In the second of the series of blog posts regarding technologies for retrofitting homes to be more sustainable, PJH are looking at air source heat pumps. Beginning with an introduction and facts regarding air source heat pump retrofit, including pros and cons, costs for an average home, potential payback timeframes and the required space for the system.
Air Source Heat Pump Retrofit Introduction
According to research by EDF Energy (2023) 95% of homes are centrally heated with a vast majority relying on gas or oil-fired boilers.
The UK Government has set out the goal to become net zero by 2050. Part of this involves a gas boiler ban as early as 2025 for new build properties. Existing gas supplied heating systems will be unaffected, but as fossil fuel prices become increasingly higher it’s ever more pertinent to explore alternatives, with assistance through the boiler upgrade scheme available.
It’s not always achievable to address all the sustainability issues of a dwelling in one go. Creating a retrofit plan for renovations and upgrades towards an end goal will help reach the desired level of integrating ‘green’ energy saving technologies into your home.
Air Source Heat Pumps (ASHP) are available in different formats for heating a dwelling. The two main ASHP’s are ‘air to air’ and ‘air to water’.
‘Air to air heat’ pumps take heat from the outside air and transfers it directly into your home via a ducting system to heat a room/space.
‘Air to water’ heat pumps take the heat from the air outside and transfers it to a dwelling’s heating system, for example; underfloor heating, central heating and/or hot water heating.
The unit which extracts the heat from the external air can be utilised within an existing system with minor modifications and is typically about as loud as a fridge. This efficient renewable source of energy can cut the carbon footprint of a home, according to the Eco Experts (2023), as much as 44%.
The costs for an ASHP vary depending on the dwelling’s requirements, on estimate it can cost around £10,000 but with the governments ‘Boiler Upgrade Scheme’ it subsidises the costs by £5,000 to help with changing over from traditional gas boilers to a renewable heating source.
ASHP’s operate at around 300% efficiency, so for example if it used 4,000kWh of electricity it would produce 12,000kWh of heat (which is defined by Ofgem as the average heat consumption for an average 3-bedrom home in the UK). It generally requires ASHP’s to be installed as part of a larger retrofit in order to maximise the gains as existing heating systems can be utilised, however traditional radiators require upgrading to approximately 2.5x bigger in order to be able to sufficiently heat a room at the lower running temperatures. These lower temperatures are ideal for an underfloor heating system due to the equal distribution of heat throughout a room that allows heat to radiate evenly.
Pros and Cons of Air Source Heat Pump Retrofit
Costs – For an Average 3 Bed Semi-Detached House
Air source heat pumps vary in price depending on the size of the property and the required pump to adequately service the size of the dwelling. For a 3-bedroom semi-detached property, according to the Energy Saving Trust (2023) it costs in the range of £7,000-£13,000 which on average would be £10,000. With government subsidies available to aid in the upfront costs, you could benefit from a £5,000 grant as part of the ‘Boiler Upgrade Scheme’ and also 0% VAT on purchases.
Running costs and potential savings depend upon the system the ASHP is replacing. The graph shows the different types of systems and how much savings can be made from replacing the system (based on October 2022 fuel prices). In order to maximise the slow release and lower running temperatures within existing homes, additional measures and systems are required like underfloor heating.
Further costs can be saved dependant on the temperature the end-user has the system operating at and the fabric of the building and how well the envelope of the house can retain heat.
Payback Timeframe for an Air Source Heat Pump Retrofit System
The payback timeframe of an ASHP varies, according to the annual savings graph when replacing an old oil powered boiler there are savings of around £295 annually, whereas if it is replacing an old LPG powered boiler savings can be as high as £780 annually. If we were to assume the property has an old mains gas powered boiler, with savings of £590 annually in addition to a government subsidy of around £5,000 then the payback timeframe would be around 10 years. However, according to the Eco Experts (2023) ASHP’s have a lifespan of around 20 years compared to the 10-year life span of a gas boiler, leading to further savings of roughly £4,000 by avoiding needing to replace your boiler which can be taken into consideration.
Required Space for an Air Source Heat Pump Retrofit System
Depending on the type of heat pump system you wish to utilise will change how much ‘behind the scenes’ tech is required.
An ‘air-to-air’ system utilises the external air to heat/cool rooms in winter/summer respectively and requires the standard external compressor/condenser unit along with an internal air handler to pull/push air through the dwelling. The external unit can be of varying sizes, roughly from the size of an undercounter fridge to a full height fridge/freezer depending on the requirements of your dwelling. The same can be said for the internal air handler, depending on the requirements, these vary in size. Another thing to consider for ‘air-to-air’ heat pumps is the ducting that would be required to be installed, whether that is within floor joist zones or loft spaces, it is something that needs to be considered.
An ‘air to water’ system takes the heat from outside and transfers it into a dwellings space heating or water heating. The external unit varies the same as previously mentioned, whereas the internal unit used to heat a central heating system or hot water would require a water tank, similar in size to the old school immersion heater tanks.
Conclusion
To conclude, there are two main ways in which an air source heat pump retrofit can benefit a dwelling, with the most common being air to water systems which can benefit space and water heating. They can be installed into existing heating systems however radiator upgrades are usually necessary, with the most benefits seen when in combination with underfloor heating. Available to receive up to £5,000 as part of the UK Government’s ‘Boiler upgrade scheme’ and with a longer lifespan than traditional gas boilers, they can last up to 20 years as opposed to the 10-year expected life span of a gas boiler. They are also highly efficient and safer than combustion boilers with a low carbon footprint and low maintenance requirements.
Ask us for advice
If you have a project in its infancy and want to have an informal chat regarding your options, feel free to contact us, we are always happy to provide friendly and knowledgeable advice. Get in touch on 0161 460 0382 or email the team at enquiry@pjhas.co.uk
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