As more and more people look for sustainable ways to run their homes, technologies like ground source heat pumps are growing in popularity. But what is it and can you install it in your home?

What are they?

The pumps take energy from the ground and pump it up to your home via pipes installed below the surface, where thermal energy is consistent.

The pumps circulate water and antifreeze around the pipe, which absorbs heat and passes it through a heat exchanger into the heat pump. The longer the pipe the more heat you’ll get. As the temperature this far down is fairly constant, it means the pumps aren’t reliant on the variable British weather and can be used all year round.

While they’re fairly adaptable, there is one big thing you need – ground. This means they’re not suitable for individual flats, though some new developments are installing them via boreholes on the pile foundations.

You’ll also need to find out if your garden could be dug down far enough to install the system – typically only around 1m, but some properties have water tables that are higher than this.

Will they save me money?

Ground source heat pumps are expensive to install and maintain. But the idea isn’t just about saving money, but about being more efficient and sustainable. Though over time, as the heat you’re getting is essentially produced for much less, you can save money.

The Energy Saving Trust (EST) says it costs between £13,000 and £20,000 to install the system. Over time, the money saved can start to pay this back but it depends on a variety of factors from how efficient the system is to what sort of system you are replacing.

If you’re getting rid of a dated boiler then you’ll make your money back faster. But if you’re replacing a fairly new combi boiler, the savings will be much less. The EST says an average ground source heat pump can save you up to £1,500 a year if you’re replacing an old LPG-fired heating (non-condensing) system. But this could drop to £150 if replacing a more modern gas boiler.

Additionally, you could actually have the system paid for through the Government’s Renewable Heat Incentive (RHI). This scheme aims to encourage the uptake of renewable heat technologies and pays a subsidy over 7 years that is roughly the cost of the installation.

Are they popular?

At the moment in the UK, the answer is no. They currently make up less than 1% of all heating appliance sales in both domestic and commercial buildings, compared to places like Sweden and Switzerland where the figure is closer to 20%.

But the government is looking in to ways to increase usage as they feel a mass market for ground source heat pumps would decrease the costs associated with them and make them a more appealing option.

In the past decade, the market for heat pumps in the UK has grown and matured, partly due to the RHI subsidies. This has led to more pumps becoming available and a better understanding of not just what they can do, but how to get the best from them.

This has been especially important among installers, as while there are a number of models available, a lot comes down to how well they are installed and maintained.

And it’s not just ground source heat pumps that are available. Air source heat pumps are cheaper, but can perform poorly in cold temperatures. Water source pumps can use nearby rivers or lakes for their heat and are similar in performance to ground source.

For new properties

The Government is pushing to make heat pumps the first option for heating systems when it comes to new builds, ahead of boilers.

As new homes are being built to higher insulating standards than ever before, heating costs have been reduced and the need for boilers reduced. Pumps work best with features like under-floor heating, which many new homes are installed with. Heat pumps can be matched to new buildings so they are the right size to provide low levels of heat that help maintain comfortable homes.

Essentially, they can provide a constant low level heat that removes the need for boilers going on and off. This has the effect of heating the whole home, including the structure and walls. These structures retain the heat and release it when the home starts to cool, helping to maintain a steady temperature.

If installed correctly, they can also be used to generate hot water and run radiators. Though the radiators need to be larger to increase their surface area and offset the lower temperatures generated by the pumps.

For existing homes

While they can be used to replace existing heating systems, a number of changes need to be made to the property. This often includes adding insulation, replacing single-glazed windows and improving draft proofing.

These measures will reduce the heat demand of the home, allowing heat pumps to be installed. Again, if you’re using it with radiators, you may need to replace these with larger ones to increase the total surface area.

No matter which system you go with, you need to find an installer with pedigree. The installer should go through a number of factors with you before and after installation. These include how the system will integrate with your home, how to control it depending on the thermal properties of your home, how often it needs to be maintained, and the cost of maintenance.

Maintenance costs can be more than standard boiler, but a lack of maintenance can lead to costly breakdowns. The engine in a heat pump is a compressor. If it fails, the only option is to replace it, which can cost £1,500 and up. This means annual maintenance is key.