An Air Source Heat Pump is located outdoors at the side or back of the property. It draws heat from the air and boosts it to a higher temperature using a heat pump. The pump needs electricity to run, however it will use less electrical energy than the heat it produces, and this is referred to as the Coefficient of Performance (CoP) the higher the CoP the more efficient the heat pump, this varies throughout the year (seasonal fluctuations) to reflect this air source heat pumps are rated with a Seasonal Performance Factor (SPF).

The SPF represents the total useful heat that has been generated annually from the ASHP and then divided by the annual electricity consumption. So if the SPF is 3, the system is expected to give 3 units of heat energy for each one used. To be eligible for the Boiler Upgrade Scheme [BUS] Clean Heat Grant a minimum SPF of 2.8 must be achieved.

Heat from the air is absorbed at low temperature into a fluid. This fluid then passes through a compressor where its temperature is increased, and transfers its higher temperature heat to the heating and hot water circuits of the house.

Air Source Heat Pumps allow you to use renewable heat for your heating systems and hot water in your home. Heat pumps are compatible with a variety of heating systems, including radiators, underfloor heating or warm air convectors.

Unlike gas and oil boilers, heat pumps deliver heat at a lower temperature over longer periods, to keep your rooms at their ideal environment throughout the day and night.

The benefits of air source heat pumps:

• Lower fuel bills, especially if you are replacing conventional oil, LPG or electric heating
• Receive a grant through the UK government’s Boiler Upgrade Grant
• Lower home carbon emissions, depending on which fuel you are replacing
• No fuel deliveries needed
• Can heat your home as well as your domestic water
• Minimal maintenance required
• Easier to install than a ground source heat pump.

• Must be replacing a fossil fuel boiler of any kind or direct electric heating system (such as storage heaters, electric panel radiators or an electric boiler).
• Custom new builds are eligible and do not require an EPC.
• If you are in a listed property or conservation area the same exemptions apply as they did for the RHI approval criteria
• Must be a MCS accredited heat pump.
• The ASHP must have a minimum efficiency in the home of 2.8 SCOP Exclusions
• Hybrid systems - comprising a gas or oil boiler and heat pump - are not eligible.
• ‘Heat-only’ systems where the heat pump only provides space heating and hot water is supplied by a fossil fuel boiler. Immersions for topping up the hot water and for anti-legionella protection are permitted. Solar thermal is also permitted as long as the heat pump is set up to meet the full space and water heating demand.