Ground Source Heat Pumps

Ground source heat pumps draw heat from the ground via a network of water pipes buried underground (rather than the ambient air via an air source heat pump)

A mixture of water and anti-freeze (known as a thermal transfer fluid) is pumped around the ground loop and absorbs naturally occurring heat from the ground. The thermal transfer fluid is compressed and goes through a heat exchanger, which extracts the heat and transfers it to the heat pump. The heat is then transferred to the heating system to provide usable heat.

A ground source heat pump can typically increase the thermal transfer fluid temperature from the ground to around 50°C. Whilst it is possible to heat to higher temperatures, it will reduce system efficiency and require the consumption of more electrical energy.

How Ground Source Heat Pumps Work

Our diagram below showcases how this works:

Ground Source Heat Pump Facts

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Average cost is between £14-19k/€16-22k1

Properly Installed ASHP will return 4kWh of heat for every 1kWh of electricity

Typically saving around £870-£960/€1k per year compared to electric heating1

With regular maintenance, indoor components should last 20 years and ground loops last 50 years or more

To work provide the best operational savings a well-insulated building is essential.

GSHP’s are often be best suited to new-build properties where the central heating system can be optimised for use with the lower temperature thermal source than compared to conventional boilers. Whilst GSHP’s generate less CO2 than conventional heating systems they still need to use electricity to drive the pump. Therefore, they cannot be considered completely zero-carbon unless the electricity is provided by a renewable source.

The cost of installing a GSHP is significantly more expensive than an ASHP. The Energy Saving Trust (EST) estimate that the cost of installing a typical GSHP system ranges between £14,000 to £19,000, depending on the size of the system and excludes the cost of fitting underfloor heating and/or radiators. However, they usually require less electrical energy to recover an equivalent amount of thermal energy than that of an ASHP

GSHP’s usually require little maintenance and can provide heating and hot water, however need enough space outside the property for the external horizontal ground loops or vertical boreholes. Whilst they are more complex to install than air source heat pumps, they avoid the external noise issues associated with ASHP’s. GSHP’s also typically require planning permission due to the requirement to bury a significant area of ground loops.

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1 Energy Saving Trust April 2020 figures