Air Source Heat Pumps project guide

What is it?

Air Source Heat Pumps (ASHPs) use heat from the air outside to heat your home or hot water system. Designed well, an Air Source Heat Pump will provide all the hot water and heating a property requires for 365 days a year.

What is it suitable for?

Air Source Heat Pumps are compact and externally situated so are suitable for a wide range of properties.

Working at a lower temperature than oil or gas boilers, Air Source Heat Pumps are recommended for well-insulated properties.

They are well-suited to new build properties, in particular those that do not have a gas supply, because the running cost comparisons versus oil boilers are particularly attractive.

They are popular with developers building new build homes as they integrate well with underfloor heating.

They work well in existing buildings that are well-insulated, but make sure an experienced installer checks whether your existing radiators are big enough to heat your home. It is quite common for an existing property that is refitted with an air source heat pump to have underfloor heating fitted downstairs, whilst existing radiators are retained upstairs.


  • They can provide you with an income through the Renewable's Heat Incentive (RHI)

  • They do not need planning permission from your local council

  • Save up to 30% on energy bills

  • Can provide lower home carbon emissions (depends on the fuel you are replacing)

  • No fuel deliveries needed

  • Provides heating and hot water

  • Required minimal maintenance

  • Lower cost installation versus Ground Source Heat Pumps

How does it work?

Heat Pumps use refrigeration technology to provide heat from a condensing unit.

Heat Pumps use refrigeration technology to provide heat from a condensing unit. Each unit contains an evaporator which absorbs energy from the air outside the house and transfers it to the heating system via a heat pump - this process uses the principles of vapour compression.

Heat Pumps require electricity to run so they work well with electricity-generating Solar Panels.

The efficiency of a heat pump is denoted by its coefficient of performance know as ‘COP’. This is the ratio of energy extracted from the source and energy used by the heat pump itself. Typical COP values for ground source heat pumps are 3.5-4.5, whereas air source heat pumps tend to have a CoP of between 2.5-3.5. With the current mix of fuels for electricity production, using a heat pump produces slightly less emissions compared with conventional gas heating.

How does it compare?

Find out how ASHPs compare against Ground Source Heat Pumps

Ground Source Heat Pumps:

  • Higher installation costs

  • Ground Source are more efficient - due to constant temperature underground

  • Require a large outside area for loops

  • Efficiency dependent upon soil and rock type

  • Qualify for RHI payments

  • Do not require planning permission

  • Low maintenance

Air Source Heat Pumps:

  • Lower installation costs

  • Air Source are less efficient than Ground Source

  • Require a compact outside area

  • Efficiency is not linked to soil and rock type

  • Qualify for RHI payments

  • Do not require planning permission

  • Low maintenance



  • A typical Air Source Heat Pump will cost around £7,000 to £11,000 fully installed, dependent upon the model chosen, and the size of the building.

  • For some Retrofit projects you may also choose to budget for an Underfloor Heating system, which will be more efficient than radiators as they can be run at a lower water temperature


  • Independent figures from the Energy Saving Trust suggest in standard 4-bedroom house you should be able to save between £295 per year compared to an older Gas Boiler and £1,000 for electric storage heaters.

  • In addition, you should be able to earn between £900 and £1,300 per year through the Renewable Heat Incentive.