Air source heat pump’s (ASHP) are usually placed outside at the side or back of a property, and take heat from the air and boosts it to a higher temperature using a heat pump. This heat is then used to heat radiators, underfloor heating systems or even warm air convectors and hot water in your home.
The pump needs electricity to run, but the idea is that it uses less electrical energy than the heat it produces.
Ground source heat pumps are also available. They draw heat from the ground via a network of water pipes buried underground, usually in your garden. See our separate guide to ground source heat pumps for more details.
ASHPs are cheaper than ground source heat pumps. The Energy Saving Trust (EST) estimates that the cost of installing a typical ASHP system into a detached home ranges between £6,000 and £10,000.
The payback period (the time it takes for the cost of the system to be recouped in energy savings) depends on how efficiently your system works, the type of system you’re replacing, whether you can get money with the RHI and how you’ll be using the heat generated from the pump.
The EST says that an average performing air source heat pump could save between £150 (replacing oil) and £530 (replacing electric heating) a year. The government has estimated that the RHI would pay an extra £500 a year.
Here are some general rules of thumb to bear in mind:
Like ground source heat pumps, air-to-water ASHPs work better with underfloor heating systems. If underfloor heating is not possible, large radiators should be used. This is because the heat generated by the heat pump is not as high as that produced by a conventional boiler, so a larger surface area is needed to achieve similar temperatures in your home.
Air-to-water heat pumps could be better suited to new-build properties than retrofit - this is because costs could be reduced if the heat pump is included as part of the building specification, rather than having to retrofit underfloor heating later on.
Heat pumps can save you more on your heating bills if you're replacing an electric, LPG or coal system, rather than gas.
A well-insulated house is essential to best optimise the heat generated by your ASHP - otherwise the heat the pump is generating escapes more easily.
Once in place, the heat pump should require little maintenance.
Heat pumps qualify for the Renewable Heat Incentive (RHI) Premium Payment (a one-off grant of £1,300) until 31 March 2014, and will be eligible for the full RHI in spring 2014.