are a good option if you need the security of a backup boiler for very cold days.

With the right design and system controls they can be more efficient, cheaper to run and have lower carbon emissions than a fossil fuel alternative.

Summary

Hybrid heating systems are simply systems that make use of two or more heating technologies to provide a comfortable living temperature in your home and hot water for bathing and washing the dishes.

A hybrid heat pump can be air source, ground source or water source and typically operates in conjunction with a fossil fuel powered boiler.

Hybrid heat pumps offer the best of both worlds by allowing the heat pump to operate at maximum efficiency when the conditions are right.

This is when the temperature difference between outside and inside is lower, which means the heat pump does not have to work too hard at reduced efficiency. It can also be cheaper to run the heat pump when electricity prices are lower and the heat pump can heat the house more economically than the fossil fuel boiler.

One downside of hybrid systems is that they don’t necessarily qualify for the financial incentives offered by government to encourage the uptake of renewable heating technology. This is because they still have a fossil fuel component and therefore release carbon dioxide to the atmosphere, contributing to climate change.

Although hybrid systems still contribute to global warming, they are better than a fossil fuel-only approach and also have the benefit of a backup system for very cold days when a heat pump might not manage to provide sufficient heat at reasonable cost.

If you are interested in the possibility of installing a hybrid heat pump in your own home, please take a look around the rest of this website to learn more about heat pumps in general.

When you are ready to enter the market and find an installer, I’d recommend reading through our article about how to find a heat pump installer, which guides you through the process and includes advice on how to assess the credentials of a potential installer, including some questions to consider asking before you engage them in your project.

There is a directory of installers on our installers page, which you can use to find installers in your area who might be able to help you. These are provided as a starting point for your search and Heat Pumps Scotland does not endorse them in any way. Please conduct your own due diligence to ensure you employ a suitable installer.

7 April 2022

Alternative To Gas Boilers? Complete Comparison of Heat Pump vs Gas Boiler for UK

There has been a lot of hype in the news recently about whether heat pumps can be a good alternative to gas boilers.

The climate emergency now faced by humankind means we must dramatically reduce the amount of carbon that we are putting into the atmosphere. Governments all over the world are working towards achieving net zero carbon emissions, with the UK Government setting targets to deliver this by 2050 and the Scottish Government going even further to achieve net zero emissions of all greenhouse gases by 2045.

Heat pumps are very efficient at providing heat for our homes whilst at the same time reducing carbon emissions and we must roll out this technology widely across the country if we are to stand a chance of achieving our net zero goals.

The question on everyone’s lips is, “How do heat pumps compare to gas boilers, and can heat pumps be a viable alternative to gas boilers?”

The short answer is that heat pumps are indeed a viable alternative to gas boilers, but let’s look at this in a bit more detail.

First, a reminder of what a heat pump is.

What is a heat pump?

The simplest analogy for a heat pump is the fridge in your kitchen. The fridge removes heat from inside the cooling compartment and dumps that heat into the kitchen via the coils on the back of the appliance.

A heat pump works in the same way, but instead of removing heat from inside of the fridge, it takes the heat from the outside environment (either from the air or, in the case of a ground source heat pump, from the ground). It then concentrates the heat it has collected using a compressor before releasing it inside the house.

It’s a simple technology that people have been using for years, but in Scotland we have been slow to apply it to heating our homes.

Practical considerations

We all have a lot on our plate, with family, work and other commitments vying for our time. We want our heating systems to “just work”, providing warmth without any fuss, so we can get on with our busy lives.

There has been good reason in the past for people to heat their homes using fossil fuels, not least the low running costs of a gas boiler using mains gas. The economics and convenience of such systems have resulted in 80% of domestic properties in the UK being heated with mains gas.

If you are considering a move towards more environmentally friendly alternatives, you are probably wondering whether a heat pump can deliver the same convenience, warmth and affordability as a gas boiler.

Let’s look at some of the most common questions people have about heat pumps.

Can a heat pump heat a whole house?

The short answer is yes, a heat pump can heat a whole house.

Heat pump systems must be carefully designed and consider the specifics of the house they will be heating. For example:

Is the house well insulated?
What is the preferred temperature of the rooms being heated?
What is the outside temperature?
How much outdoor space is available?

All these things will influence the size of the heat pump required, and whether an air source, ground source or water source system would best suit.

If there is plenty of space available to bury the collector pipe, perhaps ground source heating is worth looking into, or if there is a suitable body of water close by, a water source might offer the best efficiency.

In any case, a properly designed heat pump system will have no trouble heating a whole house.

Is it cheaper to run a heat pump all the time?

Some people like to be able to turn their heating on and off quickly, for example so they can open the windows and let in all that lovely fresh air without wasting money heating the outside of their property.

A common question about heat pumps is whether they need to run continuously to be effective. If that was the case, it would put off the fresh air fiends out there because they would have visions of living in a hermetically sealed box with no access to fresh air.

In general, it is not cheaper to run your heat pump all the time. Most people find that setting their heat pump to a lower temperature overnight saves them money on running costs. Likewise, not running your heat pump while you are out at work, or away for the weekend will reduce running costs, too.

Something to consider, particularly if your property is relatively modern and airtight, is a heat recovery and ventilation system. The system will allow your home to receive fresh air without having to open your windows. Instead, fresh air is blown into your house to provide ventilation and the incoming air is warmed using exhaust air, which saves on heating bills without compromising air quality. Perfect for the fresh air fiends out there.

At what temperature do heat pumps become ineffective?

The short answer to this question is typically at temperatures below those experienced in Scotland (heat pumps can operate at temperatures as low as -25°C).

This is perhaps the wrong question to be asking though. If you have a heat pump that can operate in outdoor temperatures as low as -25°C, you’ll be fine pretty much anywhere in the UK on any day of the year.

Perhaps what you should be asking though is whether the particular model of heat pump that you will be using is effective at those very low temperatures.

Not all heat pumps can operate in such cold environments, so it’s important to check that yours will if you need it to.

Something else to think about is the efficiency of the heat pump system, which isn’t only related to the outside temperature, but the difference between the indoor and outdoor temperatures. If you are used to keeping your home at 35°C to be comfortable, you might find your heat pump never quite gets you there.

The wider the gap between the outside temperature and the desired indoor temperature, the harder your heat pump will have to work to maintain that indoor temperature. The harder your heat pump has to work, the less efficient it will be.

This is why low temperature underfloor heating is a good match for a heat pump – the large surface area allows for sufficient heat transfer without the need for high temperature radiators. This in turn allows the difference between the inside and outside temperatures to be kept small, resulting in a more efficient heat pump system.

Heat pump efficiency

I just touched on the issue of efficiency, and it is worth sticking with this topic for a moment.

How is heat pump efficiency measured?

The main statistic that is used to measure the efficiency of a heat pump is the Coefficient of Performance (COP).

What is COP?

COP, simply put, is the ratio of the amount of electrical energy required to operate a heat pump to the amount of heat energy it produces.

So, for a heat pump that produces 4 units of heat energy for each unit of electrical energy consumed, the COP would be 4.

What is a good COP for a heat pump?

A COP of 4 is excellent and an expected range for heat pumps in the UK would be between 2.5 and 3.5.

Heat pump carbon savings

The top end of the COP range equates to an efficiency of 350% for a heat pump, which is a lot better than even the most efficient, modern condensing boiler, which can only manage 90% or so efficiency.

There is really no comparison. Plus, when you take into account the fact that the electricity grid is becoming greener all the time, with renewable energy becoming an ever larger proportion of the electricity generation mix, the carbon savings of using a heat pump compared to a gas boiler are huge.

If you can generate your own electricity using renewable solar PV, wind turbines or something else, then that brings even greater carbon savings – possibly even going beyond net zero.

Financial considerations

In the previous section, I explained how a heat pump can provide the same convenience and comfort as a gas boiler. The all-important issue of cost is next under the microscope, and this can be broken down into installation and running costs.

Zero VAT for heat pumps

The Chancellor’s announcement that rate of VAT payable for heat pumps would be zero for the next five years is surely a welcome fillip to the sector, but heat pumps are still a relatively expensive option in terms of up-front installation costs compared to more traditional options such as the gas boiler.

Boiler Upgrade Scheme (BUS scheme)

The Boiler Upgrade Scheme only applies to England and Wales. It aims to encourage the use of heat pumps and biomass boilers for space and water heating in certain properties.

Hopefully a similar scheme will be announced for Scotland and Northern Ireland that can replace the Renewable Heat Incentive (RHI), which ended on 31 March 2022 after a one year extension to its original lifetime.

Heat pump installation costs

Installation costs of a heat pump will vary according to the type and size of heat pump required. For a 2-3 bedroom house, they typically range from £8,000 for a medium-sized air source heat pump, to £20,000-£30,000 for a ground source heat pump.

The reason for the large difference in price is largely due to the substantial groundworks required for a ground source heat pump. The ground collector either has to be buried in trenches, or installed in a borehole, which requires specialist borehole drilling machinery, which is also expensive.

Octopus Energy are spearheading a move to bring down the costs of installation of heat pumps by optimising the installation process. They are also working with heat pump manufacturers to bring down the cost of the units themselves. Fingers crossed they mange to do this and, in the process, make heat pumps available to a wider market.

Heat pump running costs

The running costs of heat pumps depend mainly on the cost of electricity because they only need a service once a year and this is not particularly expensive (approximately £200 plus parts).

With the energy crisis grabbing headlines recently, you can’t fail to have noticed that the cost of electricity has gone up, a lot.

But so has the cost of gas, which means the scales haven’t necessarily been tipped in favour of fossil fuels.

Let’s take a look at the cost of running a heat pump for the 2-3 bedroom property we used as an example above. Before the price rises, the cost of heating a home like this would come in at just under £1,000 per year, which is around £200 cheaper than an equivalent gas boiler driven system.

As a result of the price cap rises, electricity has gone up around 72% on average, but gas has risen even more (by around 84% on average), which means that the savings likely to result from using a heat pump compared with a gas boiler are even greater.

But I’ve heard that heat pumps are worse than gas boilers

Let’s bust some heat pump myths!

If you’ve spent time researching heat pumps on the internet, you will have come across stories of people paying extortionate amounts for their electricity since installing a heat pump. Or perhaps even worse stories of cold homes and unreliable equipment.

What many of these stories have in common is that the heat pumps in question have been incorrectly designed and/or installed.

Normally, those complaining online of an unsatisfactory experience with their heat pump are met with responses from lots of satisfied heat pump customers offering advice and sharing their more positive experiences.

One such positive experience was shared online at the Home Farm website, as follows.

“We have a 4 bedroom house and had an ASHP installed in September 2021. Our heat pump is a 12kW Vaillant. The cost of heating and hot water from 7 November – 7 December 2021 was £144. The heating is on from 06:00 hours to 20:30 with a 2 hour break in the middle. The hot water is set on for a 12 hour period. We live in a frost hollow in eastern Scotland and have gone through two storms in the last two weeks and overnight temperatures hovering at around zero for the last fortnight. Our home is timber-framed and reasonably well insulated but the bedrooms upstairs have 30 years old velux windows which are not particularly well insulated. We only upsized the downstairs radiators. Despite all of this we find we are warm and cosy.”

This was in response to someone posting a comment about their air source heating costing £6,000 per year to run. Such high running costs are not the typical experience but give credence to the critics and naysayers who wrongly spread rumours about heat pumps not being capable of heating houses efficiently in the UK.

The unfortunate truth is that there are companies out there installing heat pumps who shouldn’t be. Buyer beware is good advice and if you can, it’s a good idea to educate yourself on system design basics so you know what questions to ask.

Failing that, make sure you get good recommendations and always follow up on references before going with an installer.

Summary

Heat pumps are a good alternative to gas boilers for your domestic hot water and space heating needs.

Heat pumps are a very effective way to reduce your carbon footprint and save money on your heating bills in the long run, provided they are correctly designed and installed.

Are heat pumps worth the money?

Yes. They cost more up front than gas boilers, but the installation costs are mitigated by their zero VAT rating and the availability (in England and Wales) of financial assistance in the guise of the Boiler Upgrade Scheme (BUS).

Heat pumps are cheaper to run across time thanks to their superior efficiency.

Are heat pumps a good alternative to gas boilers? The Key points

Heat pumps are a good alternative to gas boilers.
A heat pump can heat a whole house.
It is not cheaper to run a heat pump all the time.
Heat pumps are effective down to temperatures as low as -25°C.
Heat pumps save carbon emissions vs gas boilers.
Installation costs of heat pumps are larger than for gas boilers but financial incentives are available to help with the costs.
Heat pump running costs are normally lower than gas boilers, provided they are properly designed and installed.

16 March 2022

Demand For Ground Source Heat Pump Grants In 2022 Grows

Ground Source Heat Pump Grants needed in 2022.

Ground source heat pump grants are back on the agenda in 2022 as the UK government comes under increasing pressure to make money available for the installation of heat pumps.

A total of 33 civil society groups have written to Boris Johnson, the UK Prime Minister, and Rishi Sunak, Chancellor of the Exchequer, calling for grants to be awarded to all households for the installation of additional insulation and heat pumps.

Energy Crisis

Signatories to the letter include Greenpeace, friends of the Earth and save the children. They all point out that the cost of living crisis, which has been coming down the tracks for many months, but has gone into overdrive with the recent war in Ukraine, will disproportionately impact vulnerable families.

