One of the most efficient and least environmentally-damaging homes heating option is a heat pump. These come in two varieties: air-source and ground-source.
Air-source heat pumps draw heat out of the atmosphere (even on cold days), concentrate the heat using refrigeration technology, and then distribute the heat through the house, usually through a duct system or through pipes.
Ground-source heat pumps, also known as geothermal systems, concentrate heat from the earth via pipes buried roughly one to two metres beneath the surface, or in vertically drilled bore holes that typically run a couple of hundred feet deep.
Heat pumps are powered by electricity, but because they extract free heat directly from the air or ground, they are extremely efficient. As a general rule, for every kW of electrical energy consumed by an air-source heat pump, you’ll get about three kW of heat. For ground-source systems, the ratio is about one to four. In addition, some heat pumps can be run in reverse to cool a building during summer periods, by extracting heat and transferring it to the ground thus helping to recharge the ground loops ready for winter. Systems can also be connected to domestic water heating systems to provide a large portion of domestic hot water.