Heat Pumps

Heat pumps use similar technology to fridges to extract heat from the air, ground or water to provide space and water heating. They can also provide cooling by running in reverse to extract heat from the building when it is hot.

The Technology

Heat pumps require electricity to run and the CO2 and financial cost of this electricity needs to be taken into account. A heat pump’s coefficient of performance (CoP) is the measure of how many units of heat you get out for each unit of electricity you put in. The higher the CoP, the more efficient the heat pump is running and the higher the CO2 savings and the lower the running costs.

Heat pumps provide a low temperature heat output and are therefore best suited to meeting a low heat demand e.g. well insulated properties with underfloor heating, rather than a conventional central heating system which requires a much higher temperature output. If the heat pump is providing water heating, it is best to use the heat pump to pre-heat the water and then use another heat source to get the water to the necessary temperature, rather than run the heat pump inefficiently.

Considerations

Ground source heat pumps (GSHPs) require either horizontal trenches or vertical boreholes to be dug. Boreholes need to be between 50 metres and 100 metres in depth and are more expensive, sometimes requiring a drilling licence. Sufficient space is needed for horizontal trenches, which need to be around 1.5 metres to 2 metres deep and 40 metres to 100 metres long.

Air source heat pumps (ASHPs) and water source heat pumps (WSHPs) require less space than GSHPs but have lower CoPs. Noise may be an issue for ASHPs. WSHPs may require approval from the Environment Agency and need to be sunk in a body of water that doesn’t freeze in the winter.

Operation and Maintenance

There is virtually no maintenance required for heat pumps. Pressure in the pipes may need to be monitored.