What is a Ground Source Heat Pump?
Ground source heat pumps (GSHPs) use pipes that are buried in the garden to extract heat from the ground. This heat can then be used to heat radiators, underfloor or warm air heating systems and hot water in your home.
A ground source heat pump circulates a mixture of water and antifreeze around a loop of pipe, called a ground loop, which is buried in your garden.
Heat from the ground is absorbed into the fluid and then passes through a heat exchanger into the heat pump.
The ground stays at a fairly constant temperature under the surface, so the heat pump can be used throughout the year.
The length of the ground loop depends on the size of your home and the amount of heat you need.
Longer loops can draw more heat from the ground, but need more space to be buried in. If space is limited, a vertical borehole can be drilled instead.
Why use heat pumps?
- Heat pumps are much safer than systems that are based on combustion
- They are cheaper to run than oil and gas boilers
- The system reduces your household carbon footprint
- It has an efficient conversion rate of energy to heat
- There is minimal maintenance required.
- They have a very long lifespan of up to 50 years. As a result, they are extremely reliable and a steady source of heat
- You may be eligible for payment under the Renewable Heat Incentive (RHI) scheme
Benefits of GSHPs
Significant cost savings in heating and cooling
According to the International Ground Source Heat Pump Association (IGSHPA), GSHPs can offer between 25 and 50 percent savings on heating and cooling costs compared to conventional fossil fuel systems.
Unlike boilers or furnaces, ground source heat pumps don’t require the combustion of fossil fuels to produce heat. GSHPs do rely on electricity to run, however, and if you don’t generate your own renewable electricity, you’ll likely be running your heat pump with grid electricity, which often comes from a mix of fossil fuel and renewable sources.
Even if you run your heat pump on non-renewable electricity, the high efficiency of ground source heat pumps means that you’ll still use less fossil fuel-produced energy than with a furnace or boiler. Ground source heat pumps can be over 400 percent efficient, meaning they can convert one unit of electricity to 4 or more equivalent units of heating or cooling to your property.
GSHPs work well in almost all climates
While the efficiency of air source heat pump systems is impacted by outside temperatures (as they use the temperature of the air to collect and disperse heat), ground source heat pumps are almost completely unaffected by cold or warm climates. This is because the earth exists at an almost constant temperature underground everywhere, regardless of the air temperature above ground. Extreme climates or areas with particularly wet soils may impact the type of heat pump you’ll want to install, but in general, geothermal heat pumps work well no matter the climate thanks to the constant heat of the earth.
Is a ground source heat pump right for your home?
Is your garden suitable for a ground loop?
It doesn’t have to be particularly big, but the ground needs to be suitable for digging a trench or a borehole and accessible to digging machinery.
The ground loop can be installed in two ways, vertically or horizontally, but each will take up a certain amount of space in your garden and you’ll need to check the ground is suitable for digging.
If you want to put the pipes in vertically, you’ll need specialist machinery to drill a borehole, which will increase the cost of installation. Opting to lay the pipework horizontally is a cheaper method of installing a ground source heat pump, but you’ll need a lot more space, so it’s only suitable if you’ve got a large garden.
Is your home well insulated?
Since ground source heat pumps work best when producing heat at a lower temperature than traditional boilers, it’s essential that your home is well insulated and draught-proofed for the heating system to be effective.
If you live in England, you may be eligible for vouchers to cover up to two-thirds of the cost of installing insulation under the Green Homes Grant scheme.
What type of heating system will you use?
Ground source heat pumps can perform better with underfloor heating systems or warm air heating than with radiator-based systems because of the lower water temperatures required.
When you consider the time of year you would typically rely on your heat pump the most – when temperatures drop during the winter months – it’s easy to understand why the ground source heat pump wins in terms of efficiency. The temperature of the ground is fairly fixed at a constant 10 – 13°C all year round, so a ground source heat pump remains consistently efficient throughout the year, unaffected by seasonal changes.