Many households in the UK are already having to make the difficult choice between heating their homes and feeding their children. But spiralling energy costs are making the situation much worse, with prices set to rise at the end of the month and again in October as the energy price Increases once more.

Rising fuel bills are further compounded by increases in the cost of food and other goods right across the board, which all require energy to produce and transport to consumers.

Climate Targets and Renewable Energy

The ambitious targets to achieve net zero carbon emissions by 2050, which the Conservative party committed to under to Theresa May, are vital if the UK is to be seen to be pulling its weight in tackling climate change.

But progress has slowed and the disappearance of the renewable heat incentive at the end of March is expected to result in a drop off of new installations of renewable heating.

Added to that is the impact of the war in Ukraine, which has raised concerns about security of oil supply and sent prices skyrocketing. Boris Johnson has this week travelled to Saudi Arabia to speak with the Crown Prince about these issues and the possibility of the UK securing additional supplies from the Saudis. This is despite criticisms levelled at the Prime Minister by many people who think he should not be entering into such discussions given recent allegations of human rights abuses in Saudi Arabia.

Rather than seeking to obtain oil from countries other than Russia, many think that this is a golden opportunity to increase incentives for people considering the installation of renewable energy such as heat pumps. The government is already committed to this, they just need to follow through with the money.

Ground Source Heat Pump Grants 2022

Rishi Sunak announced a £9 billion package to help tackle the energy bills crisis and sources in the administration have indicated that this must be kept under review because further help could be required in future.

These are large sums of money being made available, but they do nothing to move us nearer to reaching the climate targets that the Tories signed up to under the previous administration.

Wouldn’t it be better to have a new push towards boosting the installation of heat pumps, with new subsidies aimed at replacing fossil fuel burning boilers with clean, green, eco-friendly heat pumps?

If we can give the heat pump industry a helping hand with grants and subsidies, the expectation is that the price of this technology will come down. With the increase in demand driven by incentive schemes, British companies can feel confident in investing in more manufacturing capacity, with some saying that the price could halve as a result.

There is also massive investment required to train up a new generation of heat pump engineers to install all these heat pumps. Octopus energy is investing £10 million to create a huge training facility for heat pump technicians, which will go some way to meeting this demand. With government help, this can be replicated across the country and the UK could be a world leader in heat pump technology.

The Case For Heat Pumps

Given the twin drivers of improving energy security and moving away from fossil fuels towards more climate friendly ways of heating our homes, surely the government can find its way to make money available for additional ground source heat pump grants in 2022?

The government has previously stated that it wants to install 600,000 heat pumps in UK homes by 2028. This is a massive target and will need support from incentive schemes and training programs to ensure that people can afford to install these systems and that we have enough heat pump engineers to carry out the work.

If we don’t, we will face runaway climate change, which will wreak havoc on our society for generations to come. Let’s see some action before it’s too late.

15 March 2022

Ground Source Heat Pump Borehole Cost Revealed

Ground source heat pumps (GSHP) make use of the heat available under the ground to heat your home. They offer a number of advantages over air source heat pumps but tend to be more expensive due to the initial ground source heat pump borehole cost, which can be more expensive than the alternative, horizontal trenches.

What is a heat pump?

Heat pumps move heat energy from one place to another, in the case of a ground source heat pump this means moving the heat that is present under the ground into your home, where it is used to raise the inside air temperature to a comfortable level and can also be used to heat your domestic hot water.

But how do they work exactly?

How do heat pumps work?

You can think of a heat pump as a refrigerator running in reverse. Instead of taking the heat from the inside of your fridge compartment and moving it to the back grill of the fridge, where it is emitted to the air in your kitchen, a heat pump takes the heat present outside your home and transfers it into the building.

The heat is usually distributed around the building using either underfloor heating and low-temperature radiators. Underfloor heating is a great way to achieve this distribution of heat, because heat pumps work most effectively at low temperatures, which requires a larger surface area for the transfer to take place. Placing pipework underneath your entire floor area can provide a huge surface area and also has the pleasant side-effect of keeping your feet nice and cosy.

The transfer of heat from outside to inside is achieved using the refrigeration cycle, which makes use of refrigerant fluid to absorb the heat, before concentrating it using a compressor. Finally it is passed through a condenser, across which air may be blown, which has the effect of heating the air to the desired temperature.

This warmed air is then circulated around the home, sometimes with the use of ducts, but it may also just be blown into living space as is the case in a ductless system.

What is a ground source heat pump?

The principles defining the operation of all heat pumps are fundamentally the same, as outlined above in the previous section. There are a few main types of heat pump, including air source heat pumps, water source heat pumps and ground source heat pumps. In addition to these main types, you can also get exhaust air heat pumps, which as you might imagine extract their heat from the exhaust air from a building that has a mechanical ventilation system installed.

In this article, we are focusing on ground source heat pumps. But where does the heat come from for a ground source heat pump?

The facile answer to this question is “from the ground”, but the real question is how does the heat get there in the first place?

It is possible to drill deep enough to make use of heat from the Earth’s molten core. If you’ve ever been down a deep mine, you will have noticed that the deeper you go the warmer it gets. That’s not due to the machinery in operation down there, or even all the hard-working bodies. It’s actually because you are getting closer to the Earth’s molten core.

The temperature gradient as you travel down through the Earth’s crust means that for every kilometre you travel vertically downwards, the temperature increases by about 25°C. So, believe me can get pretty hot down the mine – plenty hot enough to power a ground source heat pump.

But making use of geothermal energy from the Earth’s core is the exception rather than the rule when it comes to ground source heat pumps.

Most of the heat energy used by has its origin in the sun. As the sun shines down on the Earth’s surface, heat is transferred and absorbed by the ground. Most ground source heat pumps tend to be relatively shallow in construction and therefore source most of their heat from the shallow ground but is warmed by the sun.

The average temperature at moderate depth below ground level in Scotland is approximately 10°C, and this temperature remains relatively stable all year round. And this is one of the key advantages of a ground source heat pump.

Whereas air source heat pumps tend to have to work harder during the cold winter months because there is less heat available in the cooler air, ground source heat pumps have the advantage of obtaining their heat from the more stable conditions underground.

This allows a ground source heat pumps to operate more efficiently, particularly during the winter. The big benefit of this is that you use less electricity, which not only is better for the planet, but also save you money. Something that is very welcome indeed given the current energy crisis sending electricity prices soaring.

How much land do you need for a ground source heat pump?

Ground source heat pumps fall into two broad categories, namely those that bury the pipework in long shallow trenches and those that install the pipework in vertical boreholes.

How much land you need depends on which option you select, as well as the size of the ground loop required to provide heat to your system.

The length of pipe needed for a ground loop can be as much as 400m, but a typical GSHP system will likely require between 600 and 1200m2 of land to accommodate a horizontal ground loop, or a much smaller footprint for a vertical borehole (typical diameter approximately 150mm).

Ground loop in shallow trench

There are obvious benefits to using a shallow trench. Installing the ground loop in this way does not require specialist drilling techniques, which can make things cheaper.

However, digging a series of large trenches requires a lot of space and will make a mess of your back garden.

If you install a series of trenches in your back garden or, if you’re lucky enough to have one, your field, you will have diggers driving all over it, churning up the ground. By the time they’ve finished, the mess that’s been made could take over a year to recover from.

Cost of digging the trench

For a typical horizontal ground source heat pump, with the ground loop installed in a trench, you can expect to pay the digger driver up to 5 pounds per square metre of trench. This assumes you have suitable ground conditions, which can be easily dug through. A JCB can dig through some types of bedrock, but if you encounter hard granite or something similar near the surface, this can slow things down considerably and cost you more.

Boreholes for ground source heat pumps (GSHP)

Boreholes have the advantage of not making such a mess of your field and require a lot smaller footprint because they are drilled vertically downwards.

Boreholes can also be installed through concrete and tarmac surfaces, so are a much better choice if you want to install the collector under your company car park or your home driveway.

Ground source heat pump borehole cost

The exact cost of drilling boreholes for a ground source heat pump depends partly on the underlying geology of your site.

If there is a good thickness of drift overlying bedrock your site, which comprises mainly sand and gravel, the drilling will be comparatively easy going. However, if there is little or no drift and your drilling company has to drill through hard bedrock, this will take a lot longer and be more expensive.

The finished depth of the borehole obviously plays a part in determining the overall cost is drilling deeper will be more expensive.

Typical prices for boreholes range widely for the reasons given above. However, you could expect to pay £40 per metre, and I have seen costs as high as £100 per metre for drilling through tricky geological conditions.

Some of the other things that can affect the final cost of the borehole include obvious things like the diameter, and less obvious things such as striking water, which could be at pressure in certain areas and require special handling. This could include the use of grout to seal the borehole and bentonite clay to prevent the water crossing over into other strata and potentially rising to the surface where it could cause localised flooding problems.

Types of borehole

There are two main types of ground source heat pump loop that relate to boreholes. These are closed-loop systems and open-loop systems.

Closed loop

As the name suggests, a closed-loop system pumps fluid through a pipe which extends down the borehole, where it collects heat from the ground. The same fluid continues its journey back up the borehole, where it is passed through the heat pump to utilise the heat captured.

Open loop

Open-loop systems on the other hand will typically abstract groundwater from deep down in a borehole, which is then passed through a heat exchanger and heat pump to extract the heat.

The same water, now cooler after having had some of its heat removed, would be discharged, often down a separate borehole, into the aquifer from which it came. Hence the term open-loop.

Are boreholes expensive?

Whether you think boreholes are expensive for use with ground source heat pumps depends on your perspective and circumstances.

If you are on a tight site, with little space to dig horizontal trenches, boreholes might be your only option.

Similarly, if your site is covered with concrete, or maybe a nice smart car park surfaced with tarmac and lovely painted lines, it would prove costly to dig that all up and reinstated after digging extensive horizontal ground loop trenches for your ground source heat pump.

In such circumstances it would make far more sense to drill a borehole.

So, although drilling boreholes can be expensive, they are certainly an option worth considering, especially if you don’t have much space or the space you do have is taken up with high-value uses that would be costly to reinstate.

Types of borehole drilling rig

Drilling geothermal well for a residential geothermal heat pump. Workers on Drilling Rig. A worker prepares to join two pieces of drill pipe on a drilling rig.

It’s worth mentioning that there are different types of borehole drilling rigs in use and the type of rig can affect the cost and speed of drilling. You might find you need to use a specific type of drilling rig if the geological conditions underneath your site require it, or if you are in a hurry you might choose a faster drilling method.

Here are some of the options available to you.

Percussion

The standard percussion drilling rig is a piece of kit you will probably have seen on many building sites.

It is usually operated by a two-man team and comprises a steel bit suspended by a cable. The steel bit is hoisted on the end of the cable and repeatedly dropped down the borehole, thereby pulverising the rock and scooping the spoil backup to the surface.

There are many different tools available we can be fitted to the end of the cable for different ground conditions. These include the shell type, which is used for drilling in soft ground like sand and gravel, and the cross chisel, which is used to break up boulders and from drilling through hard rock.

The different tools are normally fitted to a sinker bar, which adds weight and power to allow drilling to proceed more quickly.

Rotary

Rotary drilling is much faster than percussion drilling and is ideally suited for drilling deep boreholes.

The cutting head is fitted to the end of the shaft and rotates at speeds of up to 120 rpm. The spoil is removed from the borehole using either high-pressure air or drilling fluid. The air or drilling fluid also serves the purpose of cooling the drill bit as it bores through the rock.

Down the hole hammer

Down the hole hammer is basically a pneumatic drill attached to the end of the drill string. As you can imagine, this helps to make light work of hard rock and combines the fast hammer action of the pneumatic drill with rotary drilling action.

This is a highly effective form of drilling and is one of the fastest ways to drill through hard rock.

How deep is a borehole for a ground source heat pump?

The typical depth of borehole for use with a ground source heat pump system is between 60 and 200 m. The diameter is normally around 150 mm and multiple boreholes can be combined into arrays, which increase the amount of heat that can be made available for the system.

How much do boreholes cost?

The minimum cost for a borehole to be used with a ground source heat pump might be less than £10,000, but costs can rise much higher than that – easily up to £30,000 or more.

As stated above, there are many variables that determine how much you pay for a borehole, including depth, diameter, underlying geological conditions, whether water is likely to be encountered et cetera.

It pays to get good advice in advance when considering your options.

How much does it cost to fit a ground source heat pump?

The overall cost for fitting a ground source heat pump depends on the capacity required and the type of ground works employed.

According to the Energy Saving Trust, the cost of installing a ground source heat pump for a two-bedroom property is around £16,000 exclusive of the ground work cost. Ground works for this type of property could be approximately £3000 for a horizontal trench dug ground loop, or £6000 for a borehole ground loop.

The cost of installing a similar system in a six bedroom property is estimated to be around £32,000 not including the ground works. Horizontal ground works for this type of system are estimated to be in the region of £8000, with vertical ground works estimated at £20,000.

Is ground source heating cost effective?

Despite the high installation costs of ground source heating, in the right circumstances it can be a very cost-effective form of heating.

Properly designed, operated and maintained, running costs can be lower than almost any other solution.

Such low running costs can be achieved as a result of the stable and relatively warm underground temperatures accessed using ground source heat pumps. This allows the heat pump to operate efficiently throughout the year, even when outside air temperatures are at their lowest, which is when air source heat pumps can run less efficiently.

When installed in a well insulated building and where ground conditions mean that the installation of the ground loop isn’t too expensive, ground source heating can be very cost-effective.

