Ground Source Heat Pumps

South Thames Gas is an EarthEnergy™ approved installer of ground source heat systems.

This system utilises the energy in the ground to provide all the heating and hot water your home requires. The principle is simple, and the result is low-cost comfortable heating that uses sustainable energy and causes no direct emissions or other damage to the environment.

For every single kilowatt of electricity used to power the heat pumps, this system could generate four kilowatts or more in heat for your home. This technology is reliable, sustainable and can reduce heating energy consumption by up to 75%. And it gets even better – most electricity suppliers are now offering ‘clean green’ electricity from a renewable energy source, and if you use this to power your heat pump, your property will be totally heated from renewable energy with zero CO2 emissions! You can also apply for a government grant towards the cost off installation under its Low Carbon Building Programme.

A heat pump can take low temperature heat and upgrade it to a higher, more useful temperature. If this heat comes from an ambient source, for example outside air or the ground, the use of a heat pump can result in savings in fossil fuel consumption and thus a reduction in the emission of greenhouse gases and other pollutants. Ground Source Heat Pumps (GSHPs) in particular are receiving increasing interest in North America and Europe and the technology is now well established with over 550,000 units (80% of which are domestic) installed worldwide and over 66,000 installed annually.Despite increasing use elsewhere, GSHPs are a relatively unfamiliar technology in the UK although the performance of systems is now such that, properly designed and installed, they represent a very carbon-efficient form of space heating.


A GSHP system consists of a ground heat exchanger, a water-to-water or water-to-air heat pump, and a heat distribution system.

Until recently open-loop GSHP systems using groundwater were the most widely used type. Where a suitable source of groundwater is available this can be very cost effective because water can be delivered and returned using relatively inexpensive wells that require little ground area. However, the disadvantages are that water availability is limited, fouling and corrosion may be a problem depending on water quality and most importantly environmental regulations covering the use of groundwater are becoming increasingly restrictive.

These limitations mean that interest is now focused on closed-loop or ground coupled systems, where the ground heat exchanger consists of a sealed loop of pipe buried either horizontally or vertically in the ground. The refrigerant can be circulated directly through the ground heat exchanger in a direct expansion (DX) system but most commonly GSHPs are indirect systems, where a water/antifreeze solution circulates through the ground loop and energy is transferred to or from the heat pump refrigerant circuit via a heat exchanger. Although more expensive than open-loop systems, closed-loop systems are more widely applicable. This guide will only consider closed-loop systems.


GSHPs can be used to provide space and domestic water heating and, if required, space cooling to a wide range of building types and sizes. The provision of cooling, however, will result in increased energy consumption however efficiently it is supplied. GSHPs are particularly suitable for new build as the technology is most efficient when used to supply low temperature distribution systems such as under floor heating. They can also be used for retrofit especially in conjunction with measures to reduce heat demand. They can be particularly cost effective in areas where mains gas is not available or for developments where there is an advantage in simplifying the infrastructure provided.

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South Thames Gas
62 Railton Road
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