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Air Source Heat Pump: Is it right for your home?

Posted by Faisal Hussain (HIES Scheme) on 24 January 2018 at 9:30 am

Much of the UK has been feeling the cold during these past few months which means many of us are now leaving our heating on for longer periods of time, which of course is going to hit our pockets. So, the question is how can we keep our homes warm without significantly increasing our energy bills. Well there could be a way, by installing an air source heat pump (ASHP) - an alternative to traditional heating mechanisms like gas fired boilers, electric storage heaters etc.

An ASHP could be used to heat your home and as well as water if you have a hot water cylinder. There are two main types of ASHPs:

-    Air to water, which takes heat from the outside air and feeds it into a wet central heating system.

-    Air to air, which takes heat from the outside air and feeds it into your home through fans.

The question is how can you determine if its right for you as purchasing an ASHP is a considerable investment. To help you decide, we have provided you with five key factors to consider for an air to water ASHP which is only providing heating:


1. Initial investment

The purchase of an ASHP is significant compared to purchasing a gas boiler. The size of the ASHP required for your home depends on a range of factors, including the heat loss of your home. The greater the heat loss of your home the bigger the ASHP required, which could impact on the price. From research carried out by HIES Consumer Code, the average contract value for an ASHP is approximately £12,000. Its therefore, vitally important to understand the motivation behind the purchase, to ensure you are satisfied.


2. Domestic renewable heat incentive

The domestic Renewable Heat Incentive (RHI) was launched on 9th April 2014 and is a UK Government scheme, set up to encourage uptake of renewable heat technologies amongst householders through financial incentives. If you join the scheme with an ASHP and keep to its rules you will receive payments every three months for seven years. The RHI amount you could receive on a quarterly or yearly basis depends on a number of variables. You can obtain an estimate by using the government’s Domestic RHI calculator and following the instructions. If you have an Energy Performance Certificate (EPC) for your home dated after July 2012 then this will show ‘Your home’s heat demand’ (normally on the second page), which will allow you to obtain your RHI estimate, using the calculator. The greater your heat demand figures on the EPC the higher the RHI payments you could receive. A house with an EPC space heat demand requirement of 15,000 kilowatt hours per year (kWh/year) could receive around £1,000 per year. For further information please read Ofgem’s Domestic Renewable Heat Incentive essential guide for applicants.


3. Running cost of ASHP

To calculate an estimated running cost of an ASHP, you will need to know how efficient the ASHP is at generating heat. Most ASHPs should work on a Seasonal Performance Factor (SPF) of 3. This means that for every 1 kilowatt (kW) of electricity the ASHP uses, it generates 3 kW of heat. Therefore, where the house space heat demand requirement is 15,000 kWh/year, the amount of electricity needed to run the ASHP would be 5,000 kWh/year (15,000 ÷ 3). If your unit rate of electricity is 12p the total estimate running cost for the ASHP would be £600 per year (5,000 × 12p). As the ASHP is run on electricity there may be an opportunity to find a better unit rate of electricity, by shopping around or using Energy Savings comparison websites and finding a better deal. The lower your unit rate of electricity the cheaper it will be to run an ASHP.


4. Projected Energy savings

The amount of money you will save on your energy bills in a year from changing to an ASHP will depend upon the type of heating system you are replacing and how old that system is. Typically, you will experience greater savings in energy if it's replacing an electric or coal heating system. However, if you are replacing a relatively new heating system (eg an A rated gas boiler) then it could work out more expensive to run an ASHP. To show this, if you were replacing a gas boiler that was less than 10 years old then based on 15,000 kWh/year heat demand it would cost around £550 per year to heat your home using your existing gas boiler (based on the efficiency of your current gas boiler running at 82% and your gas unit rate of 3p). If you compare this to the running cost of ASHP of £600, based on the illustration in point 3, you could be paying around £50 more per year with the installation of an ASHP. If you have taken into consideration making energy savings every year to assist in paying for the ASHP then you will need to ensure the energy savings are realistic and can be realised.   


