Benefits
- Low carbon heat source
- Potentially low running costs
What it is
A ground source heat pump is a low carbon heating system and works differently to a boiler. Rather than burning a fuel like gas or oil, it uses electricity to transfer heat from one place to another. In this case, from the ground to your home to provide space heating and hot water.
Left to its own devices, heat will normally flow from a hot place to anywhere that is colder. A heat pump is an appliance that makes heat flow in the opposite direction – it “pumps” the heat from a cold place to somewhere that is warmer.
A ground source heat pump takes heat from the ground and transfers it to a working fluid. It does this either through a horizontal loop of pipework buried beneath the ground (a ground loop) or from holes drilled vertically into the ground (a borehole). The heat pump then uses a compressor to change the pressure and temperature of the fluid until it is warm enough to provide heating for the house.
The heat pump uses electricity, so it is not free to use and it is not yet zero carbon. But provided that the heat pump is properly installed in a suitable building, it will produce more energy as heat than it uses as electricity. If it runs efficiently it can be cheap to use and will be a low carbon heating option for your home.
Heat pumps are more efficient when they give out heat at a relatively low temperature. They are often used with underfloor heating, as this can operate successfully at low temperatures, but they can be used with conventional radiators.
Is it right for me?
Ground source heat pumps require either a large garden or similar area for a ground loop, or a smaller area with access for drilling equipment, for a borehole. They are most likely to be attractive in homes that are well insulated, and where other heating options like gas are not available.
Heat pumps are more efficient when they do not have to raise the temperature of the heat they extract too much. This means they are more efficient when they can run a heating circuit at a lower temperature. If your home is well-insulated then it needs less heat to keep it warm. Where possible, it is recommended that you have a minimum level of insulation in your home, such as loft and cavity wall insulation, before you consider installing a heat pump. You can run your radiators or underfloor heating at a lower temperature and still keep your home at the temperature you want.
If you live in a fairly new house, or if you already have underfloor heating, then you could be well suited to a heat pump. If not, you may want to look at increasing your insulation levels or changing your radiators.
If your house is suited to a heat pump but you do not have space for a ground loop or borehole, then you might want to consider an air source heat pump instead.
Using it
A heat pump can keep your home comfortable and your water hot, while keeping your bills and your carbon emissions down, but you will need to use the system in the recommended way to make the most of these benefits.
If you have gas central heating, then you probably set it to come on about half an hour before you get up in the morning. The boiler will run at full blast for that half an hour to make sure your home is warm when you get out of bed. This works well because a gas boiler can provide a lot of heat very quickly.
Heat pumps are at their most efficient when running steadily and producing heat at low temperature. To make the most of your heat pump you may need to programme it so that it can run for longer than a gas boiler, but at lower output. This may mean you leave the heating on for periods when you would turn it off if you had gas heating. So, for example, it may take longer to heat up your home from cold than with a boiler.
Your installer will advise you on how to set your heating controls. You should follow this advice to avoid getting unnecessarily high heating bills.