Summary

Ground source heat pumps can be a very energy efficient and cost-effective way to heat your property.

Provided you have the right ground conditions and a well-insulated house, ground source heating systems have some of the lowest running costs around.

If you are limited for space or don’t want to dig up large areas of your plot to accommodate a horizontal ground loop, a ground source heat pump borehole is worth considering. The initial installation cost, although high, can be worth it in the long run.

If you’re interested in finding out more, take a look at some of our other articles about heat pump options. Once you’re ready, why not take a look at our article on how to find a heat pump installer, which provides information on what you can expect and gives you some pointers on the right questions to ask.

11 March 2022

Best heat pump thermostat settings for Scotland’s climate

A question we are often asked here at Heat Pumps Scotland is what is the best heat pump thermostat settings to use for the Scottish climate?

What most people seem to try is randomly adjusting their thermostat in a process of trial and error until they happen upon the best setting for their home. The problem with doing this however is that you can waste a lot of time and energy searching for the right place on the dial. Also, unless you keep a close eye on the efficiency of your heat pump system whilst doing this, all you’re really doing is yo-yoing around some notion of your ideal temperature and probably ending up with a somewhat uncomfortable home environment with little or no gain in efficiency and cost.

What is the most efficient setting for a heat pump?

What you should try to do when finding the best heat pump thermostat setting is to get the perfect balance between comfort and energy efficiency, which is different for everyone. A well-off person who likes a very warm home might favour a setting which keeps their home lovely and warm but is quite expensive to run. However, a more environmentally conscious person, or someone who is on a tight budget, might be willing to turn the thermostat right down in order to save the planet and or their wallet, especially if they don’t mind the cold, or perhaps even prefer their home to be on the cool side.

A good rule of thumb is to keep your heat pump thermostat set to between 20 and 25°C throughout the winter.

What temperature should I set my heat pump thermostat to?

Although in Scotland most people will use their heat pump for heating pretty much all the time, it is possible to use it for cooling your home during the summer. If you have a system that allows you to do this, you will need to adjust your thermostat to the optimal setting for winter or summer depending on the season.

Best temperature to set a heat pump to in winter

The best temperature to set your heat pump to in winter is around 20°C. Turning the temperature down a bit during the winter months can save you some decent money here in Scotland. The only exception to this would be if you have an auxiliary heat system that kicks in during very cold spells. If you have a backup gas boiler or oil fired boiler, which takes over when temperatures are at their coldest and when your heat pump would struggle, it might make perfect economic sense to keep the temperature setting for your heat pump higher and rely on this auxiliary heating system to fire up when needed.

One thing I would recommend though is turning the stat down while you sleep at night. The same could be true if you’re not actually in the home, for example during the hours you are out at work. There is little point hitting an entire house when you’re tucked up safe and cosy in your bedroom or else not even there at all.

Best temperature to set your heat pump during the summer

Let’s face it, in Scotland you’re very unlikely to need your heat pump to provide cooling, even during the hottest summer days. But if you have such a unit installed and find occasion to use it, it would be advisable not to set it any lower than 25°C.

Again, think about how you could make best use of the system, perhaps by turning it off at night and when you are out.

What can affect your heat pump setting?

Your home is likely to be fairly unique in terms of his heating and cooling characteristics. Even houses built right next door to each other can have quite stark differences in the level of insulation they have, how much ventilation is available, not to mention the preferences of the occupants.

For example, I know someone who lives at the top of the hill in a small village. They never had any problems with a lack of ventilation because the breeze at the top of the hill provides plenty of natural cooling. It also has the benefit of minimising the nuisance caused by those pesky Scottish midges!

Just a few hundred metres down the hill however, my other friend has a house which is quite sheltered and is very little breeze resulting in quite sticky hot temperatures in his home during very hot days. We also have a hard time of things on summer evenings when the midges come out and attack everyone who is in the garden, which has ruined a few good barbecues.

Outdoor temperature

If you can get away with setting your heat pump to a similar temperature to that outside, you’ll find it will run very efficiently and not consume a lot of energy. As temperatures plunge during the winter time, heat pump efficiency also goes down.

A large difference between the outside and inside temperatures will make your heat pump work harder and consume more electrical energy. This in turn will cost you more money, not to mention the fact it is bad for the environment.

Humidity level

In these mild Scottish climes, humidity can tend to creep up to uncomfortable levels. I found this to be particularly true in forested areas, where moisture from the evapotranspiration of trees is compounded by the shelter afforded from the breeze by woodland vegetation. This can make summer days where the Mercury hasn’t risen all that far feel sticky and oppressive.

Most people find that humidity levels between 30 and 60% feel comfortable. It’s best to keep your homes humidity levels somewhere in the middle of that range.

During the winter months, when condensation can become a problem indoors, it’s advisable to keep humidity levels towards the lower end of the range mentioned above. The dryer the atmosphere, the less chance of condensation.

If condensation is allowed to form through a combination of excessive humidity and humid air coming into contact with cold surfaces, this can become a real concern both for the integrity of your building and for the health of its occupants. Condensation can cause the buildup of mould, which poses a threat to human health.

One way to deal with this is to open the windows and allow the human air to escape, but heating your home with the windows open, even just on vent, will make your heating system much less efficient and expensive to run.

Sensible settings for your heat pump while you’re out

There is no need to have your heat pump working hard while you’re not in the building. So, best practice is to turn the temperature on the thermostat down during the wintertime if you’re not in.

Likewise, if you are using your heat pump for cooling, during the summer allow the thermostat to be notched up a little while you are not at home.

These practices will allow the heat pump to not work as hard when it doesn’t need to, which will save you money and energy.

Run your heat pump on a lower power setting overnight

When you go to sleep at night, it makes sense to turn the temperature down on your heat pump during the winter, say to 20°C. During the summer, if using it for cooling, allow the temperature to creep up a little, say to 25°C.

When you’re asleep, your metabolism slows down and your body naturally generates less heat. This means that you can get away with it being warmer during the summer without breaking into a sweat. And during the winter, even though your body is naturally generating less heat while you sleep, it’s likely you’ve got your thermals on and are wrapped up in a nice thick duvet.

So take advantage of these times when you don’t actually need your heat pump to be running flat-out, and let it take a break, conserving energy and costing you less.

How to maximise your heat pump’s efficiency

We’ve covered basic principles of how to make sure your heat pump is running as efficiently as possible. Let’s look at some specific steps that you can take to maximise that efficiency.

Regular heat pump maintenance

This is often overlooked by heat pump consumers, but it is incredibly important to keep your heat pump well-maintained. Even simply cleaning the important components regularly, such as the fan blades, can help to prevent the efficiency of your heat pump reducing over time. It can also have the added benefit of reducing the noise from the fan on your unit.

Other things that will be taken care of through proper maintenance include regassing the refrigerant so that it is always that the correct pressure and there is sufficient refrigerant in the system. Also, cleaning air filters regularly will obviously ease the flow of air through the unit, which for obvious reasons will help efficiency. Removal of a buildup of ice, which can often happen during the winter, will also improve the efficiency of an outdoor heat pump unit.

Improving Insulation and making sure your building is airtight

This is the elephant in the room and attention needs to be drawn to it. If your house is poorly insulated, you might find your heat pump struggling to keep your house warm. Likewise if you have cracks allowing drafts to blow through your house this will cause your heat pump difficulty in maintaining a comfortable temperature inside.

The only way to fix this is to retrofit proper Insulation, either rock wool, insulation board or whatever suits your circumstances. A tube of mastic can also work wonders for sealing up any cracks through which drafts are blowing, especially important in windy areas of Scotland such as on the coasts and particularly the islands.

Use of curtains

It can seem a little obvious and perhaps low-tech, but closing the curtains to prevent sunlight streaming in can really help to keep your house cool, particularly if the windows are south facing.

Likewise, curtains closed at night during the winter can help to minimise drafts and improve heat retention around windows in your home. I’ve also seen curtains drawn across front doors and even interior doors, which also seem remarkably effective in keeping drafts out and improving heat retention in homes.

Summary of best heat pump thermostat settings

So in summary, the best way to ensure your heat pump is running as efficiently as possible is to keep the temperature on your thermostat as close as possible to the temperature outside. This means your heat pump doesn’t have to work hard to maintain a large temperature difference.

Adding the useful tips provided above to ensure heat loss is minimised through the use of curtains, good Insulation and proper maintenance will ensure your heat pump operates as efficiently as possible for many years to come.

It’s all about finding the right balance for you – turning your heat pump down just a few degrees can make a huge difference to efficiency, which is great provided it doesn’t cause you too much discomfort. This decision is very personal and varies from household to household.

Whatever you do, though, make sure you get professional advice to ensure your heat pump system is appropriately designed and fitted so that it performs well for your particular preferences, type of home and how you live your life.

10 March 2022

Grant Heat Pumps – Have You Heard of Them?

Grant heat pumps have been manufactured under the Grant UK brand, which has been manufacturing high quality, easy to install, and low maintenance heating products for off-grid homes for over 40 years now and the company has always enjoyed high popularity in its niche thanks to the exceptional mix of value, reliability and performance of its products.

Formerly, the company’s oil-fired boilers used to be its most popular and standout product. In recent times, however, Grant has heavily invested in developing renewable heat technologies and it is right there in the forefront when it comes to delivering high-performance, sustainable products for off-grid homes.

Grant Air Source Heat Pumps: Aerona³ R32

Grant Aerona³ R32 line of air-to-water heat pumps are among the most efficient and popular air source heat pumps available at current. These MCS approved products use the latent heat in the outside air to heat radiators and under floor heating and to provide hot water.

All four models in the range can work highly efficiently in sub-zero temperatures and are great alternatives to traditional heating systems (gas, oil or electric) that are inefficient, come with high running costs and are not up to scratch at all. So, if you’re planning a switch from your old boiler to a sustainable and renewable heating system for your home, the Grant Aerona³ R32 ‘Homeowner’ air-to-water heat pump models come off as great options.

Grant Aerona³ R32 Heat Pumps for Domestic Consumers

The Aerona³ R32 models are designed for domestic consumers and are available in four single phase standalone units of different sizes, with outputs of 6kW, 10kW, 13kW and 17kW. So, no matter the size of your property, there is a unit to fit your requirements.

And all four units in the range boast of great CoP (4.5 – 5.4 on average in all climate conditions) and the range as a whole enjoys an outstanding ERP rating of A+++, meaning that installing one of these units will significantly reduce your heating costs and your carbon footprint. One also will be happy to know that all the units are low-maintenance, easy-to-install and come with extremely low noise levels.

All the units in the Aerona³ R32 range use R32 refrigerant (hence the name of the range) and are fitted with in-built weather compensation. The heat pumps extract the heat from the outside air and transfer the same to a water-based heating system and they will work efficiently at temperatures as low as -20°C. The use of R32 refrigerant is also a great choice as it comes with a significantly lower carbon footprint potential compared to typical air source heat pump refrigerants.

Grant Heat Pump Prices

All heat pumps, including the Grant models, come with relatively high upfront installation costs. You can expect to pay anything between £6,000 and £14,000 for the installation. The cost will depend on three factors: your choice of model, the labour charge for the company that carries out the installation, and whether or not you’ll need necessary reconfigurations (installing underfloor heating if you don’t already have it and/or replacing your existing radiators with larger ones).

However, the initial cost of installation, especially for retrofit projects (installation costs come down considerably for new properties), can be offset through Domestic RHI payments and green finance schemes, given the installation of the pump meets certain designated criteria (more on that below).

As for the price of the Grant Aerona³ R32 models, you’ll need to pay £2,700, £4,020, £4,620 and £5,394 (including VAT) for 6kW, 10kW, 13kW and 17kW output units respectively.

Are Grant Heat Pumps Noisy?

Not only are Grant heat pump Aerona³ R32 models not noisy, they are actually favoured by consumers for their reduced level of noise and whisper-quiet operation.

This is especially important for people living in areas where there are noise restrictions in place. In fact, the Aerona³ 13kW and 17kW models are Quiet Mark awarded (Quiet Mark being an international technology resource platform that assesses and certifies the quietest solutions vis-à-vis any particular technology) and that in itself speaks volumes about the low operating sound levels of the units.

Also, according to reviews posted by users, all Grant heat pump models are among the quietest within their category.

Grant Heat Pump Reviews

At the time of writing this article, Grant UK has a 4.4/5 rating at Trustpilot based on over 2,000 reviews – the majority of them coming from current users of Grant domestic air-to-water heat pumps. As many as 81% of reviewers have labelled the brand as ‘Excellent.’

As for individual reviews, most people have expressed their appreciation for the quietness of the units, their convenience regarding maintenance and installation, and for the comfort levels provided by the models. We must also point out that all reviews found at Grant UK official website are sourced from Trustpilot itself.

Eco Experts, an independent online eco-friendly solutions guide for UK homeowners, has also named the Grant Aerona³ R32 17kW model as the ‘Best Overall’ air source heat pump in their Best Heat Pumps List for 2022.