5. Suitability of your home

During your decision-making process you should also consider the practicalities behind the installation of an ASHP. You will need an area outside of your house to install the unit, either on the ground or fitted on a wall, and it will need plenty of space around it for a good flow of air to reach the ASHP. Its also important that your home is well insulated for you to gain the most efficiency out of the ASHP. Ofgem stipulate that if your EPC recommends you need to install loft or cavity wall insulation, then you must do this before you can claim RHI. As the ASHP produces heat at lower temperatures than a conventional boiler, it will work better with underfloor heating because a larger surface area is needed to achieve similar temperatures in your home. If you have radiators, then you will most likely need to replace these with larger radiators, in order to provide sufficient heat. This is very important because if your radiators are too small in size and specification then it will be difficult for them to produce enough heat when connected to an ASHP.


Whether an ASHP is right for you will depend on your reasons and motivation behind considering it. To help you make an informed decision its always sensible to receive several quotations allowing you to compare any RHI figures, running costs and projected energy savings. The figures within the quotations should be within a 10% tolerance limit of each other and if you are unsure of anything or have a question always ask the installer or an independent body.  



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About the author:

The Home Insulation & Energy Systems Contractors Scheme (HIES) is a Chartered Trading Standards Institute approved Consumer Code for the renewable sector. The HIES Code of Practice requires that consumers are dealt with professionally, courteously and sympathetically.  Any products installed by HIES members must be fit for purpose, installed professionally and come with comprehensive guarantees which are covered by specialist insurance, providing consumers with a high level of protection and peace of mind. We aspire to deliver world class dispute resolution services and provide consumers with free access to our frontline complaints team, mediation, independent inspections (at our discretion) and free access to an independent ombudsman. For further information about HIES visit or follow us on Twitter or Linkedin.

If you have a question about anything in the above blog, please ask it in the comments section below.

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6 comments - read them below or add one


homefarmComment left on: 20 February 2020 at 11:04 pm

Please check out our honest verdict on the efficiency, effectiveness and sustainability of air source pumps in the UK.

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homefarmComment left on: 20 February 2020 at 11:01 pm

Not heard of them Pool. How did you come along?

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poolpoolpoolComment left on: 2 December 2019 at 4:33 pm

I hav e had a ASHP installed and they fitted a LG unit , it faulted after one month and the installers are now fitting a Grant unit which thery say are better, can anyone help me with believing this or are they saying this to fit a cheaper unit?

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homefarmComment left on: 17 July 2019 at 9:51 pm

We installed Global Energy Systems’ Caernarfon 18kW Eco Air Source Heat Pump.


You can read about our system here:


Or, watch our overview video on YouTube:

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Oaklands End

Oaklands EndComment left on: 3 December 2018 at 9:48 am

Good article.  I've had an ASHP for 4 years now and I am very pleased with its performance and running cost - it replaced an oil system and I reckon my oil costs fell by about £100 pm, whilst electricity costs increased by about £50 pm.  The 7-year grant was a big incentive, though the installer wrongly extimated the entitlement by calculating on the whole energy output, without deducting the input.  This turned out to be an error with the Samsung spreadsheet they were using (system supplied is Panasonic).  So, my payment is 37% lower than originally quoted.

I disagree with the comment about needing to replace radiators.  I havent had to.  I did make sure an extension we had on the house had double radiators and was well insulated (150mm insulation board throughout, including under the floor).  The extension has reduced the heat loss of the house, being on the north east side.

My other comment is you do have to think about the noise of the ASHP.  We do not have a neighbouring property on the side of the house where it is situated.

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dominator99Comment left on: 31 January 2018 at 12:20 pm

I run an ASHP which provides HW all year round & supplements conventional Gas CH & HW.

I also have a 3.9kW solar panel array & on a sunny summer's day provided more than enough power to run my ASHP further reducing my electricity bill. Even during winter the solar PV reduces the electricity consumption of the ASHP

My gas boiler is turned off from approx April to October so the ASHP provides all my HW and additional HW heating is provided by an electronic solar diverter which heats 3 domestic HW cylinders

My home has cavity wall insulation & 4" underfloor & 'warm room' loft insulation (insulation between rafters rather than ceiling joists).

Insulation is critically important if your considering an ASHP

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