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Ground source heat pumps

Ground source heat pumps use a network of underground pipes to extract heat from the ground. This energy is then stored, ready to be used for heating your home or business. Underground heat pumps can offer a renewable alternative to standard central heating systems, helping you save money on your energy bills.

Ground source heat pumps use a network of underground pipes to extract heat from the ground. This energy is then stored, ready to be used for heating your home or business. Underground heat pumps can offer a renewable alternative to standard central heating systems, helping you save money on your energy bills.

Sofia Hutson
Energy expert
6
minute read
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Posted 16 OCTOBER 2020 Last Updated 14 MARCH 2022

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. It’s a highly efficient, low-maintenance heating system.

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 you money on your energy bills.
  • Minimal maintenance needed to keep your heating system running.
  • No storage requirements and no waiting for deliveries or running out of fuel.
  • Minimal hazards – you avoid gas emissions, risks from flammable oil or leaky gas pipes and there’s no flue to get blocked or chimney to catch fire.

Is my home suitable for a ground source heating system?

Your home could be more suitable for a ground source heating system if it’s:

New - ground source heating systems work best with newer, well-insulated homes. This is because heat pumps are more efficient when they don’t have to raise the temperature of the heat they extract by too much. A draughty old property will need more heat to keep it at a comfortable temperature than a double-glazed, well-insulated modern home. 

It can also be cheaper to install a ground source heat pump in a new build than have one retrofitted to an old property. Putting underfloor heating in from the start, for example, is easier.

Off the gas grid - ground source heat can be a sensible choice for homes where other options such as gas aren’t available.

Has a large garden - 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. If you don’t have the garden space available, you might instead want to consider an air source heat pump

But having an old home doesn’t mean you should rule out ground source heating. Instead, at the time of installing a system, you should also improve the insulation in your property - for example by installing loft and cavity wall insulation. 

And for some people, the ecological benefits are all important. You’ll want to weigh up the pros and cons, including the costs.

How much space does a ground source system need? 

You’ll need around 2.5 to 3 times the floor area of your home to install the ground loop in your garden as a rule of thumb. But again, this will depend on how much heat needs to be produced and how well your home is insulated.

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.

Data from IMS Heat Pumps 

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. 

You’ll also need space for a plant room inside your home for the heat pump itself. 

Domestic ground source heat pumps are typically allowed as permitted developments. But the rules can be complex, so you should check with your local authority to see if you need planning permission to go ahead – especially if yours is a listed property.

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. 

Ground source heat pumps should be considered a long-term investment. But once the system is up and running, it 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. However, the costs of installation may mean that it takes some time for payback on your original outlay.

Frequently asked questions

Are grants still available to help pay for the installation of heat pumps?

A couple of the schemes put in place to help the UK achieve its green goals have now closed. 

The Domestic Renewable Heat Incentive (RHI) scheme offers quarterly payments to people who produce energy using eligible sources. However, that scheme closed to new applicants from 31 March 2022, although it will continue to pay out for people already in the scheme. 

The Green Homes Grant, which the government set up to fund energy efficiency upgrades in domestic homes with grants of £5,000-£10,000, has also closed. 

The remaining option you may be able to use is the Green Deal scheme. It’s open to any household with an electricity meter (including prepayment meters) in England, Scotland or Wales - but not Northern Ireland. Your Green Deal assessor would need to recommend a ground source heat pump as a suitable improvement for you to be able to get a grant through the scheme. See more about the Green Deal on GOV.UK.

If you live in Scotland, you may be eligible for a Home Energy Loan to help you pay for the installation of a ground source heating system. There’s a maximum loan of £10,000 available and you may be able to claim cashback for certain energy efficiency measures and renewable heating systems – including ground source heating. 

If you live in Wales, you might be eligible for free home energy efficiency improvements if you receive means tested benefits or someone in your home has a chronic health condition. See more about who is eligible on the Nest website

If you live in Northern Ireland you can find out about grants on the nidirect website.

What’s the difference between running gas central heating and ground source heating?

Heat pumps are at their most efficient running for longer at lower temperatures. So instead of having your gas heating on for half an hour before you get up, you may need it on for longer in the morning.

Likewise, you might find that during the evening you’re better off with your heating running for longer at a lower temperature. Your installer should be able to advise you on getting the best out of your system.

How can I find a good ground source system installer?

You need to make sure your system is designed and installed by qualified experts. Ideally, you should get independent expert advice from an MCS-certified installer about whether a heat pump is the right technology for you and your home.

MCS certifies low-carbon products and installations used to produce electricity and heat from renewable sources. Installers it certifies have to follow a consumer code, which gives you an added level of protection.

How noisy are ground source systems?

Ground source heat pumps are generally quieter than a gas boiler. They’re also quieter than air source heat pumps.

How long do ground source heat pumps last?

With annual servicing, the heat pump itself should last around 20-25 years – compared with gas boilers, which last around 10-12 years. The ground loop kits (which are used to collect the heat energy) can last for 70-100 years.

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