Grant heat pump advantages

Huge savings on heating costs – Depending on the flow temperature and climate conditions, a superior quality air-to-water heat pump such as Grant’s requires four times less energy than a good quality gas boiler of high efficiency to produce the equal amount of heat. This means lower running costs and subsequently, considerable savings on one’s utility bills. Also, with a Grant heat pump, you’re no longer reliant on fossil fuels and won’t be affected by the ever rising fuel costs.
Reduced carbon footprint – When it comes to heating systems, heat pumps are being touted as the way forward since they are incredibly eco-friendly and require only a small amount of electricity to function. Additionally, all heat sourced by a Grant heat pump happens to be renewable, thereby further reducing one’s carbon footprint.
Financial rewards & extended guarantee – As long as your Grants Aerona³ R32 model is installed by an MCS-accredited installer, you are eligible for payments/reward under the UK government’s RHI (Renewable Heat Incentive) scheme. And these rewards are of a considerable amount and will help to offset the initial high installation cost of a heat pump unit. Moreover, post April 2022, once the RHI scheme gets replaced by the new Clean Heat Grant, one can look forward to receive as much as £4,000 towards the installation of a new air-to-water heat pump.
Finally, under the G1 scheme (rolled out in March 2020 by Grant UK), you can extend the standard 5-year guarantee on your Grant heat pump to a 7-year guarantee as long as you choose an accredited G1 member (the G1 being Grant UK’s installer network) to install your Grant Aerona³ R32 heat pump unit.

Grant heat pump disadvantages

Reduced efficiency below 0°C (compared to ground source heat pumps) – Although Grant heat pumps can operate efficiently at temperatures close to -20°C, the overall heat output comes down with the drop in temperature (since the units depend exclusively on outside air). In comparison, ground source heat pumps are little affected by low temperatures as they have pipes installed deep under the ground.
Additional spending on larger radiators and underfloor heating – The type of heating produced by air source heat pumps (both air-to-air and air-to-water) has a lower heat supply in comparison to gas or oil boilers. This means one will require a larger heat-emitting surface for an equal amount of space heating. Therefore, switching to heat pumps may involve investing in new and larger radiators or installing underfloor heating (if you don’t already have this).
Not enough savings for people having access to mains gas – The difference between the electricity price (for running your Grant heat pump) and the gas price (for those having access to lower-priced mains gas) is not significant enough to justify the high upfront installation cost of Grant heat pumps. That said, the latter are primarily meant for off-grid homes in the first place. Moreover, the government is focused on increasing the installations of heat pumps, meaning one can expect to receive a number of low-carbon incentives at the time of making the switch.

Are Grant heat pumps any good?

As mentioned already, the Grant Aerona³ R32 17kW model has been nominated as the best overall air source heat pump for 2022 by Eco Experts, UK and there are good reasons for this. The 17kW as well as the other three units in the Aerona³ R32 range are favourites among domestic consumers for the superior convenience and comfort levels (low noise, easy installation, low maintenance, ability to work efficiently in extremely low temperatures) the units provide.

Further, the units have the best price-to-efficiency ratio within their category. While most heat pumps’ (excepting the priciest ones) CoP fall between 3.5 and 4.0, the Aerona³ R32 models come with SCoP ratings of 4.62, 5.22, 5.41 and 4.54 for their 6kW, 10kW, 13kW and 17kW units respectively.

As the various government schemes suggest, heat pumps are the future of heating for the UK and Grant’s domestic consumer air source heat pump models are arguably your best bet when considering a switch.

If you would like to find out more about heat pumps for your own home, why not browse around some of the other articles on this website, where you can find out about the different types of heat pump and how they work.

If you’re already keen to get a quote for installation, talking to an expert heat pump installer would be your next step and our article on how to find a heat pump installer gives you information about what to expect and the right types of question to ask.

24 February 2022

Alternative Heating Systems – Efficient, Green Solutions

The current global energy crisis has forced many people in the UK to assess alternative heating systems for their homes.

Even before gas, oil and electricity prices began to skyrocket, many people were investigating alternative heating as a means of reducing their carbon footprint and at the same time save some money.

Government incentives such as the renewable heat incentive (RHI) have seen an increase in the number of people expressing an interest in heat pump technology, solar power and even wind power. But what are the pros and cons of investing in alternative heating systems, and what even are the alternatives? Read on to find out more.

What are alternative methods for heating?

There are many alternatives available for heating your home and providing hot water, from the traditional options such as gas or oil boilers, through wood-burning stoves, to what many people consider truly alternative heating such as heat pumps, solar PV or biomass boilers. There are even hybrid heat pump systems that incorporate renewable heat pump technology with fossil fuel boilers.

These different types of heating fall into two broad categories:

“Traditional” fossil fuel heating; and
“Alternative” renewable heating

There is some grey area in the middle, for example wood-burning stoves do not utilise fossil fuels to provide heat, but depending on whether the wood is sourced from sustainable forestry, how far the wood has to travel from where it is harvested to where it is burnt and whether it has been kiln dried prior to sale, are all factors that can bump up the overall carbon footprint of your wood-burning stove.

Let’s take a look at some of the different methods for heating your home and consider the pros and cons of each alternative heating method.

Traditional heating systems

Traditional heating systems all have the advantage of using well established and proven technology.

Many are based on fossil fuel, which is very bad from an environmental point of view. However, sometimes there is simply no alternative, either for financial reasons or because alternative heating technologies are unsuited to the demands of a harsh climate or particular user needs.

Mains gas

By far the most popular form of heating in the UK, mains gas has earned its number one position at the top of the user charts because of its convenience and affordability. Despite contributing to global warming, many people find that mains gas is just too convenient and too cheap an option to pass up.

At the time of writing the average cost per kilowatt hour of gas in the UK is approximately 3.8p. This is less than a quarter of the cost of electricity. It is very easy to see why this is such a popular choice for many people.

Another great advantage that gas has in his favour is its convenience. At the flick of a switch or the turn of a dial, you can enjoy instant heat. This benefit was drilled home to millions of people during the “cookability” advertising campaign run by British Gas in the 1980s. The cookability adverts featured Noel Edmonds interviewing housewives about how gas was such a good fuel for cooking. If you’re of a certain vintage you may remember these adverts, but just in case you’ve forgotten or are too young to have seen these the first time around, I have embedded an example below.

It is not all positive for mains gas, however, because as I said above it is a greenhouse gas and therefore contributes to global warming.

The current tensions in Ukraine are also highlighting concerns about security of supply and potential increases in price. Although around half of the gas used in the UK comes from the North Sea and a further third comes from Norway, the UK could still be badly affected if Russian gas becomes more scarce.

This is because countries that currently buy a lot of Russian gas would quickly have to find alternative supplies, and would end up competing with the UK for those supplies. This could cause sharp rises in price, which is a potential downside for mains gas.

Mains gas advantages

Low cost per kilowatt hour.
Convenience.
Easily controllable.
Amazing cookability!

Mains gas disadvantages

Fossil fuel – contributes to climate change.
Prices could skyrocket if Russia turns off the tap (or supply is reduced some other way).

LPG gas

If you want to use gas and are not on the mains gas grid, your best bet is to heat your home using an LPG boiler.

LPG stands for liquid petroleum gas. If your needs are modest, you can purchase LPG gas in 47 kg bottles. Each bottle will typically last between six months and a year if you are using it purely for cooking, but if you want to use LPG to heat your home, you’ll need a much bigger tank.

Commonly, a large LPG tank will be provided by your gas supplier, who will normally retain ownership and you will pay a rental fee for the use of the tank. You might be locked into a contract with this gas supplier as well, which might be seen as a downside leaving you with a lack of choice and options if the supplier pushes up prices.

LPG is a fossil fuel, so this is not a particularly green choice. It could also be subject to price rises and the vagaries of the international gas market. The price of LPG gas per kilowatt hour at the time of writing is around 8p, which is about twice the price of mains gas.

LPG gas advantages

Convenient
Despite being more expensive than mains gas, still good value.
Easily controllable.
Can be used for cooking as well as heating (there’s that cookability factor again!)

LPG gas disadvantages

More expensive than mains gas.
Fossil fuel – contributes to climate change
Subject to the same potential price increases as mains gas

Oil fired boiler

Oil fired central heating is another popular choice for people who live off the gas grid. Over 1 million homes in the UK use oil heating, so it’s a popular choice if you’re not on the gas grid.

Oil fired combi boilers are very efficient these days and can achieve over 90% efficiency. Oil tends to be cheaper per kilowatt hour than LPG but oil boilers are slightly more expensive to install than equivalent LPG boilers.

Like LPG, you’ll need a tank to store the fuel. Oil can be delivered by tanker to your property and you can come to an arrangement with your supplier to automatically top up your tank as and when it’s needed. This is normally done by installing sensing equipment in your tank, which communicates with the oil depot to alert them when a top-up is required.

Even if you don’t have sensor on your tank, some suppliers will simply agree to top up your tank whenever they are passing, thereby making sure that you never run out.

Oil is a slightly smellier fuel than LPG for mains gas, but this is rarely much of an issue because your oil tank is generally well away from your house and emissions from the boiler itself are fairly innocuous.

In fact, a heating engineer I know told me that the emissions from an oil fired boiler in the UK have to contain lower levels of carbon monoxide than those that would trigger a carbon monoxide alarm to go off. I have in fact checked this but doubt that he would make that claim lightly.

Oil fired boiler advantages

Low cost per kilowatt hour compared to LPG
Convenient and easily controllable
Modern oil fired boilers are extremely quiet and efficient
Oil fired boilers give very strong performance during cold winters

Oil fired boiler disadvantages

Oil tank can be smelly
Greater the potential for localised pollution due to oil spills
Installation of the boiler more expensive than LPG gas boiler
Storage tank more expensive than LPG storage tank
Fossil fuel – contributes to global warming

Electric heating

Electric heating is a viable way to heat your home if you are not on the mains gas grid, but you really need to think about whether it is suitable for your home before taking the plunge because unless you are careful this can turn out to be quite an expensive option.

Even before the current energy crisis, electric heating was significantly more expensive to run than mains gas heating. With the cost of electricity on the rise, the economics are not working in its favour.

One of the key advantages of electric heating is that it’s a very clean form of heating. There are no emissions from a flue, in contrast to gas and oil boilers, which means you don’t need to think so hard about where to position your boiler or worry about siting it away from windows.

Electricity can also be considered greener as a form of heating when compared to fossil fuel alternatives such as oil and gas, particularly if you are on a green tariff which uses electricity generated from renewables.

The relatively high cost of electric heating can also be mitigated by using cheaper rate electricity. Economy 7 allows you to use electricity at a cheaper rate during a seven-hour period overnight and Economy 10 does the same thing but with an additional three hour window in the afternoon.

In order to take full advantage of the Economy 7 and Economy 10 tariffs, you need to have night storage heaters. Storage heaters contain ceramic, thermal energy absorbing blocks, which store the heat generated overnight and release it gradually during the day.

The rate of heating provided by storage heaters is controlled using adjustable vents which allow more warm air to flow into the room when opened. Some models of storage heater also come with fans to help distribute the heat around the room.

Modern storage heaters also come with all the bells and whistles that we have all come to expect, such as controllability via smart phone controls, automatic timers and thermostats. One of the criticisms of storage heaters in the past was that they were unable to store sufficient heat to keep your home warm throughout the day.

This meant that they would run out of heat energy by evening, just when you wanted your house to be at its cosiest. More modern designs that are cleverer about how the heat is released and innovations in technology that allow more heat to be retained by the ceramic blocks have improved performance so that this is less of an issue these days.

Advantages of electric storage heating

Clean technology
Cheaper to install than gas or oil boilers
A low maintenance requirement
Electric heating is available in areas not served by mains gas
Using green electricity tariffs means electric heating contributes less to climate change
Economy 7 and Economy 10 tariffs allow for maximum efficiency

Disadvantages of electric heating

Relatively expensive when compared to mains gas
Not as controllable as fossil fuel alternatives
Storage heaters can run out of heat towards the end of the day meaning your house might be cooler in the evenings

Alternative Heating Systems

There are many alternative heating systems on the market these days, which can make deciding on the right one for you confusing and difficult.

The UK government is looking to phase out all gas and oil fired boilers for new build homes by 2025. This will help us to achieve our climate change targets but doesn’t really go far enough because it doesn’t tackle our existing housing stock. If we are really serious about tackling climate change, we need to get busy retrofitting existing homes with renewable heating.

But why go to all the expense and disruption involved in replacing your heating system? Well, apart from the warm glow (pun intended) you will get from knowing you’re doing the right thing for the planet, you might be pleasantly surprised to discover that you can save money and have a more convenient, controllable heating system.

The government extended the renewable heat incentive (RHI) to support homeowners who wish to install renewable heating. Given the ambitious targets set, it seems likely that some form of incentive will be available for some time to come.

So what are the options? Let’s take a look at a few of the more popular renewable heating systems available today.

Air source heat pumps

Air source heat pumps make use of the ambient heat available outside to heat your home. It’s difficult to believe, especially in Scotland, but even during the winter there is sufficient heat available in the great outdoors to operate an air source heat pump effectively.

All heat pumps use the refrigeration cycle – a well established scientific process – to gather heat, concentrate that heat and then distribute it throughout the home. They are essentially air conditioning units in reverse.

Air source heat pumps come in the form of a discrete box, which sits outside your home. They can be installed in just a few days and with minimal disruption. Once installed, they run reliably and with very little maintenance being required. It’s a good idea to clean them every now and again and to ensure they get a service every year, however you shouldn’t need to spend very much money repairing or maintaining them.

Air source heat pumps are a very clean way to heat your home because there are no emissions, in contrast to an oil or gas boiler, the exhaust gases from which need to be ejected via the flue.

