The best way to pay for energy
28 Mar 2024
By clicking a retailer link you consent to third party cookies that track your onward journey. If you make a purchase, Which? will receive an affiliate commission which supports our mission to be the UK's consumer champion.
In this article
A ground source heat pump system harnesses natural heat from the ground.
A heat pump can heat your home efficiently, and reduce your carbon emissions. It can also heat water stored in a hot water cylinder.
If you're thinking of buying a heat pump, it will likely be an air source, rather than ground source heat pump. If you have a large garden, however, a ground source heat pump might be a good choice.
A ground source heat pump performs the same role as a boiler in a central heating system. But it uses ambient heat from the ground to generate heat, instead of needing to burn fuel.
While you still need to use electricity to power a heat pump (and therefore heat pumps aren't zero carbon) our electricity increasingly comes from renewable sources. Therefore heat pumps are much more environmentally-friendly than gas boilers.
Read on to find out more about how a ground source heat pump works and whether one would be right for your home and budget.
Heat pumps vs boilers: the key things you need to know
Ground source heat pump systems are made up of a ground loop, which is a network of water pipes buried underground, and a heat pump situated at ground level.
A mixture of water and anti-freeze is pumped around the ground loop and absorbs the naturally occurring heat stored in the ground.
The water mixture gets compressed and goes through a heat exchanger, which extracts the heat and transfers it to the heat pump. The heat is then transferred to your home heating system.
How big the ground loop needs to be depends on how big your home is and how much heat you require, but you'll need plenty of garden space either way. The Energy Savings Trust says, for a newbuild three-bedroom house, you could expect two trenches of 30-40 metres in length, but more space would be needed if your home is larger or an older property with poor insulation.
The ground loop area will need to avoid trees, as roots will cause problems when digging trenches.
Your garden will also need to be accessible for digging machinery entering from the road.
If you have less space, it may be possible to drill vertical boreholes to gather heat. This method can be more efficient (as the ground gets warmer the deeper you dig) but will also be more expensive. Bigger properties may need multiple boreholes.
If your garden is too small for a ground source heat pump, you could install an air-source heat pump instead. These are usually placed outside at the side or back of a property, and take heat from the air. For more details, see our guide to Air source heat pumps explained.
Inside your home you will need space for the indoor heat pump unit. This may contains the hot water cylinder or the cylinder may be separate.
A well set-up heat pump (ground source or air source) that is running properly shouldn't leave your home cold.
A ground source heat pump can increase the temperature from the ground to around 50°C. The hotter you heat your water, the more electricity you'll use.
You can then use this heat in a radiator, for hot water, or in an underfloor heating system. Whether you'll need an additional back-up heating system is dependent on your property. A well-insulated home can be adequately brought up to temperature with central heating running at 50°C, but you might find this insufficient if your home leaks a lot of heat. If your home is poorly insulated, it's advisable to improve your insulation regardless of whether you have a heat pump or a boiler, as you'll be paying to generate energy that is leaking back out.
Find out more about insulating your home including what to do and why this matters so much.
A ground source heat pump system can help to lower your carbon footprint as it uses a renewable, natural source of heat – the ground. According to the Energy Saving Trust, a heat pump with mid-range efficiency would save you most carbon when used to replace an old electric heating system (with storage heaters) or coal heating system.
Whether or not you get a heat pump, visit our energy comparison service to use our ratings and expert advice to help choose the right energy tariff for you.
While much more expensive to install, ground source heat pumps do typically have better efficiencies than air source heat pumps. While we expect a typical air source heat pump to be around 250% - 300% efficient, we would expect a typical ground source heat pump to be 350% - 400% efficient. But only your installer can give you a reliable estimate that's fit for your property.
Ground source heat pumps extract heat from soil which has a more constant temperature than the air, and the soil shouldn't go below 5°C in the year.
This also means that a ground source heat pump will have less efficiency variance throughout the year, while an air source heat pump may be very efficient on a mild day and more expensive to run during a cold snap.