A heat pump is a way of using electricity to heat your home, in an energy-efficient way. Unlike an electric panel heater, a heat pump has a compressor, which increases the amount of heat that can be generated from each unit of electricity. For a panel heater, that ratio is 1:1. For most heat pumps on the UK market today that ratio is likely to be 1:3 to 1:4, although there are many factors that can affect this.
Flow temperatures of low-temperature air source heat pumps
To achieve three or four units of heat for every unit of electricity consumed the temperature of the fluid running through a low-temperature heat pump needs to be lower than that delivered by a conventional boiler. A low-temperature heat pump runs most efficiently if it is set to run at 35°C to 45°C; in contrast a gas boiler is typically set to run between 60°C to 75°C, although the Government is currently campaigning to get all households to reduce the flow temperature on their boiler to 60°C, to save energy and reduce bills.
Compensating for lower temperatures
To compensate for lower temperatures, three things need to happen; the first of these is to improve the energy efficiency of your home, adopting a fabric-first approach, if this has not already been done. That means insulation of the floors, walls, floors, and draughtproofing. It may also mean replacing existing windows and doors.
The need for a fabric-first approach is not unique to heat pumps. With high fuel prices, reducing the amount of energy needed to keep your home warm makes sense no matter how your home is heated. Taking a fabric-first approach also means that your heating system can be sized correctly for the job it needs to do.
The second is to increase the surface area of the heat emitters. This means installing more or larger radiators and/or installing underfloor heating. The third is ensuring that you get a good handover from the installer on how to get the best from your heat pump. This means keeping the heating on for longer (as lower temperatures mean that your home heats up more slowly) and understanding that the heating system is working as it should although the radiators are no longer hot.
Advantages of high-temperature heat pumps
One of the big selling points of high temperatures air source heat pumps is that they can produce heat to the same temperature as a conventional gas boiler. This means that existing radiators can be used and there is no need for you to adjust to a new heating regime. The house heats up as quickly as it did before.
Another selling point sometimes used is that there is no need to install energy improvement measures before installing a high-temperature air source heat pump. For the reasons stated above, this is not a sustainable approach, although there maybe properties for which good levels of insulation are hard to achieve.
Disadvantages of high-temperature heat pumps
Because they heat to higher temperatures, high-temperature heat pumps use more electricity and are therefore more expensive to run than more conventional heat pumps, although cheaper than an electric panel or storage heaters. The figure of 1:2.5 units of electricity in to heat out is sometimes quoted, although (like all heat pumps) this will vary according to the season. Installing a weather compensating system is likely to improve efficiencies, by enabling the heat pump to work at its optimum operation for more of the time.
Heat temperature heat pumps are also reported to cost about 25% more to buy and install, despite it not being necessary to change radiators etc.
When is a high-temperature heat pump likely to be the best option?
A high-temperature heat pump is likely to be the best option for homes that cannot be insulated to meet current Building Regulations or better. This might be because they are Listed or in a Conservation Area or homes where the costs and risks of insulation are high – for example homes with uninsulated solid floors, in very exposed places or unusual construction.
High-temperature heat pumps may also be a good solution for tenanted properties currently heated using electric panel heaters. Installing a high-temperature heat pump will be less disruptive for the tenant and require little or no adaptation from them on how to use their new heating system.
Another reason is if you need a heat pump that can produce hot water as well as space heating and you don’t have room for a hot water cylinder – our blog ‘Can I get my hot water from an air source heat pump’ has more information on this.
Summary
If you are thinking of getting a heat pump installed, you will need to get professional advice on the system that it right for you and your home. The best place to start is to get a Whole House Retrofit Plan done for your home from a Retrofit Coordinator. If you would like help to find a Retrofit Coordinator the National Energy Foundation’s SuperHomes Team would be happy to help – you can contact them on superhomes@nef.org.uk or you could search for a Retrofit Coordinator on the TrustMark
If you’re looking for an installer you need to look for one that is certified by the Microgeneration Certification Scheme (MCS). They also have a database of installers who can install air source heat pumps part funded by the Government’s Boiler Upgrade Scheme, which until 2025 should provide £5000 toward the cost of insulation, which is well worth going for.
If the idea of enhancing your home’s energy efficiency through strategic retrofitting and delving into the realm of low-carbon alternatives intrigues you, then our SuperHomes project could be a perfect match. Our community members are at the forefront of redefining sustainable living. For further details, feel free to visit www.superhomes.org.uk