Because they move heat rather than generate heat directly using electricity, they are far more efficient than traditional electric heating, typically having a coefficient of performance of between three and four. A coefficient of performance of 4 means that for every unit of electrical energy used by the heat pump, 4 units of heat energy is generated.

Such high-efficiency is the reason that heat pumps are classed as renewable energy, which means that they qualify for the government incentives mentioned above.

One important thing that is sometimes glossed over by people keen to promote heat pumps, is the fact that you need to have a well insulated home for them to operate efficiently. Heat pumps operate at lower temperatures than traditional boilers, which can simply be turned up higher in a draughty old house during the winter. If you try to do the same thing with a heat pump, you could find that your electricity bills are rather large, you might even find that your house is a bit cooler than you would prefer.

Air source heat pump advantages

Clean form of heating with zero emissions at point of use
Classified as renewable – contributes less to climate change
Qualifies for the renewable heat incentive (RHI) payment scheme
Relatively cheap installation cost
Low running and maintenance costs

Air source heat pump disadvantages

Appearance of some models not aesthetically pleasing
Could require planning permission in some circumstances
Good insulation is required as a prerequisite, which can be expensive if it needs to be retrofitted
Noise – certain models have been known to be a little noisy, which can cause problems if the unit is installed to close to a bedroom window, for example.

Ground source heat pumps

Ground source heat pumps operate on the same basic principle as air source heat pumps i.e. they absorb heat from outside the building and transfer it to the inside using the principles of the refrigeration cycle.

A refrigerant is circulated around the system and absorbs heat in the evaporator pipework. In the case of a ground source heat pump, this is called the ground loop and is buried underground instead of simply being placed outside your house with a fan blowing air across it.

Once the heat has been collected, it passes through a compressor and then onto the condenser, which rejects the heat and makes it available for the heat distribution system chosen by the householder.

Popular forms of heat distribution include underfloor heating and low-temperature radiators, both of which are ideally suited to the task of warming the home as part of a heat pump system. This is because they both have a very large surface area across which heat transfer can take place, which is necessary due to the low operating temperatures of heat pump systems.

It is important to bear in mind the type of heat distribution that your heat pump system will need, because retrofit of underfloor heating, or replacement of your existing radiators with low-temperature radiators is likely to be very disruptive and expensive.

Installation costs of ground source heat pumps are higher than those for air source heat pumps because of the ground works required. The ground loop has to be buried in trenches in your garden. Again, this is very disruptive and obviously more expensive than simply placing an air source heat pump unit at the side of your house.

It also requires that you have plenty of space available because the ground loop can be quite large. For this reason, ground source heat pumps are not well suited to all properties. On the plus side, more consistent temperatures below ground often mean the ground source heat pumps can operate more efficiently, which makes for lower running costs.

If your heart is set on having a ground source heat pump but you don’t have lots of space outside your house, it may be possible to drill a deep borehole instead of a shallow trench to accommodate the ground loop. If this is what you want to do, it’s important that you get good advice because drilling boreholes can be expensive. The exact cost will depend on ground conditions that are encountered by the drillers but you could easily spend £5000 for a single borehole and chances are you will need more than one borehole to drive your heat pump.

Ground source heat pump advantages

Normally more efficient and cheaper to run than an air source heat pump
No fan blowing air across your heat pump pipework outside your bedroom window
Renewable form of heating – contributes less to climate change
No flue gases generated

Ground source heat pump disadvantages

Ground loop installation is very disruptive
Installation costs tend to be quite high
Insulation to a high standard is a prerequisite

Biomass boilers

A halfway house between a traditional boiler and a renewable heating system, these systems burn wood rather than fossil fuel.

They qualify as a source of renewable heat, despite the fact that they do actually burn carbon in the form biomass. The reason for this is that biomass boilers burn wood pellets, which are either made specifically from sustainably grown wood, or from offcuts produced in sawmills and other wooden manufacturing processes.

The idea is that sustainably grown wood captures carbon from the atmosphere as it grows and I carbon is emitted when it is burnt. The net effect is to not release any additional carbon into the atmosphere.

In the case of pellets made from offcuts, the theory is that burning them in biomass boilers in order to recover heat is preferable to simply throwing them away. Fair point.

Biomass boilers require more maintenance than heat pumps, particularly from the homeowner, who in the case of a manually fed biomass boiler will need to top up the boiler hopper regularly. The amount of effort involved is very similar to that of a wood-burning stove or open coal fire.

In my experience, there’s a fair amount of tinkering needs to be done with biomass boilers to keep them running smoothly. The grate upon which the pellets are burnt needs to be kept clean. Some boilers have an automatic maintenance process to keep this clear of ash, but they don’t always work perfectly so user intervention is often required.

Unless you have a automatically fed boiler, you will also need to hump a load of 10 kg bags of wood pellets into your boiler room every few weeks when the delivery arrives. If you are elderly or just don’t want to have to go to such effort on a regular basis, you’ll want to think carefully about whether biomass boilers are the right choice for you.

Biomass boiler advantages

Carbon neutral
Qualify for money under the renewable heat incentive (RHI)

Biomass boiler disadvantages

Require regular maintenance by the homeowner
Can require manual lifting of pallet bags from your driveway to boiler room
Occasionally get blocked, requiring the homeowner to roll their sleeves up and clear the grate

Solar thermal panels

Solar thermal panels absorb heat energy from the sun and then transfer this heat via a heat exchanger to a central heating system to heat the home, or a hot water cylinder to provide domestic hot water.

It stands to reason that the more sun you have shining on one of these thermal panels, the more efficient and effective it will be. The sun doesn’t always shine in Scotland, unless you live in Dundee that is! However, solar thermal panels still working compliments and when the sky is grey and overcast.

These systems also make use of an energy storage system which means the sun doesn’t need to shine all the time for them to work.

Solar thermal panels tend to be one of two types: either flat plate collectors or the more efficient vacuum tube collectors. Such systems will work best if your roof is south facing, but you can install on the ground if you wish, provided they are away from the shade of trees and other buildings.

Solar thermal is a form of renewable energy, which means you can apply for money via the renewable heat incentive (RHI), thereby bringing down the overall cost.

Solar thermal panel advantages

Require less space than solar PV panels
Simple technology with no moving parts requiring no maintenance
Renewable energy which qualifies for the renewable heat incentive

Solar thermal panel disadvantages

Less efficient during the winter when the sun is less bright
Longer payback period of initial investment

Solar PV

Solar PV panels are a great way to reduce your electricity bills, reduce your carbon footprint and even get paid for the surplus electricity you generate.

They work by harnessing energy from the sun, which is converted to electricity than be used in the home or exported to the grid if it is surplus to requirements.

If you have sufficient space on your roof and it is not shaded, solar PV is an excellent option.

Although the feed in tariff scheme was closed to new applicants in March 2019, a replacement scheme has been created to continue to incentivise the generation of renewable energy on a small scale. This new scheme is called the smart export guarantee (SEG) and is available throughout the UK. The SEG can make a huge difference to the economic viability of solar PV.

Solar PV is relatively cheap to install and requires very little maintenance.

When coupled with other renewable forms of alternative heating, such as an air source heat pump, the benefits of solar PV are multiplied.

Even without being used in combination with other renewable heating, solar PV can save you a significant amount of money. For example, according to the energy saving trust, for a four-bedroom detached property with a hot water cylinder and in the case of somebody who is home all day, savings could be as high as £360 per year.

Solar PV advantages

Renewable energy – does not contribute to climate change
Relatively cheap to install
Low maintenance
Can be used in conjunction with other renewable heating, such as heat pumps

Solar PV disadvantages

Not suitable for shaded areas
Requires significant space on your roof

Summary

There are many alternative heating systems on the market today. Traditional fossil fuel based heating systems are being phased out in favour of renewable systems that do not contribute to climate change.

If your gas or oil boiler is due to be renewed soon, it is worthwhile investigating alternative heating systems because they will reduce your carbon footprint and could also save you a significant amount of money.

Popular alternatives include air source heat pumps and ground source heat pumps, with the former being cheaper and less disruptive to install.

Biomass boilers tend to require more upkeep and maintenance than heat pumps, but remain a viable choice if you want to go green and take advantage of the renewable heat incentive.

Finally, if you really want to demonstrate your green credentials, consider combining solar PV with a heat pump heating system, which will multiply the benefits that either one alone would provide.

If you’ve read this far, you might be interested in our article on how to find a heat pump installer, which will tell you what to look out for and what your next steps should be if you are interested in getting a heat pump installed.

24 January 2022

Health Centre – Ground Source Heat Pump

A specialist company that focuses on commercial ground source heat pumps was asked to provide a turnkey package for the design and installation of a system capable of supplying heating and cooling to a new health centre in the heart of Brighton\Hove.

Using their expertise in designing heat pump systems that provide heating and cooling they were able to store rejected energy from the cooling cycle within the borehole array, which is then harvested during the heating operation. A total of 10 x 100m boreholes were drilled in the car park and distributed from a sealed manifold chamber.

Not only does this increase the performance and efficiency of the heat pump but also reduces the capital cost due to fewer boreholes being required.

From an extensive commercial range they selected the Climaveneta ATV 2020 Ground Source Heat Pump with a BacNet building management interface providing 70kW of heating\cooling.

The heat pump supplies a 1000L buffer tank providing space heating at 45˚C and cooling at 7˚C to the Uponor under floor system.

At time of writing, the Health Centre was in the process of claiming the Non Domestic RHI tariff which would provide a revenue for the next 20 years.

8 December 2021

Ground and Air Source Heat Pump

A specialist firm of heat pump installers were asked to tender for the design and installation of a ground source heat pump system to replace an existing system installed by the market leaders in commercial heat pumps at the time, Earth Energy.

Due to the unknown design and location of the existing borehole array, just replacing the heat pumps like for like was not an option. After conducting a thermal response test on the ground array and careful consideration they came up with not only a design that could utilise the existing boreholes but also provide the total buildings heating load and, importantly, do this within budget.

To backup the design and ensure the boreholes could meet the extraction rates for the heat pump, they conducted a thermal response test on the system. This allowed them to accurately select a ground source heat pump that could operate within the design tolerances. The data collected also highlighted that a second heat pump would be required to meet the buildings heating load. Due to the geographical location and concerns with drilling new boreholes where existing probes are buried, they proposed a cascade controlled system with an air source heat pump.

Using the latest Danfoss Thermia commercial range of ground and air heat pumps they are able to combine the 2 technologies through a Network controlled manager the Danfoss Solution Controller (DSC). The system has been designed to be optimised under part load conditions meaning the DSC will sequence the order and starting of the 2 heat pumps depending on ambient air temperature and the building’s heating load.

13 October 2021

Turnkey Ground Source Heat Pump

Specialists in commercial ground source heat pumps we were asked to provide a turnkey package for the design and installation of a system capable of supplying heating and cooling to this flag ship renewable energy centre in Hayle, Cornwall.

Using their expertise in designing heat pump systems that provide heating and cooling they were able to store rejected energy from the cooling cycle within the borehole array which is then harvested during the heating operation. A total of 8 x 100m bore holes were drilled in the car park and distributed from a sealed manifold chamber.

Not only does this increase the performance and efficiency of the heat pump but also reduces the capital cost due to fewer bore holes being required.

From an extensive commercial range they selected 2No Clivet XENN Ground Source Heat Pumps working in cascade to provide increased part load efficiency. A BacNet building management interface provides remote access to the 80kW heating and cooling system.

The heat pump supplies a 800L buffer tank providing space heating at 45˚C and cooling at 7˚C to the Uponor under floor system.

The building is in the process of claiming the Non Domestic RHI tariff which will provide a revenue for the next 20 years.

9 July 2021

Ground Source Heat Pump Installation

This new build development in Trowbridge was built to the latest building regulations. The Danfoss \ Thermia Diplomat ground source heat pump with an integrated 180L heat pump optimised hot water cylinder was specified. Whilst an air source heat pump could easily have done the job, it was agreed that ground source would be preferred.

This is complemented with a Uponor and Heatmiser wet under floor system using the traditional method of 16mm PEX pipe buried in screed.

Due to the high insulation properties of the building, heating was not required on the first floor but it was suggested that installing under floor heating in diffuser plates for the bathroom would be worthwhile. Who doesn’t like a warm floor in the bathroom?

The Danfoss Thermia range of heat pumps has been specifically designed to maximize efficiency with market leading efficiency and hot water production. The compact design & integrated hot water cylinder make the unit ideal when space is an issue.

Internal modulating circulation pumps maximize efficiency and performance while reducing the annual running cost.

The Thermia Diplomat G2 has market leading hot water production. This is made possible by two technologies;

Hot Gas Water heater, is patented technology that utilizes rejected energy from the heating cycle to produce free hot water simultaneously.
Tap Water Stratificator, is patented technology developed to stratify hot water in the tank to ensure optimum performance and maximise usable hot water.

This system is efficient and unobtrusive, providing hot water and heating living spaces in an environmentally friendly and cost-effective manner for many years to come.

11 March 2021

Geothermal Heating with Geothermal Heat Pumps

Geothermal Energy vs Heat Pump Technology

Geothermal Heating

A quick note about geothermal heating before we start. I want to acknowledge that the term “geothermal energy” strictly relates to the utilisation of heat energy originating from within the earth’s molten core. True geothermal energy systems work by circulating an appropriate fluid (e.g. water) down a borehole so that it is heated as a result of its proximity to the molten rock (or magma) that finds its way up from the earth’s molten mantle into the crust. The heated water can then be pumped to the surface and used to heat houses, offices or for other purposes.

