Air source heat pumps

Air-to-water heat pumps absorb heat from the outside air and transfer the heat to water.

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. This makes them more suitable for underfloor heating systems or larger radiators, which give out heat at lower temperatures over longer periods of time.

Air-to-water heat pumps are the most common model in the UK.

Air-to-air heat pumps require a warm air circulation system to move the warm air around your home. They will not provide you with hot water as well. Air-to-air heat pumps are not eligible for the UK Government’s Renewable Heat Incentive (RHI) scheme.

You’ll need a place outside your home where a unit can be fitted to a wall or placed on the ground. It will need plenty of space around it to get a good flow of air.  The external unit is connected to an internal unit containing circulation pumps and hot water, which is usually smaller than the average boiler.

As a general rule, air source heat pumps are easier to install than ground source heat pumps, as they do not require any land to be dug up for installation. The size of the air source heat pump will vary depending on your home’s heat demand – the bigger the home, the bigger the heat pump unit you’ll need.

Air source heat pumps perform particularly well with underfloor heating systems or warm air heating because they operate at low temperatures. Homes without an existing central heating system will require one to be installed for an air source heat pump to work.

An air source heat pump is subject to fluctuating air temperatures and has to work harder to produce heat when the outside air temperature is lower. This means that in the colder months, when the heat pump is likely to be relied on the most, it will use more units of electricity to produce the same amount of heating as a ground source heat pump in the same period of time.

Since air source heat pumps work best when producing heat at a lower temperature than traditional boilers, it’s important that your home is well insulated and draught-proofed to minimise heat loss.

Air source heat pumps will continue to operate at temperatures of around -15°C (some can operate at even lower temperatures), but will be most efficient at higher temperatures.

The system is more likely to pay for itself if it’s replacing an expensive system like electric heating. You’re unlikely to save much on your heating bill if you’re switching from mains gas.

Installing a typical system costs around £9,000 to £11,000. Running costs will vary depending on a number of factors including the size of your home, how well insulated it is and what room temperatures you are aiming to achieve.

While air source heat pumps don’t take up too much outdoor space, the unit will be visible from the outside of your property, so it’s best to check with your local planning authority first, to find out if you need planning permission. As the unit is above ground, it will produce a noise similar to that of an air conditioning unit, which could be bothersome to you or your neighbours.

Find out more about getting permission for the siting and external appearance of an air source heat pump.