Ground source heat pumps

Under-ground temperatures, where pipes are laid, are generally higher than air temperatures during the winter months. This means there is useful energy available, all year round, which can be extracted by ground source - and indeed ground source - heat pumps. You can measure this in operation anytime, by opening your refridgerator or freezer and comparing the temperatures of the icebox and the 'element' at the rear.

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 the garden. When the liquid travels around the loop it absorbs heat from the ground - used to heat radiators, underfloor heating systems and even hot water.

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.

Normally the loop is laid flat, or coiled in trenches about two metres deep, but if there is not enough space in your garden you can install a vertical loop to a depth of up to 100 metres.

The efficiency of a ground source heat pump is measured by a coefficient of performance (CoP) - the amount of heat it produces compared to the amount of electricity needed to run it. A typical CoP for a ground source heat pump is around 3.2 without any reductions for the type of distribution system.

The benefits of ground source heat pumps

• Reduce your CO2 emissions: on average a ground source heat pump could save around 540kg of carbon dioxide every year when replacing an oil boiler.

• Eliminate your fuel bills: ground source heat pumps run on electricity, so there's no need to pay for gas, oil or solid fuels to heat your home.

• Cut down on wasted electricity: heating your home with a ground source heat pump is much more efficient than using electric radiators