The earth’s crust varies in thickness from around 10km to 70km. The maximum depth of a borehole is usually accepted to be around 15km, which can only be achieved with highly specialised drilling equipment and at great expense. It is not possible to drill into the molten core where the temperature is hottest but this is not necessary, or even desirable, in order to make use of geothermal heat because the crust is heated to a sufficiently high temperature at depths achieved in very deep boreholes or in places where the earth’s crust is relatively thin.

Cooking using geothermal heat in Rotorua

In some locations where the crust is particularly thin, such as Rotorua on the North Island of New Zealand, locals have used this energy to meet their needs for centuries, for example by cooking with the heat energy that makes its way to the near surface of their town.

In Iceland, geothermal heat is used to heat greenhouses that allow crops to be grown that would never otherwise survive in the cold climate. It is also used to heat the many hot springs enjoyed by Icelanders, and provides a fantastic show at the many geysers that bring thousands of tourists flocking to Iceland each year.

So, that’s geothermal heating, how is heat pump technology different?

Heat Pumps

Now that we’ve got the definition of geothermal out of the way, let’s turn to heat pump technology. Heat pumps operate in much the same way as your refrigerator. If you’ve ever noticed that the back of your fridge is warm to the touch, you’ll have experienced the effects of a heat pump. In the case of a fridge, the heat pump takes the heat from the inside and emits it via the evaporator (which acts much like a radiator) on the outside of the fridge (usually at the back).

Thanks to the technology employed in the heat pump, the temperature difference between the cold and hot sides of the pump does not need to be very large in order for effective heating and/or cooling to happen efficiently.

What makes this possible are the particular properties of the refrigerant fluid and how it behaves as it is pumped around the heat pump system in what is called the “refrigeration cycle”. You can read about the refrigeration cycle in detail here, but basically it makes use of expansion, evaporation, compression and condensation in order to move heat from inside the fridge to the outside. A heat pump system does this in reverse, taking heat from outside a house (which in fact originates from the sun) and transferring it to the inside, thereby heating the house. It does this very efficiently, far more efficiently than direct electric heating would do. This is why heat pumps are classed as renewable energy in most countries.

In recent times, the term “geothermal heat pump” has been used, particularly by the uninitiated, to refer to ground source heat pumps. I want those looking for information on heat pumps to be able to find it without necessarily knowing that “geothermal heat pump” is a misnomer, so I have included the above clarification in this article to educate and to inform before providing the information that many will be looking for around heat pumps.

Now that’s out of the way, the rest of this article will deal with “geothermal heat pumps” using that vernacular term, but please bear in mind the clarification above in case you later discuss the subject with a pedant such as myself!

So, what are geothermal heat pumps and where might you find them?

Geothermal heat pumps (GHPs) are among the most efficient and comfortable heating and cooling technologies available, according to the U.S. Department of Energy, because they use the earth’s natural ability to supply or absorb heat at extremely high efficiencies.

GHP systems are commonly used to provide heating and cooling to homes, schools, hospitals, as well as commercial and government buildings.

GHP systems take a fundamentally different approach to heating and cooling than conventional systems. Unlike conventional boilers — which create heat by burning a fuel such as natural gas, propane, or fuel oil — GHP systems don’t create heat, so there’s no chemical combustion.

Instead, GHP systems move heat (thermal energy) stored in the earth or groundwater to the building during winter and remove heat from the building to the earth or groundwater during summer months.

According to the GeoExchange, there are more than 1 million GHP installations in the United States today. While this is a small percentage of the total HVAC market, the number of people choosing to install GHP systems is growing rapidly at a rate of about 50,000 installations a year.

What are the cost benefits of GHPs?

Man counting coins and placing a coin on top of a pile of pound coins

Even though the installation price of a geothermal system is more than that of conventional heating and cooling systems of the same capacity, the energy savings are significant and therefore will offset the higher installation costs over time.

When the cost of a GHP system is included in a mortgage, your investment should produce a positive cash flow from the beginning. In other words, the extra cost of the GHP system to the total mortgage payment will likely be exceeded by energy cost savings over the course of each year.

Learn about various financing options by first familiarising yourself with the Renewable Heat Incentive and consulting the Ofgem website.

Are there financial incentives to installing a GHP system?

Geothermal heat pump systems installed in the UK in new or existing homes by 31 March 2022, are eligible for payments over a seven year period.

To learn more about residential and commercial incentives, click here.

What are the maintenance requirements of a GHP system?

System life is estimated at 25 years for the inside components and 50-plus years for the ground loop, according to the U.S. Department of Energy.

GHP systems have relatively few moving parts and those parts are sheltered inside a building, so the systems are durable and highly reliable. GHP systems usually have no outside compressors, so they are not susceptible to vandalism.

In addition, the components in the living space are easily accessible, which increases the convenience factor and helps ensure that the upkeep is done on a timely basis.

What professionals are involved in GHP systems?

Depending on the size and complexity of a GHP project, multiple professionals may be involved. Large institutional, commercial, or industrial GHP projects could involve as many as 15 different types of professionals, such as those who:

Design and engineer the systems
Install system components
Inspect and regulate the systems.

For residential GHP systems, one contractor with the necessary credentials may design and install the entire system. To learn more about choosing and installing a geothermal heat pump system, read this article.

Can a GHP system be installed for any type of building?

There are four basic types of ground loop systems. Three of these—horizontal, vertical, and pond/lake—are closed-loop systems. The fourth type of system is the open-loop option. All of these approaches can be used for residential, commercial, and institutional buildings such as schools or government facilities. Which GHP option is best depends on the climate, soil conditions, available land, and local installation costs at the site.

Most closed-loop geothermal heat pumps circulate an environmentally friendly antifreeze solution through a closed loop—usually made of plastic tubing—that is buried in the ground or submerged in water. A heat exchanger transfers heat between the refrigerant in the heat pump and the antifreeze solution in the closed loop. The loop can be in a horizontal, vertical, or pond/lake configuration.

Closed loop vertical ground source heat pump.

An open-loop system uses well or surface body water as the heat exchange fluid that circulates directly through the GHP system. Once it has circulated through the system, the water returns to the ground through the well, a recharge well, or surface discharge. This option is practical only where there is an adequate supply of relatively clean water.

A fifth type of hybrid heat exchanger is called a “standing column”—a system using a single water well for both extraction and return of groundwater for a ground source heat pump. Water may be discharged from the well to maintain operational groundwater temperatures.

GHP case studies

Click here to view case studies of GHP projects and energy and cost savings.

If you are lucky enough to have access to true geothermal energy and perhaps have already installed geothermal heating in your home, I’d love to hear from you.

If like most of us here in Scotland you are confined to heat pump technology (still absolutely viable as a source of heat), you might be interested in our article on how to find a heat pump installer.

9 December 2020

Thermia Ground source heat pump – New Build – Domestic RHI

Specifications

This exclusive new build development in Cornwall has been built with no expense spared. To meet the standards required for an A rated energy efficient house a Thermia ECO 42kW ground source heat pump with 8 x 100m vertical boreholes distributed from a sealed manifold chamber. The heat pump supplies a 500L heating buffer tank and 2 x 250L heat pump optimised hot water cylinders. The buffer tank supplies the wet under floor heating system and indoor swimming pool.

Ground Collector

The ground collector is flushed and filled with a diluted Ethylene Glycol mixture (20%). THERMOX DTX has been tested and classified as Non-Toxic 1 by an EPA 2 certified Laboratory. There is plenty of space on the site, so the ground collector had no limitations or problems in that regard.

Instant Hot Water

The heat pump is capable of storing domestic hot water at 60˚C with a secondary return that pumps the hot water around the building meaning you have instant hot water at tap outlets. This is the next best thing to having a true geothermal “heat pump”, like the ones they have in Iceland.

Efficiency

To increase system efficiency and performance, the Thermia Solution Controller has been specified. The web based user interface allows remote monitoring of the system with;

• Access to control strategies and interface parameters
• System overview
• Datalogging with presentation in graphical charts
• Alarm notification through e-mail or SMS

Aftercare

Due to the varying load conditions during the `bedding in` period (12 months), the company who installed this system provided a free service where they monitored and optimised the system remotely.

Domestic RHI Payments

As this is a self build the client was entitled to the Domestic RHI which would generate a revenue of £40,000 over the next 7 years. All things considered, this results in a significant saving, in line with or better than similar heat pump systems that have been retrofitted on older properties.

3 September 2020

Advantages of Heat Pumps

Despite a number of heat pump misconceptions there are many significant advantages of heat pumps ranging from reduced running costs and excellent efficiency gains to combining with Underfloor Heating systems. Below are just a few heat pump advantages for you to consider.

Using Heat Pumps to reduce running costs

One of the advantages of heat pumps is that because they move heat rather than creating it by burning oil or gas, they are much more efficient with average savings of over 60% for ground source heat pumps (almost as much as geothermal heat pumps) and 40% for air source heat pumps. As a result, a heating system using heat pumps will provide a realistic return on investment over a much shorter period of time.

Combating unstable oil prices

Oil prices are susceptible to large price hikes, particularly during the winter when you need your heating the most. Heat pumps totally remove this problem providing cost-effective, reliable heating whenever you need it. Heat pumps also remove the dependency on unreliable fuel deliveries which can be further delayed during adverse weather conditions – just two more examples of the advantages of heat pumps.

Increased efficiency

The efficiency of heat pumps is beyond question. For every 4kW of heat moved into your house via ground source heat pumps, only 1kW of electricity is consumed. This gives a perceived efficiency of 400%, sometimes stated as a Co-efficient Of Performance (COP) of 4:1. In the case of air source heat pumps, you can expect a COP of 3:1 which while slightly lower, is a still a huge improvement on boilers which have only around 75% to 80% efficiency rates over their lifespan truly demonstrating the advantages of heat pumps*.

*It’s worth remembering that to get the most efficiency from your heat pump, it pays to make your home as well insulated as possible. Less well insulated homes may not achieve the highest COP levels. COP levels will also depend on the emitter system (radiators, etc) installed.

Grant schemes for Heat Pumps

There are a number of renewable energy grants which you may be able to benefit from when installing heat pumps including the Renewable Heat Incentive (RHI).

The Renewable Heat Incentive (RHI)

The Renewable Heat Incentive (RHI) which launched in April 2014 aims to provide further air source heat pump advantages and ground source heat pump advantages by making payments to owners of these systems for the energy they produce, much like the Feed-in-Tariff for Solar Photovoltaic (Solar PV) systems. Payments are tax-free, index-linked and last for a period of seven years.

No scheduled maintenance

Heat pumps are extremely reliable with minimal regular maintenance required. Our heat pumps have a planned life span of 25 years with no loss of efficiency which again demonstrates one of the many advantages of heat pumps especially when compared to boilers which can lose up to 2% efficiency for each year of operation and have a usable life span of only around 12 years.

Warranty

Another of the advantages of heat pumps is that because they are a well-established technology, many manufacturers offer a 5 year parts and labour warranty on ground source heat pumps which is separately bonded by independent insurance giving you even more peace of mind.

For additional peace of mind, flexible warranty and service options are available beyond the length of the standard warranty period.

Lower environmental impact

Coupling your heat pump to a green electricity supply such as solar photovoltaic (solar PV) can provide your heating, hot water and electricity demands with zero Carbon Dioxide emissions.

Another factor worth mentioning here is the benefits to local air quality. Particularly switching from, say, coal will significantly improve local air quality. If you’ve ever walked down the street on a winter’s morning in an area where most people use open coal fires to heat their homes, you’ll have noticed the acrid smoke that lingers in the air. Not quite as bad as the “pea souper” smogs that used to be commonplace in our major towns and cities in the olden days but still unpleasant.

Some people have drawn attention to the noise that air source heat pumps can make. However, the noise is no louder than a standard combi boiler and its impact can be mitigated through correct siting of the unit and appropriate sound proofing.

The safety advantages of Heat Pumps

People often don’t consider the dangers that conventional heating systems could pose, particularly as the systems age. Heat pumps can eradicate these issues as they don’t use volatile or combustible substances.

Low risk of accidents

Almost 150 people a year are killed by home explosions and carbon monoxide poisoning linked to faulty boilers. Heat pumps are completely free from any contaminants which may cause harm to the environment and they do not emit any noxious gasses which could harm you or your family.

Hot water safety

On average nearly 600 people a year suffer serious scalds from hot water and radiators. Most people don’t realise:

Hot water at 70˚C takes less than half a second to burn
Scald burns are the third most common reason for admission to hospital for under 5’s
7 children a week require hospital treatment involving painful skin grafting and permanent scarring

Easy installation

Any competent plumber can install your heat pump and in case you have any queries, there are many good maintenance and installation companies out there.

So, if you’re interested in finding out more and possibly installing your own heat pump, please get in touch for a quote.

2 September 2020

Groundworks for Heat Pumps

The groundworks for heat pumps are a vital part of any heat pump installation. There are many misconceptions surrounding how such systems should be installed and a number of these focus on what is required in relation to groundworks – hardly surprising considering that this element is hidden from view in the finished installation.

The aim of this article is to provide clear information on the options available to help you choose the best and most cost-effective solution for you, although it’s important to remember that the options will vary depending on the amount of land and the budget available.

