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Peter Earl
From the Energy team
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Posted 19 OCTOBER 2020

How do ground source heat pumps work?

During the day, the ground absorbs heat from the sun’s rays. Ground source heat pumps extract this heat energy, using a series of underground pipes filled with a mixture of water and anti-freeze, storing it much like a fridge working in reverse.

The water mixture is then put through a compressor to enhance the heat, before it goes through a heat exchanger. It can then be used to heat homes. Ground source heat pumps are also sometimes known as geothermal pumps.

Energy produced by ground source heat pumps can be used for hot water, but it’s most effective in underfloor heating systems. Typically, they deliver heat at a lower temperature but over a longer period, which in a well-insulated home will keep you cosy.

Are ground source heat pumps a renewable energy source?

Yes. Ground source heat pumps use heat from the sun to produce thermal energy that we can use in our homes.

The pumps do need some power to run. However, they can generate up to four times as much energy as they use depending on the temperature, making ground source heat a sustainable source of thermal energy.

The benefits of ground source heat pumps

Ground source heat pumps could offer a reliable, greener way of heating your home compared to a standard boiler system.

Here are some advantages of installing a ground source heat pump:

  • More environmentally friendly because it produces lower carbon emissions than both oil and gas heating.
  • Save money on your energy bills.
  • Earn money back on your energy through the Government’s Domestic Renewable Heat Incentive (RHI), making money from the excess energy you produce.
  • Minimal maintenance needed to keep your heating system running.

Is my home suitable for a ground source heating system?

A ground source heat pump takes up a fair amount of underground space. This means your garden has to be a considerable size and easily accessible to have the equipment installed.

A typical heat pump system will need a two-metre-deep trench. At this depth the temperature tends to remain constant all year. The length you’ll need depends on several factors, including:

  • Type of soil
  • The size of your heat pump
  • Whether pipes will be straight or coiled. Coiled pipes may require wider trenches which can add to the installation costs, but can reduce the length of the trench required.

As a guide, a 10kW Vaillant FlexoTherm ground source system would need at least 700 square metres of land space to lay down three 200-metre long loops**.

If you have a smaller garden but really want to install this kind of system, you could consider a vertical ground source heat pump using boreholes. These systems tend to be more costly to install, as special machinery will be needed, and the installation might not be possible in tight urban spaces.

Domestic ground source heat pumps are typically allowed as permitted developments. However, you might need to seek planning permission if you want to have one installed, especially if yours is a listed property. Before you have a system installed, consult with your local council. And remember, you’ll also need space for a plant room.

It can be cheaper to install a ground source heat pump in a new build, than have one retrofitted to an old property. A report by the Department for Energy and Climate change estimated it could be 10% cheaper. But for some people, the ecological benefits are all important. You’ll want to weigh up the pros and cons, including the costs.

How much does a ground source heat pump cost?

The initial costs of installing a ground source heat pump can be daunting – expect to pay at least £10,000-£20,000. But it could be as high as £35,000 depending on the size of your home, your needs and the groundworks required.

Getting the pipes underground is typically the most expensive part of the project.

The boiler can cost around £7,000 to £11,000, with typically a minimum of an 8kW boiler for a three-bedroom home. The rest of the cost is made up by the groundworks and the plant room.

Ground source heat pumps should be considered a long-term investment. However, once the system is up and running, ground heat source pumps should be very low maintenance.

Can ground source heat save you money on your energy bills?

Ground source heating is far more efficient than a standard boiler system, so it can be a great way of saving money on your energy bills.

There is also the potential to make money from the renewable energy you produce. The Government’s RHI scheme offers quarterly payments for people who produce energy using eligible energy sources. People who run ground source heat pumps could receive payments for seven years for the amount of renewable heat they produce.

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**Data from IMS Heat Pumps

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