 This is possible because below ground level, the temperature is relatively constant across the seasons, and the earth can provide or absorb a large amount of heat.Ground source heat pumps work in the same way as air-source heat pumps, but exchange heat with the ground via water pumped through pipes in the ground.Ground source heat pumps are simpler and therefore more reliable than air source heat pumps (ASHP) as they do not need fan or defrosting systems and can be housed inside.