Ground-source heat pumps extract latent heat from the ground via a borehole or a network of underground pipes. This heat is then converted through the heat pump into thermal energy for heating and hot water.
It is not technically renewable energy, as electricity is needed to power the pump, although this amounts to a third of the energy produced so the excess could be termed renewable (you could power the pump using another form of renewable energy such as solar).
Heat pumps are most suitable to new-builds where they can be immersed underneath the
building, or existing properties with garden space.They don't work well with existing radiators as the temperature they generate - 50C -is far too low. Instead, team them with underfloor heating, which uses radiant heat at a lower temperature to heat the fabric of the building, rather than the air within.
Systems are easy to maintain, last at least 20 years and cost between £6,500-£12,000. Grants are available from the Low Carbon Buildings Programme. For more information contact The Ground-Source Heat Pump Association (01908 665555: www.nef.org.uk/gshp).