Groundworks for Heat Pumps – The Ground Loop

The main objective of the groundworks for heat pumps is to accommodate the ground loop. The ground loop is a series of pipes buried in the garden where the temperature is fairly constant between 10˚C and 13˚C. The ground loop contains a water and glycol (a type of antifreeze) mix at a low temperature which is gently warmed by the surrounding soil (not to be confused with geothermal heat pumps, which make use of the volcanic core of the earth) and in this way, captures the heat which is used by the heat pump.

Straight Ground Loops

The simplest ground loop method consists of a single straight out and return line. It often consists of several loops brought together with a manifold which is known as a Straight Ground Loop.

Slinky Ground Loops

Slinky ground loops are most typically specified for ground source heat pumps as they reduce the amount of land needed. A loop is created meaning energy is extracted from a smaller area. It’s therefore very important to know how to plan the groundworks correctly in order to make best use of the stored heat within the ground and ensure it is not depleted.

It is essential to get good advice from a company that has been installing heat pumps for many years, with plenty of previous projects under their belts to make sure they are well placed to offer the best advice and support. This will give you peace of mind that the ground loop has been specified and installed correctly for the most efficient results.

Groundworks for Heat Pumps – Boreholes

As an alternative solution to slinky or straight ground loop systems, boreholes are another method employed, particularly when very little land is available. The borehole is designed and specified to provide sufficient energy collection from the ground to allow the ground source heat pump to operate efficiently.

The location of the boreholes is always site specific and the depth of the borehole will be dependent on several variables including the heat load of the house and the geology of the ground. Extensive experience is required to ensure that all relevant factors are taken into consideration during the specification process. Often, geological surveys are also undertaken to determine exactly what is required for your project giving you the confidence the groundworks and system as a whole have been correctly specified throughout.

You can find more information about boreholes on our Boreholes for Heat Pumps page.

19 July 2020

Lifting the Lid on Ground Source Heat Pumps

We believe that heating systems using ground source heat pumps to provide all your hot water and heating needs without requiring expensive, regular maintenance checks and which are safer than traditional, volatile, fossil fueled heating systems, are the future of heating in the Scotland.

What are ground source heat pumps?

Ground source heat pumps are renewable energy products which use stored solar energy or ‘ground source heat’ to provide heating and hot water as an alternative to dangerous and expensive fossil fuels. Geothermal heat pumps use the heat from the earth’s molten core but alas that option is not open to those of us who live in Scotland.

One of the advantages of heat pumps is that they can be combined with other systems such as Solar Photovoltaic (Solar PV) and Underfloor Heating systems to provide even greater benefits.

Why ground source heat pumps?

There are many reasons why you might consider ground source heat as a way of heating your home but here are three of the most important:

Cost

With fuel bills and energy prices spiraling out of control, you are looking to save a significant amount of money on the cost of heating your home. Ground source heat pumps can enable you to do just that.

Constant, reliable heating

You want to ensure your home is constantly warm when you need it most and not be at the mercy of unreliable deliveries of coal or oil. By using ground source heat you can future proof yourself against rising bills and supply issues.

The environment

By using a ground heat source to provide the energy for your heating system, you can help do your bit for the environment as ground source heat pumps produce no harmful carbon emissions.

The advantages of heat pumps are significant for most homes in the UK, however, it’s important you understand how this type of heating works and what is involved to capture ground source heat.

How do Ground Source Heat Pumps work?

There are many heat pump misconceptions which can sometimes leave people feeling confused as to how ground source heat pumps work. However, put simply, this type of heating pump moves stored solar energy, sometimes referred to as ground source heat, into the home to provide a total solution for domestic hot water and all heating needs.

Overview

Ground source heat pumps not only make use of renewable energy in the form of ground source heat, they do so in a highly efficient manner.

As heat pumps simply move energy rather than creating it by burning fossil fuels, they are capable of producing up to 4kW of heat using just 1kW of electricity. This gives a potential efficiency of 400%, sometimes stated as a Co-efficient Of Performance (COP) of 4:1*.

Collecting the heat

Collection of this ground source heat is achieved by installing a series of pipes (a ground loop) in the ground which contain a water and glycol (a type of antifreeze) mix at a low temperature. Pipes can be laid in trenches or using boreholes for heat pumps. The surrounding soil is at a higher temperature, typically 10˚C – 13˚C which gently warms the glycol mix as it is pumped around the ground loop.

A temperature increase within the ground loop fluid of just 3˚C or 4˚C is all ground source heat pumps require. The returning warmed liquid is fed into a Heat Exchanger / Evaporator. You can find out more about this process on our page covering groundworks for heat pumps.

The Evaporator

The purpose of the Evaporator within the heating pump is to take the collected ground source heat out of the ground loop liquid and return it cooled to the pipe for the next cycle. It does this by using a refrigerant that boils at approximately -10˚C. The act of boiling turns the refrigerant into a vapour which is then moved into the Compressor.

The Compressor

The Compressor does exactly what the name suggests: the vapour is compressed in volume and as its volume reduces, the temperature increases to levels of between 75˚C and 125˚C. The gas is then fed through a Heat Exchanger within the heating pump.

The Heat Exchanger

Feeding the hot gas through a condenser allows the refrigerant to turn back into a liquid. As it condenses, its heat is passed into the Heat Exchanger which supplies the domestic hot water and powers the central heating system using the ground source heat extracted originally.

The Expansion Valve

To complete the closed circuit of the ground source heat pump, the only thing which needs to be done is reduce the pressure of the condensed liquid. This is achieved via the Expansion Valve.

*It’s worth remembering that to get the most efficiency from your heat pump, it pays to make your home as well insulated as possible. Less well insulated homes may not achieve the highest COP levels. COP levels will also depend on the emitter system (radiators, etc) installed.

What Next?

So, now you know a bit about ground source heat pumps, how they work and what advantages they bring over other options. If you are keen to find out more, try reading up on space requirements or other info on our site.

If you are keen to speak with a qualified professional about getting your own heat pump system installed, take a look at the list of installers on our “find an installer” page.

4 August 2019

50% Cost Saving with a Ground Source Heat Pump

John and Hazel Hunter installed two ground source heat pumps in autumn 2009. They own a Tower House in Central Scotland, which presented some challenges to the project, partly because of its location but also because of the fact that it is an A listed building. An A listed building is roughly equivalent to a Grade 1 listed building in England, so you can imagine that integrating modern heat pump technology into the historic building in a sympathetic way that kept them on the right side of the authorities was a tall order.

The project was a great success and exceeded their expectations in terms of practicality and cost.

Project Details

The property is a detached tower house in central Scotland and the pre-existing heating system ran on LPG. Several options were considered for the new heating system, some of which were ruled out very early on after initial feasibility assessment. The replacement heating system would be powered by two IVT HT Plus E11 ground source heat pumps and the heat would be distrubuted via radiators.

The project began in September 2009 and was completed by November 2009, a period of three months.

The couple applied for Renewable Heat Incentive (RHI) benefit and the payment levels vastly exceeded their expectations.

Why Heat Pumps?

John and Hazel decided to look at alternative ways to heat their property because the price of LPG was on the rise. An air source heat pump could have done the job but, one evening, sitting in front of the television, they saw a property very similar to their own on the Channel 4 programme Grand Designs. Kevin McCloud was waxing lyrical about the merits of the project, but by far the most interesting aspect to the Hunters was the heating system, which comprised ground source heat pumps.

The Installation Process

The installation process took quite a long time – almost three months, partly due to problems with the ground works.

The installation required more than 1,400m of 40mm pipes, 100m of which had to be lagged with insulation material and be buried a metre deep below the surface.

The house sits immediately on top of a rocky outcrop so getting to a depth of a metre required digging through the underlying bedrock at points. Although there was no convenient body of water to allow installation of a water source heat pump, fortunately, the rock below the property was shale bearing sedimentary rock, which was easily removed with a mechanical digger.

Once the pipes had been laid below ground, the LPG boiler was removed and the new heat pump system was retrofitted to the old pipes and radiators.

The Result

Living with the new heat pump

The couple are very satisfied with their new heating system. Despite a few teething problems caused by dirt getting into the system, which were quickly resolved, things are now running smoothly.

There have been three breakdowns but due to the fact that they have two separate pumps controlled by a step controller, they have never been left without heating. This is a concept called redundancy, which means there is always a backup available.

Renewable Heat Incentive

The Hunters applied for the RHI payments, a process that they found very straightforward, except for the unforgiving nature of the Ofgem website and the somewhat bureaucratic nature of the process, particularly the rigid interpretation of the SPS calculation.

However, it was all worthwhile because the level of payment they will receive has exceeded their expectations hugely.

Impact on Heating Costs

The heating bill for the couple halved overnight. The cost of the excavations was considerable due to the need to dig through bedrock, coming in at around £35,000, however, the payback period of this initial investment is just 10 years, even without taking the RHI payments into account.

Benefits of Ground Source Heat Pumps

The cost benefits speak for themselves – who wouldn’t enjoy having their heating bills halved at a stroke? Yet that’s exactly what the Hunters have had happen to them.

The house is warm all the time the heating is running, which is the case for around 9 months of the year. The system also has an auto-adjustment feature to account for times when the outside temperature is particularly cold.

Due to the colder climate in Scotland compared to other parts of the UK, a water source heat pump can sometimes be a good choice, as has been proposed near the River Tay, but the ground source system installed by the Hunters is doing fantastically well and there seems no reason to change.

4 August 2019

Boreholes for Heat Pumps

When embarking upon a project to install a ground source heat pump, one has a decision to make about the orientation of the ground loop. There are a couple of different options available for the installation of the pipework or “ground loop” which collects the stored solar heat used by heat pumps. The first option would be a shallower, slinky or straight ground loop where the pipes are laid in trenches beneath the ground, or if space is at a premium, there is the more expensive option of using boreholes, which can be drilled straight down into the ground. Of course, if we had more volcanic activity in Scotland, we could take advantage of geothermal heat but that’s sadly not an option in this part of the world.

Specification and location

Boreholes for heat pumps will have been designed and specified to provide sufficient energy collection from the ground to allow the system to operate efficiently. Careful planning is required to ensure that the borehole is installed according to the manufacturers design and it is recommended only to deal with drilling companies who are affiliated to the British Drilling Association providing you with greater confidence that the drilling process is being conducted by true professionals.

The depth of the borehole will be dependent on several variables including the heat load of the property and the geology of the local ground, both of which should have been established by a qualified professional during the project specification and site survey. The location of boreholes for heat pumps is always site specific and must be determined during an in-depth planning process.

Drilling

There are several types of drilling rig available, which are better suited to different ground conditions and can be of varying sizes to accommodate the drilling of boreholes from the smallest gardens right up to the biggest building sites. A common technique is a rotary drill, where the rig rotates drilling rods into the ground, cutting their way as they go. This method is relatively clean, although there will be some spoil and a little water discharged, though this should be cleaned up by the drillers before they leave site. Using this method of drilling can be fairly quick, with progress of between 50 and 60 metres per day, depending on the underlying geology.

How many holes, how deep and how big?

The specification of the boreholes for heat pumps is usually calculated using software that takes into consideration the size of the heat pump, the geology of the ground and the heat losses of the house or building. Boreholes will usually be between 60 and 120 metres deep and may consist of any array of anything between 1 and 12 boreholes depending on the project size. A standard borehole is approximately 120 – 150mm in diameter.

What goes in the borehole?

Once the drilling of boreholes is completed, the borehole loop is inserted into the hole. This loop consists of a pair of plastic pipes that are joined together at the bottom by a ‘U’ bend. This bend is joined by a method called electro-fusion welding and is manufactured and tested in the factory. Once the loop has been lowered into the hole it must be filled with water and pressure tested.

Backfilling the boreholes

As soon as the borehole loop has passed the pressure test, the hole is backfilled. It is important that the backfill material is the correct type and that it fills the hole completely. This is achieved using a natural clay compound called bentonite, which is mixed with water into the bottom of the hole and then solidifies over time. When finished, all that remains will be the tails of the pipe protruding approximately 500mm from the ground. The drillers will attach end taps to these pipes to protect them. This then leaves the boreholes for heat pumps ready for connection to the manifold by others.

A professional company should provide a fully project managed service to meet all your project requirements ensuring the work is professionally undertaken and completed to an exacting standard.

You can use our online directory to find an installer for your own heat pump project.

24 April 2019

How Much Space Is Required for a Ground Source Heat Pump?

Top Takeaways

A horizontal ground loop is usually buried about 2 metres underground.
On average, the ground loop is approximately 200 metres long.
The space requirement for installing the ground loop is about 700-800 square metres.
A slinky arrangement can save space, as can drilling vertical boreholes instead of horizontal trenches.
Vertical boreholes for a ground source heat pump will need to be around 60m deep and will cost more than horizontal trenches.

With the rise in popularity of renewable energy, ground source heat pumps have turned into a very intriguing option for a lot of homeowners. People all over the United Kingdom are interested in the ability to stay warm in the winter months and cool during the summer, without the need for a boiler or air conditioning.

A ground source heat pump is a solution for homes that transfers heat between home and the ground. By moving heat from one space to another, the temperature inside the home can stay optimal. This comes in particularly handy during the coldest months.

But how much space does such a system take up?

Getting a ground source heat pump sounds like a great idea, but what exactly goes into the process and how much space do you need to take advantage of it? Here’s a closer look at the space requirements, plus some common questions and answers in regard to this heating and cooling technology.

Having A Ground Source Heat Pump Installed

Once a person decides on going forward with a GSHP, the design and installation process begins. Companies will often suggest taking the energy from the water going through the pipes in the ground, partly because this offers a stable source of heat, as opposed to an air source heat pump, which is subject to the vagaries of the UK weather.

