Thinking of installing a heat pump?

Here is what you need to know.

What is a heat pump?

A heat pump is a system for heating your home. It works by extracting heat from outside your house to heat the inside of your property. Here is a quick overview of how they work:

Heat energy is extracted from the air, the ground or water. Even in cold weather, there is still warmth stored in the air or ground outside your home. This heat energy is then passed over a ‘heat exchanger,’ known as an evaporator, inside the heat pump to warm up a refrigerant liquid. As it warms up, the refrigerant liquid evaporates and turns into a gas.

The refrigerant gas then moves into a compressor which increases the pressure of the gas and makes the temperature rise.

This hot refrigerant then passes over another heat exchanger, known as the condenser, and returns to a liquid. In doing so, it transfers its heat energy to warm up water used in your radiators and hot water tank.

The pressure of the refrigerant liquid then reduces, and it passes back to the evaporator to restart the process.

Of course, the above description is simplified. If you want to learn more about the mechanics, read our homeowner guide.

What types of heat pumps are out there?

There are several types of heat pump available today:

Air to water heat pumps:

These are currently the most common heat pumps in the UK. They work by extracting heat from the outside air and using it to warm up the water for your central heating radiators, underfloor heating, and hot water tank.

Air to air heat pumps:

These are like air conditioning systems operating in heating mode. They extract heat from the air outside and then transfer the energy via refrigerant pipework to heat the air inside your home using an indoor fan convector.

Ground source heat pumps:
The ground holds a lot of warmth. Ground source heat pumps extract that heat energy by using piping systems placed a few metres underground, slinkies or boreholes (going down 80-100m). The heat extracted from the ground is used to warm up the water for your central heating radiators, underfloor heating, and hot water tank.
Water source heat pumps:
Water also contains heat energy. Water source heat pumps extract heat using pipes laid under the surface of a lake or reservoir. They are not particularly common for residential applications and are mainly used for large non-domestic applications.
Hybrid heating systems:
These often combine a fossil fuel boiler with a heat pump.

Note that air to air, and air to water heat pumps are often grouped under the acronym ASHP (Air Source Heat Pump).

Can all buildings have a heat pump?

A recent UK government commissioned ‘Electrification of Heat’ research project found that all kinds of properties in the UK are suitable for heat pumps, from Victorian terraces to 1960s tower blocks and modern flats. There may be certain factors that mean a particular building cannot have a heat pump installed – such as a lack of space. But in principle, any building in any architectural style and from any era can have a heat pump.

Well insulated homes have the lowest energy costs

All heating systems work best in well-insulated homes when coupled with a suitably sized emitter system (such as radiators or underfloor heating) that provides sufficient heating power at low flow temperatures. While heat pumps can keep less well insulated homes warm too, in these cases, whichever heating appliance you choose, it would need to have a higher capacity. Less well insulated homes require more energy to maintain the desired temperature and are therefore more costly to run.
Essentially, if lots of heat is escaping through your roof, walls, and windows, then the heating system must work much harder to maintain an adequate temperature.

Some homes may need new central heating systems.

All modern heating boilers and heat pumps tend to work most efficiently with lower flow temperatures. This may mean that larger radiators (those with a larger surface area) are required in some rooms. Alternatively, if you’re undergoing major refurbishment work, underfloor heating could be considered. If you have an older central heating system, you may need to upgrade the pipework and emitters to get the full benefits of using a heat pump.

It’s worth noting that new guidance in building regulations came into effect in 2022 which means that all new heating system upgrades should run at a low flow temperature. So, even if you swap an old oil/gas boiler for a new oil/gas boiler, you may well need to upgrade your radiators and central heating system too just as you may have to when installing a heat pump.

How long will your heat pump installation take?

The short answer is that it depends.

Assuming your property is already well insulated, the radiators are suitably sized, and you are opting for an air source heat pump, the installation process can take as little as one day, although 2-5 days is more common. Ground and water source heat pumps require more time due to the necessary groundwork for the external borehole or slinky pipework.

If you are planning to upgrade your home’s insulation, you may wish to consider doing that first. Getting the insulation fitted, upgrading radiators, and then installing the heat pump could take around one to two weeks, depending on the size of the system.

What financial support is available for heat pumps?

In all UK nations, there are heat pump grants and funding available:

England & Wales

As part of the Boiler Upgrade Scheme, you can claim £7,500 towards the cost and installation of an air source heat pump and ground and water source heat pumps. As well as 0% VAT for domestic installations.

Scotland

The Home Energy Scotland Grant and Loan provides grants of between £7,500 and £9,000 (for rural homes) towards heat pumps as well as providing an interest-free loan to cover an additional £7,500.

Northern Ireland

Currently, Northern Ireland has a range of grants available. Some low-income households can apply for fully funded air source heat pumps, while people living in housing association properties can apply for grants of 50% off the price of an air source heat pump.

Find out if you need permission

In most cases, you won’t need planning permission to get a heat pump installed – they’re classed as ‘permitted developments’. There might be some situations where planning permission will be needed, such as on listed buildings. If you’re unsure, check with your local council.

How to find a heat pump installer

The short answer is that it depends.

Assuming your property is already well insulated, the radiators are suitably sized, and you are opting for an air source heat pump, the installation process can take as little as one day, although 2-5 days is more common. Ground and water source heat pumps require more time due to the necessary groundwork for the external borehole or slinky pipework.

If you are planning to upgrade your home’s insulation, you may wish to consider doing that first. Getting the insulation fitted, upgrading radiators, and then installing the heat pump could take around one to two weeks, depending on the size of the system.

Keep learning!

For many people, choosing a heat pump is a fantastic option. They are easy to use, extremely efficient, and help you reduce your carbon footprint and in some cases lower your energy bills.

Of course, it is valuable to do your research before spending time and money installing one. To learn more, read our guide to find out how this technology works. Or, read our article about what to expect from living with a heat pump.