Heat Pumps use the free heat energy from the earth, water or air and draw it into the building to provide space heating and, in some cases, to pre-heat hot water. They can also be used to cool the house in summer. They work like a fridge – liquid in looped pipes extracts heat from the earth, water or air, and draws it into your house to heat it via radiators or under-floor heating. They need electricity to pump the heat, but for every unit of electricity used, 3-4 units of heat are produced.
Ground source heat pumps are most efficient because the temperature under ground remains more or less constant all year round.
What are the costs and savings?
Heat pumps cost between £800 and £1400 per 1kilowatt of heat output. So a typical 8 kw system will be £6,400-£9,600 plus the price of the internal pipework and radiators or underfloor emitters (if necessary). The Energy Saving Trust gives more details on costs and benefits.
Important points
- Heat pumps can be installed in existing houses, even without much space outside. However, if there is not much outside space the loop must go deep into the ground rather than horizontally, or an air source heat pump may be more suitable.
- The ground will need to be suitable for digging a trench or borehole.
- The existing central heating pipes and radiators can be used to circulate the heat, but under-floor heating is better as it works more efficiently at a lower temperature.
- Solar or wind power may be used to generate the electricity needed for the pump. If not, choose the best electric tariff for lowest running costs, for example economy 7.
- An accredited installer will be able to provide more detailed advice.
- Heat pumps are a good option where gas is not available
- If you are building a new house or extension or other major building works requiring excavation equipment, this can make the installation of a heat pump more cost-effective.
- Make sure your property is well insulated to lower your need for space heating and make the system more effective.