How do air source heat pumps work?

An air source heat pump extracts heat from the outside air in the same way that a fridge extracts heat from its inside. It can extract heat from the air even when the outside temperature is as low as minus 25° C.

Heat pumps have some impact on the environment as they need electricity to run, but the heat they extract from the ground, air, or water is constantly being renewed naturally.

Unlike gas or oil boilers, heat pumps deliver heat at lower temperatures over much longer periods. This means that during the winter they may need to be left on 24/7 to heat your home efficiently. It also means that radiators should never feel as hot to the touch as they would do when using a gas or oil boiler.

There are two main types of air source heat pump system:

• An air-to-water system distributes heat via your wet central heating system. Heat pumps work much more efficiently at a lower temperature than a standard boiler system would. So they are more suitable for underfloor heating systems or larger radiators, which give out heat at lower temperatures over longer periods of time.
• An air-to-air system produces warm air which is circulated by fans to heat your home. They are unlikely to provide you with hot water as well.

Heat from the air is absorbed into a fluid which is pumped through a heat exchanger in the heat pump. Low grade heat is then extracted by the refrigeration system and, after passing through the heat pump compressor, is concentrated into a higher temperature useful heat capable of heating water for the heating and hot water circuits of the house.

The benefits of air source heat pumps

• Can lower fuel bills, especially if you are using conventional electric heating.
• Can reduce your carbon footprint: heat pumps can lower your home’s carbon emissions, depending on which fuel you are replacing.
• No fuel deliveries required.
• Can provide space heating and hot water
• It’s often classed as a ‘fit and forget’ technology because it needs little maintenance.
• Can be easier to install than a ground source heat pump, but efficiencies can be lower.