Glossary · Heat pumps, grants and regulations
What is a ground source heat pump?
A ground source heat pump heats your home and hot water using the steady low-level heat in the ground. A loop of buried pipe carries a water and antifreeze mix that absorbs the heat. The heat pump then raises its temperature for radiators or underfloor heating. It needs outdoor space and runs on electricity.
Key points
- A ground source heat pump circulates water and antifreeze through buried pipes, then raises the temperature of the heat it collects to warm your home and water.
- It needs a lot of outdoor space for horizontal pipes in trenches 1 to 2 metres deep. Vertical pipes need specialist machinery and cost more.
- MCS gives an average installation cost close to £25,000, compared with around £13,300 for an air source heat pump in 2025.
- The Boiler Upgrade Scheme currently gives £7,500 towards a ground source heat pump, including water source heat pumps and shared ground loops.
- MCS says ground source heat pumps have the lowest carbon output of any heat pump type.
How a ground source heat pump works
A ground source heat pump circulates a mix of water and antifreeze around a loop of pipe buried in your garden. The constant low-level heat in the ground warms the fluid in the pipes. The heat pump then condenses that heat to raise its temperature, and transfers it into your home to provide heating and hot water.[1]MCS, Ground/water source heat pumps Once the heat has been taken, the fluid returns to the underground pipework to absorb more heat.[1]MCS, Ground/water source heat pumps
A ground source heat pump is a type of heat pump, a device that moves heat from outside into your home using electricity rather than generating the heat itself.[1]MCS, Ground/water source heat pumps It can be linked to smart heating controls. MCS says ground source heat pumps have the lowest carbon output of any kind of heat pump.[1]MCS, Ground/water source heat pumps
Types, space and cost
MCS describes ground and water source heat pumps together.[1]MCS, Ground/water source heat pumps
| Type | How it collects heat | Notes |
|---|---|---|
| Horizontal ground loop | Pipes in trenches, usually 1 to 2 metres deep | Cheaper and chosen by most people. Needs a large garden |
| Vertical ground loop | Pipes put down vertically | Useful when space is tight. Needs specialist machinery, so costs more |
| Closed-loop water source | A submerged pipe network in a river, lake or canal | Needs a nearby water source |
| Open-loop water source | Uses water directly from the source | Needs a nearby water source |
Some installers work out the space needed as 50 to 80 metres of pipe per kilowatt. Some suppliers quote an overall area of 700 square metres. Your garden also needs to be suitable for trenches to be dug, with easy access for digging machinery.[1]MCS, Ground/water source heat pumps
The average installation cost is close to £25,000, varying with the size and age of the property.[1]MCS, Ground/water source heat pumps MCS puts the average cost of an air source heat pump at around £13,300 in 2025.[2]MCS, Air Source Heat Pump For comparison with air source, see our air to water heat pump page.
The Boiler Upgrade Scheme currently gives £7,500 towards a ground source heat pump, including water source heat pumps and those on shared ground loops. Until March 2027 there is an extra £1,500 if the property is heated by oil or LPG and has no mains gas connection. The maximum capacity is 45kWth for individual systems and 300kWth for shared ground loops.[3]GOV.UK, Apply for the Boiler Upgrade Scheme: What you can get The installer applies for the grant on your behalf and the value is taken off the amount you pay.[5]GOV.UK, Apply for the Boiler Upgrade Scheme: How to apply
What happens at commissioning
Approved Document L says heat pumps should be commissioned in accordance with the manufacturer’s instructions and the system design parameters. For a ground source heat pump, the ground array including header pipes and manifolds should be flushed as one system to remove debris and purged to remove air.[4]Ministry of Housing, Communities and Local Government, Approved Document L, Conservation of fuel and power, Volume 1: Dwellings, 2021 edition incorporating 2023 amendments The guidance also says a wet heating system that is newly installed or fully replaced should be sized to work at a maximum flow temperature of 55°C or lower where feasible.[4]Ministry of Housing, Communities and Local Government, Approved Document L, Conservation of fuel and power, Volume 1: Dwellings, 2021 edition incorporating 2023 amendments That is work for your installer, and part of why an MCS certified installer is the right choice.
Example
Neil lives in a detached house with a large garden near Otley. He has an oil boiler and wants to move away from it. His MCS certified installer surveys the garden and finds room for a horizontal ground loop. The installer quotes a cost, applies for the Boiler Upgrade Scheme on his behalf and shows the £7,500 grant, plus the extra £1,500 for oil heating, taken off the invoice. Neil compares this with an air source heat pump quote, which MCS says costs less on average.
What people get wrong
People often assume that a ground source heat pump digs deep into the ground. Most take heat from pipes laid in trenches 1 to 2 metres deep. Deep vertical pipes are an option when space is tight, but they need specialist machinery and add to the cost.
The second mistake is to underestimate the space. Horizontal loops need a large garden and access for diggers. Ask your installer to survey the site before you decide, and ask about the coefficient of performance and seasonal figures the manufacturer quotes.
The bottom line
A ground source heat pump collects low-level heat from the ground using buried pipes and raises its temperature to heat your home and water. MCS gives an average installation cost close to £25,000, and the Boiler Upgrade Scheme currently gives £7,500 towards it. It needs outdoor space and a survey first. MCS says most properties have enough space for an air source heat pump, so that is the usual comparison.[2]MCS, Air Source Heat Pump See our heat pump page.
Common questions
How much space does a ground source heat pump need?
MCS says some installers work on 50 to 80 metres of pipe per kilowatt, and some suppliers quote an overall area of 700 square metres. Horizontal pipes are laid in trenches 1 to 2 metres deep. If space is tight, vertical pipes can be used but need specialist machinery.
How much does a ground source heat pump cost?
MCS gives an average installation cost close to £25,000, varying with the size and age of the property. The Boiler Upgrade Scheme can take £7,500 off if you are replacing a fossil fuel heating system.
Is a ground source heat pump better than an air source one?
MCS says ground source heat pumps have the lowest carbon output of any kind of heat pump, but they cost more to install and need much more outdoor space. Which suits a home depends on its size, garden and heating system.
Do ground source heat pumps need MCS certification?
To claim the Boiler Upgrade Scheme grant the installer must be MCS certified. MCS certified installers use MCS certified ground and water source heat pumps, which have been tested for quality, reliability and performance.
Sources
We cite the original source for every figure: government, regulators, standards bodies and manufacturers' own documents. Each one shows the date we last checked it.
- MCS. Ground/water source heat pumps. Checked 11 November 2026. ↩
- MCS. Air Source Heat Pump. Checked 11 November 2026. ↩
- GOV.UK. Apply for the Boiler Upgrade Scheme: What you can get. Checked 11 November 2026. ↩
- Ministry of Housing, Communities and Local Government. Approved Document L, Conservation of fuel and power, Volume 1: Dwellings, 2021 edition incorporating 2023 amendments. Checked 11 November 2026. ↩
- GOV.UK. Apply for the Boiler Upgrade Scheme: How to apply. Checked 11 November 2026. ↩