Ground Source Heat Pumps, or GSHP use a buried ground loop which transfers heat from the ground into a building to provide space heating and, in some cases, to pre-heat domestic hot water. The system does not require any external fuel and is designed to heat a whole building. Ground Source Heat Pumps are similar in concept to two common everyday items, the fridge and air conditioning unit. With a Ground Source Heat Pumps, for every unit of electricity used to pump the heat, 3-4 units of heat are produced. A GSHP uses the following components, the Ground Loop - the ground loop is lengths of pipe that are pipe buried in the ground, either in a borehole, horizontal trench or spiral horizontal. Usually this pipe is a closed circuit and is filled with a mixture of water and antifreeze, which is pumped round the pipe absorbing heat from the ground. A Heat Pump. The heat pump comprises the evaporator. This item (usually the ground loop) takes the heat from the ground with the use of refrigerants The Compressor - This item moves the refrigerant round the heat pump and compresses the gaseous refrigerant to the temperature needed for the heat distribution circuit. The Heat Exchanger - the refrigerant gives up heat to a hot water tank which feeds the distribution system. Heat distribution system - Underfloor heating, radiators or hot water storage.