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What is a ground source heat pump?

Joe Minihane
Written by  Joe Minihane
Kim Staples
Reviewed by  Kim Staples
Updated: 03 Nov 2023

You may have heard ground source heat pumps touted as the future of home heating. But how do they work? And is it worth getting one when your existing boiler reaches the end of its life cycle? Read on and we’ll explain everything you need to know about this eco-friendly heating system.

What is a ground source heat pump?

A ground source heat pump takes heat from the ground outside your home, via pipes in trenches or in a borehole. Using thermal transfer fluid, these pipes take this heat and pass it through a heat exchanger, which then creates hot water for radiators and water cylinders.

They are more expensive than air source heat pumps to install, but tend to offer greater efficiency and therefore more savings on energy bills. They have become a common option for larger homes looking to operate in a more environmentally friendly way and bring renewable energy into their properties.

Is it worth getting a ground source heat pump?

Getting a ground source heat pump is worth it if you want to lower the impact of your heating system on the environment. Depending on your current heating system, it may also mean lower energy bills.

The initial outlay for a ground source heat pump, however, is very expensive. You will also need to ensure you have ample outdoor space for any unground works, such as pipes and boreholes, and space inside for the heat pump unit. This will have a water cylinder for hot water and is much larger than a normal combi gas boiler.

The Energy Saving Trust says that ground source heat pumps can save as much as £560 a year compared with an old, G-rated boiler, cutting CO2 emissions by 4,500kg a year.

How do ground source heat pumps work?

Ground source heat pumps work by taking heat from the ground outside your home and using a special system to convert that heat into hot water for your heating system and taps.

On a simple level, they use pipes filled with thermal transfer fluid to take the ground-based heat and turn it into hot water by passing through a heat exchanger.

Ground source heat pumps require long trenches dug into the ground around your home, which are then filled with coiled pipes. The ground will need to be clear of any obstructions such as tree roots and easily accessible for machinery in order to dig the requisite holes.

If you do not have such space, some ground source heat pumps can be fuelled by deeper, vertical boreholes. If you have a large home, you may need multiple boreholes in order to get enough heat.

Does the government offer a grant on ground source heat pumps?

Yes, you can get a government grant for ground source heat pumps under the Boiler Upgrade Scheme. If you live in England and Wales, this grant can be up to £7,500. The UK government raised this figure in September 2023. In Scotland and Northern Ireland, you can also apply for grants and loans towards the cost of a ground source heat pump.

Before getting a grant you will need to show that your home is properly insulated. You must apply through a MCS certified contractor, who will let you know whether you have been approved and carry out the work on your behalf.

Ground source heat pumps can cost upwards of £28,000, so while a grant will help, they are still an expensive undertaking.

My boiler needs to be replaced. Should I consider upgrading?

Upgrading to a ground source heat pump is a good bet if you want to save money and slash your carbon emissions. However, the overall cost is much higher than other options – such as air source heat pumps and the most energy efficient gas boilers.

With the government extending the phasing out of gas boilers until 2035, it may be more cost effective to wait for the price of ground source heat pumps to fall. However, with climate issues becoming urgent, those who can afford to make the change may wish to consider doing so.

Will I have to upgrade in the future?

The UK government revealed in September 2023 that it was extending the planned phasing out of gas boilers from 2025 to 2035. So if you don’t want a ground source heat pump, you can get a new gas boiler for another decade at least.

The Boiler Upgrade Scheme and the fall in costs of ground source heat pumps mean that such systems should become more alluring to consumers in the future. But there is no law saying you have to do so.

Will this save me money on my bills?

If you have an old, G-rated boiler, a ground source heat pump will save you £560 per year according to the Energy Saving Trust. However, that drops to £65 compared with a new, A-rated gas boiler.

On the other hand, if you have old electric storage heaters, you could save a massive £2,200 per year.

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