The average ground temperature just below the surface, in the UK is between 8ºC and 13ºC, this temperature remains constant throughout the year. EarthEnergy™ systems circulate water through pipes buried either horizontally or vertically in the ground. The water in the pipes is lower than the surrounding ground and so it warms up slightly. This low grade heat is transferred to a heat pump, where it is used to heat up a refrigerant. By compressing this 'warmed' refrigerant further heat is generated and this means that water output from the heat pump is typically 45ºC - 50ºC for space heating and up to 55ºC for domestic hot water