A Brief Guide to air source heat pumps

We currently have funding available to support the installation of an air source heat pump in your home. To find out more and to apply, click here

1.    What is an Air Source Heat Pump?

A heat pump is used to provide heating and hot water for your home and would replace your typical gas boiler. Heat pumps take the heat from outside and use this to heat water for use in your home. Heat pumps can take the heat from the outside air, the ground or less commonly, the water.

Air Source Heat Pumps (ASHP)

A heat pump operates like an air conditioning unit, but in reverse. They use a heat source (the air, water or the ground) to heat a refrigerant, and then transfers that heat from the refrigerant to a hot water tank in your home.

Whereas a gas boiler will heat water to about 75oC, a heat pump delivers water at a much lower temperature of around 35oC – 45oC, which is still hot enough to heat your home, but also much more efficient. For this reason, heat pumps work best with underfloor heating, but radiators can still be used, although they need to be larger than those used for a gas heating system.

Other Types of Heat Pump

Due to more consistent temperatures below ground and in water, Ground Source Heat Pumps (GSHP) and Water Source Heat Pumps (WSHP) are even more efficient than ASHPs, but generally more expensive to install because of the work involved in installing the ground or water pipework.


2.    Benefits

Financial savings

Heat pumps are powered by electricity, so they are not free to run, but they’re far more efficient than other electric heating systems. An ASHP will convert every 1 unit of electricity it consumes into around 3 units of heat, making them 300% efficient. This makes them a much cheaper heating system to run than standard electric heaters or night storage heaters.

Carbon savings

Using a heat pump means that your carbon emissions will be about 70% lower than those with direct electric panel or storage heaters. Furthermore, if you have switched to a 100% renewable electricity tariff, the carbon emissions of your heat pump are effectively zero.

Compared to those using a gas heating system, your emissions would be about 60% lower. Changing your system from gas to an ASHP will also improve local air quality.


3.    Property Suitability

Heat pumps work best in draught-proofed properties that have good levels of insulation. If your home is old and not well insulated, you may want to consider insulating it, prior to installing the heat pump.

They work best with underfloor heating, but they can also work well with radiators. However, the radiators for a heat pump are usually larger than those used with a conventional gas boiler, so you may have to upgrade your radiators when swapping a gas boiler for a heat pump.


4.    Different ways to set up your system

The typical way to set up a heat pump system is to simply have a heat pump and hot water tank (thermal store). The water tank will also have an immersion heater, which is an electric heating element inside tank which can heat the water (like a big kettle) if the heat pump is not operating or needs a boost.

You will need to decide whether you will use underfloor heating, radiators or a combination of the two.

Solar panels can also be a good way to provide free electricity for your heat pump and immersion heater; particularly when coupled with a battery.


5.    Typical Costs

The cost of your system will vary depending on several factors: the size of heat pump needed, the type of system (air, ground, water), whether you need new emitters (underfloor heating and/or radiators) etc.

The Energy Savings Trust estimates a typical ASHP installation will cost in the region of £14,000. Partial funding is available through the the Boiler Upgrade Scheme, or you may be eligible for full/partial funding through the Warmer Homes or ECO 4 schemes. Contact the team today to see whether you might be eligible.


6.   Payback Period and Return on Investment

If you are replacing expensive heating systems like direct electric heaters, an ASHP could be a good choice. The savings from an ASHP should offset the capital cost over its lifetime. If you are replacing gas central heating, which is relatively cheap to run, the apparent payback may be less.


7.    Installation

Heat Pumps are relatively easy to install, especially if you’re building a new property or refurbishing an existing one. Space is required for the hot water tank (thermal store) and the heat pump, plus the external air handling unit.

Things you may want to look for:

  • Accreditation: any funding scheme (current or future) will typically require you to use an accredited installer to access the funding so it is work considering this. Installers should be TrustMark and/or MCS accredited.
  • Who will be doing the work? Many installers create sub-contract jobs and you should ask if they will do this and if so, to who?
  • Reviews or case studies: If they are reputable (third party reviews or case studies)


8.    Accreditation

MCS certification:

This covers low-carbon heating installer and confirms the install is completed by a certified installer who has passed the quality and technical standards. You can read more on MCS here.


This covers a broad range of home upgrades including homes insulation and heat pump installations. You can read more on TrustMark here.

9.    Maintenance

Heat pumps are relatively low maintenance but will require annual servicing, as would a gas boiler. You can expect an ASHP to last for around 15 to 20 years, which is longer than a gas boiler.