Heat pumps are transforming how we heat our homes. Instead of burning fuel, they harness renewable thermal energy, cut energy costs and reduce carbon emissions.
The most common type of heat pump in the UK is the air source heat pump (ASHP). However, a ground source heat pump (GSHP) could be a better option in some circumstances, though these systems do require a fair amount of outdoor space to install.
Here we explain how much space ground source heat pumps need, plus everything else you need to know about them.
How Do Ground Source Heat Pumps Work?
Ground source heat pumps need more external space than an air source heat pump because of how they get their heat. Rather than relying on the air as a source of heat, these geothermal heat pumps extract heat from below the ground around a property.
Diluted antifreeze is pumped through a network of underground pipe loops. Because this refrigerant fluid is colder than the soil, it absorbs heat from it. The fluid is then evaporated and turned into a heated gas.
The gas then goes through a condenser. This is a high-temperature heat exchanger that transfers the heat into a water-based central heating system and the domestic hot water supply.
A ground source heat pump can also provide home cooling by reversing the heating cycle, or bypassing the refrigeration process by using cool water in the ground.
Ground Source Heat Pump Land Space Requirements
How much space a ground source heat pump needs depends on whether it’s a horizontal or vertical system.
Ground Source Heat Pump Horizontal System
Horizontal ground source heat pump systems are usually preferred because they cost less than a vertical system. However, they much bigger external space. This is because trenches have to be dug to install looped pipework at a depth of about 1.2m to 1.5m and 1m apart.
A loop of pipe can be up to 400m long, and two or more may be needed, depending on how powerful the heat pump is. A typical horizontal system requires around 700 square metres of land clear of trees and buildings. For ease of visualisation, this is slightly larger than two and a half tennis courts.
Ground Source Heat Pump Vertical System
A vertical ground source heat pump system is installed by drilling a borehole, usually 6cm to 20cm deep with a diameter of 11cm to 15cm. If more than one borehole is needed, they’re installed 5m to 6m apart.
While borehole size isn’t usually an issue, you need enough space for drilling machinery to access the site. The drilling equipment required will be about the size of a small caravan, which may be an issue in limited space areas.
Ground Source Heat Pump Indoor Unit
The ground source heat pump itself is installed indoors. A small pump may fit in a kitchen cupboard but it’s more usual to have a dedicated plant room.
A typical GSHP plant room takes up just over two square metres and houses the heat pump, hot water cylinder, pipework, and control system.
Ground Source Heat Pump Vs Air Source Heat Pump
Ground source heat pumps and air source heat pumps both generate home heating from free renewable energy in the surrounding environment.
A ground source heat pump is usually more energy efficient, so it could be a better choice particularly if you live in a colder area. Plus, ground source heat pumps have an impressive lifespan.
Efficiency
Air temperatures fluctuate more than temperatures below the ground, and an air source heat pump has to work harder as the weather gets colder. It needs to use more electricity to keep your heating at a comfortable level.
Drawing energy from under the ground is more efficient than extracting it from the air, especially in colder weather. Thermal energy in the ground remains at a more stable and generally higher temperature through the changing seasons.
This enables a ground source heat pump to average energy efficiency levels of 400% or more all year, compared with the average 300% efficiency of an air source heat pump. This greater efficiency means fewer carbon emissions and more savings on energy bills.
Lifespan
Ground source heat pumps typically last longer than an air source heat pump. When you install an air source heat pump you can expect it to last around 15 years, though with good maintenance and prompt repairs, some can last longer.
A ground source heat pump generally has a longer lifespan – around 25 years, with minimal maintenance. This is because it’s not exposed to the elements. In fact, the underground pipes can last 50 to 100 years.
How Much Does It Cost to Install a Ground Source Heat Pump?
Installing a ground source heat pump is more complex than air source heat pump installation. It therefore costs around twice as much.
The higher price is largely accounted for by the groundworks – digging trenches or drilling boreholes. Horizontal installations typically cost £16,200 to £31,000 while vertical installation can cost up to £50,000. However, grants are available that cut the cost of a ground source heat pump.
Ground Source Heat Pump Grants
Various government-backed grants are on offer towards the supply and installation cost of a ground source heat pump. Much of this funding comes from the Boiler Upgrade Scheme and the Energy Company Obligation.
Boiler Upgrade Scheme
Homeowners in England or Wales who want to install a ground source heat pump can get £7, 500 if they meet the eligibility conditions of the Boiler Upgrade Scheme (BUS). This £450 million programme is open to households who’re replacing an old inefficient heating system with a heat pump. Grants aren’t means tested so you don’t have to be receiving benefits to apply.
Energy Company Obligation
ECO4 – the fourth and final phase of the £4 billion Energy Company Obligation – covers up to 100 percent of the cost of a ground source heat pump. The scheme is open to households in England, Scotland and Wales who receive a means-tested government benefit and live in the least energy-efficient homes.
ECO4 Flex
ECO4 Flex – also called LA Flex (Local Authority Flexible Eligibility) – is an extension of the Energy Company Obligation. It provides heat pump funding to low-income households not on benefits. Local councils set their own eligibility criteria.
Why Choose a Ground Source Heat Pump?
If you have enough outdoor space such as a large garden, a ground source heat pump can provide a highly efficient, long-lasting heating system that needs little maintenance. Ground source heat pumps can produce up to five times more heat output than they use in electricity input.
This high efficiency results in significant savings on energy costs. For example, replacing an old G-rated gas boiler with a ground source heat pump can cut heating bills by around £440 year. It also reduces carbon emissions by 4,500kg a year (according to Energy Saving Trust estimated based on fuel prices as of July 2024).
Because ground source heat pumps are typically more efficient than air source heat pumps, they provide more stable, consistent heating all year round, even in colder regions. However, ground source heat pumps are considerably more expensive. That said, government grants can reduce supply and installation costs of some ground source heat pumps by a third or more. A ground source heat pump can also increase the value of your home.
Ground Source Heat Pump Advice
Home energy efficiency experts Eco Grants can help you decide whether a ground source heat pump is the right option for your property. If that’s the case, and it’s your best option, we can apply on your behalf for a heat pump grant. If you don’t qualify for funding, we can still help by finding you an impressive deal on ground source heat pump installation.