Ground source heat pumps harness the free and renewable energy sources in the ground to help  heat your home and supply hot water at a very low cost. 

Geothermal Heat Pumps, also known as Ground Source Heat Pumps (GSHP) 'pump up' heat from a low temperature source (e.g. the ground or the air) and release it at a higher temperature into your central heating system. The easiest way to explain how it all works is with these three diagrams.