Ground source heat pumps 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. Ground source heat pumps (gshp) are electrically powered systems that tap the stored energy of the greatest solar collector in existence: The earth. These systems use the earth's relatively constant temperature to provide heating, cooling, and hot water for homes and commercial buildings. As well as air source and water source heat pumps are also available.