Air Source Heat Pumps explained

Air Source Heat Pumps continue to grow as a viable, green alternative boiler that provides heating and hot water.
But how do they work, how much do they cost to run, and what are the advantages and disadvantages of this type of energy efficient system?

How do they work?

Air Source Heat Pump

ASHP’s capture the solar energy that has warmed the air and absorbs it, at a low temperature, into a fluid. Passing through a compressor, the temperature of the fluid is then increased. Finally, the higher temperature heat is then transferred to the heating and hot water circuits of the house. This all happens inside a unit which is mounted or installed on the floor around 300mm away from the external or in certain situations can be mounted directly on the external. They’re a bit bigger than a fridge, look like an air conditioning unit and generally come in two sizes (h)900 x (w)1300 x (d)320mm or (h)1400 x (w)1300 x (d)320mm.

Air-to-water heat pumps are one of the main types available and feeds heat into your wet central heating system. These work more efficiently at a lower temperature so a distribution system that delivers heat over a larger surface area is preferred. This means that they’re ideal for underfloor heating or radiators. Air-to-water heat pumps may also qualify for the governments Renewable Heat Incentive (RHI) which means you could get money towards renewable heating costs in your home over a 7-year period for domestic applicants or 20 years for non-domestic applicants.

ASHPs are suitable for any building, new build or retrofit.

Even when the outdoor temperature is as low as -15°c, ASHP’s continue to heat the home, producing around 2 kWh of heat energy for every 1 kWh of electricity. So, although the pump needs electricity to run, it should use less electrical energy than the heat it produces, making a difference to carbon emissions.

Air Source Heat Pump

How much do they cost to run?

As with any alternative energy system, the running costs depend entirely on how efficiently your system works. Running costs are determined by the size of your home, how old it is, how well insulated it is and how warm you want your house to be.

Other factors include the type of heating system you’re replacing, how you plan on using the heat generated by the ASHP, how long you have your heating on for.

If eligible for the RHI you could receive a payment every three months for the next 7/20 years. With this incentive, payments are based on the amount of renewable heat made by your heating system; estimates put domestic RHI payments between £600 and £1400 a year.

You could potentially save per year the following by replacing your existing system with an ASHP:

  • £560-650 from an old (G-rated) gas boiler
  • £930-1,100 from an old (G-rated) oil boiler
  • £1,065-1315 from old electric storage heaters
  • £1365-1610 from an old (G-rated) LPG boiler

Reference: Energy Saving Trust

With old and inefficient systems like these, an ASHP could work out cheaper and offer you the option of saving money. 

Air Source Heat Pump

What are the advantages and disadvantages? 

As with any renewable energy system, there are advantages and disadvantages. The successful use of an ASHP depends on a variety of factors, not least the efficiency of the building itself. It’s important to consider the individual situation; location, building size and specific requirements. ASHP’s require little maintenance, however they aren’t a flawless system.

Let’s look at the advantages:

  • RHI approved – you can qualify for this financial incentive that pays you for generating your own heat through renewable technology.
  • Lower fuel bills – especially if you’re replacing conventional electric heating or old systems as identified above.
  • Heat and water – you can heat your home as well as satisfy your hot water needs.
  • Easier install – ASHP’s are often easier to install than alternative systems such as Ground Source Heat pumps, partly due to the small area needed.
  • Lower carbon emissions – depending on the fuel you’re replacing, you can significantly reduce your carbon footprint.
  • Low maintenance – you can expect them to operate for 20 years or more, however they do require an annual service.
  • Be in control – With Wi-Fi enabled room-stats/controls you can connect your smart phone to your heating system and control the day to day running.


  • Semi-renewable – as the unit uses some electricity to run the pump, it means it isn’t completely carbon neutral, even though it uses electricity more efficiently than regular electric heating units
  • Planning – if the installation doesn’t fall under permitted development, then you may need to get planning permission for the installation. This is something we can help with at a quotation stage
  • Lower heat – they provide a lower heat than conventional systems so it’s important to ensure an in-depth survey is carried out.
  • Space – as ASHP’s need outdoor space for the unit, they aren’t suitable for flat or apartment living.

Air Source Heat Pumps are becoming increasingly popular and have caught the attention of more and more homeowners in recent years. Not only because it is using technology as a viable alternative boiler but also because of the Renewable Heat Incentive that is available.  As with any system, it is essential to design and specify requirements of the property, so the install and ongoing usage is optimised.

Visit our website for more information on Domestic or Commercial installations. For any queries about Air Source Heat Pumps, give us a call on 01522 803 854 or email us at