These pipes are usually about two meters deep, but an alternative is to use vertical boreholes if space is of a premium. This is similar logic to the idea that in crowded cities, where space is at a premium, the only way to build more accommodation is to build up – hence the high-rise blocks of flats in many UK city centres. However, in the world of the ground source heat pump, the only way is down…

Groundwater tends to remain at a fairly constant temperature of approximately 11°C all year round in the UK, which gives enough heat for a heat pump to extract and deliver to your home.

One of the most important parts of the design process is to match the ground loop to the heating load of the home. Inappropriate design can result in poorly-sized systems that fail to do their job properly. This can result in a system that is expensive to run or, in the worst case, one that fails to provide sufficient heat energy to keep the property warm.

After Installation

While the installation process can seem complicated, the result is a very efficient, easy-to-use system for controlling the temperature of your home. The installation process should always be done by professionals, although some people will try to tackle things by themselves. Beware of this temptation! Without the proper knowledge, you can find yourself landed with an expensive and ineffective system. If in doubt, get the professionals in.

Once up and running, the system can be operated without a lot of baby-sitting from the homeowner, so there is not really much to do after installation. There are basic maintenance checks that should be done from time to time, and routine servicing is a very good idea, but mostly installations work as they should for years.

Common Questions and Answers

Since ground-sourced heating and cooling, and sustainable energy as a whole, is still relatively new, many home owners around the UK have questions before they take the plunge. Below are some of the most common questions, with answers provided.

Do you need planning permission for a ground source heat pump?

Most home owners will not need permission, but it is always encouraged for people to look into their own unique situation individually. The majority of homes will be allowed it as permitted development.

Those living in a listed building, or a conservation area, need to look into applying for a permit before installation. Every area is going to have slightly different rules and regulations though, so there is no blanket yes or no answer.

What’s a typical ground source heat pump pipe length?

Ground loops range in size but are typically going to be about 200 meters long. Since many homes will need two or three, with separation between each of them, it is recommended to have about 700-800 square meters to operate with.

This can be a lot of space for a homeowner to have to find, but there are some alternatives. A slinky-like setup needs less space because this allows for installation of a length of pipe in a smaller area but can be less efficient because of the loops transmitting heat between each other underground. Vertical boreholes are another option, but they can be costly due to the drilling process requiring specialist equipment and being more energy and time intensive.

Inside the home, there will be no difference. The entire setup will take up about the same amount of size as a traditional heating and cooling unit.

How deep is a ground source heat pump?

For horizontal loops, the ground is only dug up a few meters. For a vertical loop, most will need to dig at minimum 60 meters.

What are some ground source heat pump advantages?

Operational costs for a ground source heat pump will be pretty low, which is a major advantage for home owners once things are set up and used consistently. The cost stays low thanks to only the compressor needing electric energy. The heat pump is more efficient than a pure electrical heater would be and this is one of its great strengths.

Another advantage is that a GSHP can work for cooling and heating needs. With other setups, a separate air conditioner and boiler are needed. For a GSHP to work for both, the valve just needs to be reversed to change the circulation of the fluid.

Finally, the value of a property can go up with a properly installed ground source heat pump. Since installation is the biggest cost, having one already set up in a home will be beneficial when selling.

And don’t forget government grants and financial incentives, such as the RHI, which can tip the balance in favour of a heat pump system, especially over the lifetime of its operation.

What are the disadvantages of ground source heat pumps?

As mentioned earlier, perhaps the most significant disadvantage is the installation cost. It costs considerably more than putting in a standard conventional boiler or air conditioner. This initial investment is tough for some people to handle, but in the long run, things often more than even out, especially if you qualify for the financial incentives mentioned above.

It can be challenging to find groundwater for a deeper system in specific locations as well, such as in areas of Scotland underlain by hard rock such as the Highlands. That can be a problem for some homeowners in those parts of the country. It is important to research each specific situation first before fully committing. There are alternatives you could consider if you don’t have the option to drill a borehole, such as an air source heat pump.

Any DIY ground source heat pump tips?

For the vast majority of people…don’t try. The installation process is somewhat complex, and if done correctly, it can last a long time. Unless a person has experience with geothermal systems, it’s better to leave it up to professionals.

Those who know enough to try installing a system themselves will not pick up anything useful from this basic overview. They will already know more than enough to tackle a project of this size.

Final Thoughts

There is little doubt that a ground source heat pump can provide a lot of benefits for a home. Not only can it save on monthly bills, but by using renewable energy, it is much better for the environment. It can be a pretty big commitment to get it up and going initially, but the pay-off in the long run can be excellent.

20 December 2016

Ground Source Heat Pump Problems

Things to Look Out For and What To Do If The Worst Happens

Ground source heat pump problems can be avoided if you have your system sized and installed by a reputable company that knows what it is doing. However, you might find yourself stuck with a poorly performing or malfunctioning system for any number of reasons. For example, you may have inherited the system from the previous owner, or perhaps you tried to cut corners yourself on the installation and are now regretting it.

Whatever the cause of the problems you are facing, rest assured that there is almost always a solution. This guide will help you troubleshoot the problems yourself initially and, if professional advice is required, tell you the right kinds of questions to ask of the technician who comes to investigate.

The Heat Pump System

Before we get into talking about the problems that can crop up, its worth spending a little time refreshing our minds about how a ground source heat pump works and the component parts that make up the whole.

A typical ground source heat pump system comprises the following parts.

The Ground Loop (the bit where the heat is sourced)
The “Heat Pump” itself – the mechanical heat engine part that serves as a fridge in reverse
The Heat Sink – e.g. your underfloor heating coils

These are the main bits of the system that you would need to look at to fix any problems and it is useful to bear these pieces in mind as you read on.

If you are keen to go into more detail, you can find more in depth articles elsewhere on this site.

Do you need a professional?

Depending on your level of knowledge and technical competence, you might need to consult a professional at some stage. However there are some basic checks that even a complete lay person can easily carry out. Let’s start with those.

Customer-Led Troubleshooting

Before you reach for the phone, its a good idea to investigate the problem, if for no other reason than you will be better able to describe what has gone wrong to the technician so that he or she can be prepared when they visit you.

Is the system plugged in and receiving power? Obvious I know but this can be overlooked quite easily. The potential embarrassment (and cost) when the engineer comes out, plugs the unit back in and then goes on his merry way having charged you a nice callout fee is worth avoiding.
Visual check. You might be surprised as how much you can find out just by looking in the right places. If something looks wrong, the chances are that it is wrong! So, check for leaks, worn or broken cables and other signs that something is amiss with your system.
Has your circuit breaker tripped? This is a very obvious thing to check and could save you having to go any further with your investigations. Just flick the switch on the breaker back into the “on” position and you’re back in business.
Have you set your system thermostat correctly? It is possible that you, a small child or a pet has accidentally knocked the thermostat and caused it to set the operating temperature to something that you don’t want. I’ve also seen heat pumps put into reverse by mistake (cooling instead of heating), so this is also worth checking.
Is water flowing through the heat exchanger? You can tell this by listening carefully or by touch.
Does your air filter or the coils require a change? If they have become dirty, this can impede the flow and cause your system to malfunction. Give them a clean or change them for new ones.
Is the pressure high enough in the loop system where the heat is absorbed or emitted?
Are the pumps operating correctly? A failed loop pump will cause the entire system to fail.

Professional Advice

If you’ve checked all of the above issues, then it’s time to get a professional on site. Make sure you find a trusted service engineer (personal recommendations are often the best way to ensure that the quality of the technician’s work will be of a high standard).

Some of the issues that might require professional intervention include the following.

Refrigerant problems. The refrigerant is the fluid that does all of the hard work inside your heat pump, so if there’s something wrong with that, it is likely to affect your system as a whole. Typical problems could include low refrigerant levels, scale or fouling of the heat exchanger or a problem with the reversing valve.
Warm air not warm enough. A common cause of this problem is that the flowrate of the air through the system is too high. This means that the residence time of the air is too short and it doesn’t get heated up enough. This problem is normally easily fixed by reducing the speed of the fan.
Generally reduced performance. Less than expected heating or cooling performance is often caused by reduced airflow and can be fixed by replacing the air filter.
High humidity inside the building. This is sometimes caused by an excessively high air flowrate or by the heat pump unit being too big for the job. Adjusting the speed of the fan can often resolve this issue.

If you do find yourself having problems with your ground source heat pump system, don’t panic. A careful visual check can sometimes resolve the problem.

And if you keep your heat pump regularly serviced, it should last you a long time.

If problems persist, obtain the help of a professional. Don’t forget that most companies will guarantee their work for a period of time. Make sure you use a reputable company, preferably based on personal recommendations and you will be fine.

13 July 2016

How Much Does a Ground Source Heat Pump Cost?

Ground loop diagram — Representation of a ground source heat pump system.

Ground source heat pumps are growing in popularity as more people want to do the right thing for the environment. They are not necessarily the cheapest option, but look beyond the initial price tag and consider the longer-term savings before making your decision.

So, what do you need to consider?

Remember to include all the costs and savings

Cost is clearly an important question when you are looking at the different options for heating your home or commercial premises. Ground source heat pump costs can be deceptive because they require a larger upfront investment than some other forms of heating.

But don’t be too short-sighted in your calculations, because although the upfront costs can be considerable, ground source heat pumps often operate more efficiently than some of the other options available, which translates into savings down the road. Payback periods for ground source heat pumps can be as quick as 4 or 5 years.

How price sensitive are you?

Be clear from the beginning about how much contingency you have allowed in your heating budget. If you are very sensitive to increases in your budget, you could be exposing yourself to risk if there are complications with the ground works. Ground source heat pumps require pipework to be installed underground, and until the hole has been dug, there is no cheap and reliable way to establish exactly what is down there.

For example, bedrock could be very shallow, making it harder to excavate the trench for the pipes comprising the heat collection system (called the ground loop). Or in the case of a borehole, you might find yourself dealing with unstable ground conditions requiring more support for the borehole than was anticipated. Then there’s always the risk of encountering unexpected services such as sewer pipes or electricity cables, which can get in the way and, if you are unlucky it’s possible that these could be damaged, resulting in expensive remedial work. However, if you use a trustworthy contractor this shouldn’t be an issue.

At least with an air source heat pump, or even a conventional fossil fuel fired boiler, you will have a good idea how much it will cost to install. There are fewer variables that could cause difficulties and higher costs, which make them a safer option if your budget is constrained.

How “green” are you?

An important consideration that doesn’t get talked about very much is how committed you are to a heat pump system. If you are passionate about the technology itself or the benefits that it offers in terms of reduced environment impact, then you will probably be prepared to pay more compared to someone who is just interested in the savings that a heat pump system can offer.

Remember the grants that are available

The Renewable Heat Incentive (RHI) scheme is a government scheme that pays people for generating heat from renewable means. The scheme is run by Ofgem (the Office of Gas and Electricity Markets), which is a non-ministerial government department and an independent National Regulatory Authority. Ofgem protects the interests of gas and electricity consumers and pays those who generate heat under the RHI scheme using the Treasury’s funds.

The payment per kWhr for the generation of hot water and heat under the RHI depends on the size and specifics of the system being used. It will normally be a few pence per kWhr, which doesn’t sound like much, but you might be surprised to know that, over the course of the 20-year life of the payment, a typical system makes a profit, which brings me to my next point.

Don’t forget to factor in the savings over the lifetime of the system

A typical ground source heat pump system will last more than 20 years, which is plenty of time for the savings made on the running of the system compared with a combustion-based system to offset the installation costs. Look at the entire life cycle of the system to understand the overall savings or indeed profits that will be made by the system.

So how much will a ground source heat pump typically cost?

The answer is obviously, “it depends”, but as a general indication, the estimates given below should give you a rough idea. They are broken down into upfront and running costs.

Upfront Costs

Upfront prices for a 10kW system can range between £6,000 and £15,000. This price bracket doesn’t include the connection to the distribution system, which is obviously different for each building and location.

Running costs

Again, running costs will vary according to a number of factors, the most obvious being the efficiency of the heat pump system. Efficiency is normally stated as the coefficient of performance (CoP). The CoP is simply the ratio of units of heat output to the units of electricity used to run the system.

Typically, most systems will have a CoP somewhere between 3 and 4. This is influenced by the difference in temperature between the heat source (the ground loop) and the heat sink (your heat emitters, such as radiators or underfloor heating).

The highest efficiencies will be achieved by low temperature applications such as underfloor heating, particularly if the climate is releatively mild, or if geothermal energy is producing high temperatures in the ground loop (e.g. a hot spring).

Conversely, heating hot water for use in showers, baths etc will result in lower efficiencies. Better efficiencies are always achieved by low temperature applications.

To give a rough guide, a system running at a CoP of 4 would result in 4kWh of heat being produced for each kWh of electricity used. So, assuming an electricity cost of 16p/kWh, such a system would cost 4p/kWh to run.

Add in the RHI savings that are available, and the savings increase even further.

In conclusion

The decision of whether a ground source heat pump is right for your budget or not is not straightforward, but it isn’t that complicated either. Just bear in mind the points above, be clear about your budget, the lifetime cost of the system (including both installation and running costs) and research the grant funding that is available through the RHI incentive scheme, which sadly is coming to an end at the end of March 2022.

With those facts in mind, a calculator and a cup of coffee, you’ll be able to reach the right decision for your particular circumstances.