Air Source Heat Pumps

Air Source Heat Pump (ASHP)

With the Governments’ announcement of £5,000 grants towards the cost of Air Source Heat Pumps (ASHP) installation, we thought our customers would be interested to have some more information about the ASHP technology.

An ASHP is, effectively, a fridge in reverse. It extracts heat from the outside air and using a compressor turns this into useable heat which can warm your home and your hot water.

There are many manufacturers of ASHP’s and correspondingly a range of prices.

In the BBC’s report on the Government’s announcement, it is suggested that the cost of installation ranges from £6,000 – £18,000.  Given the cost of equipment and labour of an install, we would respectfully comment that the lower figure is unlikely. However, the upper figure is reasonable, depending on a number of factors which we highlight below.

Currently the Government offers a Renewable Heat Incentive (RHI), details of which are below.

At this stage we believe both the RHI and the Grant are available however this needs to be confirmed by the Government.

We also understand the £5,000 grant comes from a £450M fund which has to last 3 years and hence the Grant will be available to 30,000 homes per year. We estimate approx. 1.5M boilers are changed every year and so unfortunately this scheme may only cover 1 in 50 boiler changes. We have no information on the criteria for acceptance to this scheme or if any prioritisation will be given but it will mean that 49 out of 50 homes will not get the Grant.

Things to Consider:

  1. It is possible an ASHP may not be able to deliver the heat you need to keep warm in the middle of winter as they typically have a maximum possible output of 18KW (see below).
  2. Do you have Under Floor Heating (UFH)?  ASHP’s produce heating water at 45-55C which is what UFH systems are designed to run at and so work well together. Radiators are sized per room and typically expect hot water to be delivered between 65-70C and therefore it may be the case that in order to keep the room at a temperature you are used to in the middle of Winter, more or larger radiators may be required. There are similar checks required for the pipework running to the radiators, for instance microbore pipework is likely to cause issues and may need replacing.
  3. Is the primary drive for an ASHP to save money?  Natural Gas is the lowest cost energy per KW (currently between 2.5p and 3.5p per KW), followed by Oil and LPG with Electricity being typically the highest (currently between 12p and 14p per KW) and so over the course of an entire year it is likely your heating costs with an ASHP will be the same or possibly higher than the equivalent Gas boiler.  
  4. The local Electricity provider (DNO) will want to check the property in question will not exceed their thresholds once an ASHP is installed. This often necessitates a “load check” and may result in some electrical work being required.
  5. If you have a combination Gas boiler and do not have a hot water cylinder, an ASHP installation will need to include a cylinder to store your domestic hot water, adding to the cost.
  6. There are planning considerations which need to be met.

Will an Air Source Heat Pump Work for Me?

The main question is what the heat loss for your home is. A heat loss calculation (HLC) works out how much heat your home will lose and this dictates the heat you need to put in to keep the property at a constant temperature.  An accurate HLC will need the U values of walls/windows/roof as part of the calculation.  If the HLC shows your property loses an amount of heat greater than an ASHP output and insulation will not resolve the issue then an ASHP is not for you.

For many properties the answer is insulate insulate insulate!

Insulation will keep more heat in and keep the property cooler in summer too, many measures can be done by the homeowner and give an instant benefit, this is probably the best thing that homeowners can do to help the environment and save money in the short term.

For some properties, such as very large properties, or listed properties, insulation will either not be possible or will still allow more heat to escape than an ASHP can provide.  If an ASHP is still desired, then a bivalent system is possible where an ASHP is used in milder conditions and a “peak load” boiler is used for very cold conditions. This mix and match approach works well but it is not 100% green, it does not attract the full RHI, is much more expensive and we have no details as to whether it affects the recent grant.

If the HLC shows that an ASHP can provide enough heat, then the next step will be to assess the radiators and pipework as mentioned above. If the radiators and/or pipework needs upgrading, this is achievable but will add cost to the installation.

Renewal Heat Incentive (RHI)

The RHI currently pays every 3 months (in arrears) for a total of 7 years to the homeowner.

There is an upper limit on payment, for ASHP this is 20,000 KWh per year. Payments are made up to this limit. The payments (tariffs) change year by year and can be found on the Ofgem website.

There are some prerequisites required such as:

  • An accurate (within last 2 years) EPC. The EPC must meet minimum efficiency standards. If not, either apply for exemption approval or resolve the issue and re-do the EPC.
  • An MCS certificate must be available to apply for RHI.  
  • A Metering and Monitoring Service Package (MMSP) to be eligible (due to 2018 changes by BEIS).
  • The ASHP must provide space heating as a minimum. However, domestic hot water also allowed but only in conjunction with the former.
  • Swimming pools work well with an ASHP but are ineligible for the RHI.

The request for RHI must be made by the homeowner (or landlord) and not by 3rd parties.

There is an annual confirmation of compliance the homeowner is required to confirm. To include good working order and no material changes to the system.

Please note the above is based on the information available at the time of publishing.  Dated 21-10-2021.