The vast majority of home heating systems burn fuel in a furnace to heat air or water that acts as the transfer agent to spread the heat from the furnace throughout the house. Most systems burn natural gas, propane, fuel oil, coal or wood to heat the home. But there are two major alternatives to combustion-based home heating systems: solar heat and electric heat pumps.
Solar heating systems use the sun's thermal energy to provide space heating and hot water for homes. The two types of solar systems are active and passive. Active systems use a solar collector to collect the sun's energy and a pump or blower to move water or air between the collector and the living spaces. Passive systems rely on the home's design and structure to collect solar heat and rely on super insulation to retain the heat. Heated air or water moves through the house by natural convection. The advantage is that the heat you collect is free. The drawbacks are high initial cost and the fact that the sun doesn't shine all the time, so a backup heating system may be needed.
Air-Source Heat Pump
A heat pump is an electrically-powered device for moving heat into or out of a room. The most common type of heat pump is the air-source heat pump. This device uses an electric compressor to transfer heat from the outside air into your house. In summer, the action can be reversed to transfer heat from inside your home to the outside. This type is fairly efficient, cutting heating costs by about 30 per cent. Air source units' efficiency drops off sharply as the outside air gets colder, making them practical only in climates with moderate heating and cooling needs.
Geothermal Heat Pump
Ground-source (geothermal) heat pumps draw heat from the ground and use it to heat the home. The system uses a loop in the ground filled with an antifreeze solution and an electric pump that circulates the fluid through the loop, much like a refrigerator in reverse. The system absorbs heat from the ground and transfers that heat to the building via a heat exchanger. They can be reversed to cool the building. These systems are extremely efficient and can cut heating costs up to 70 per cent. The drawbacks are very high initial installation cost and the need for a very large lot. Their performance declines in cold climates, but not as much as with an air-source heat pump..