A heat pump is an integrated cooling and heating system. The system cools your house during the hot season by extracting heat indoors and dumping the heat outside. During the cold season, the same system warms the house by extracting air from outside the house and bringing it indoors. Below are some of the various types of heat pumps available today.
Air-Sourced Central Heat Pump
This type of heat pump operates like a central AC. The heat pump comes with a condenser outside the house, an evaporator inside the house, and a duct system to circulate the air. During the hot season, the heat pump operates just like any other AC by extracting heat from the air inside the house and dumping the heat to the outside air.
During the cold season, the functions of the evaporator and condenser are reversed. The heat pump then extracts heat from the air outside the house (there is always some heat in the air unless it's absolutely cold) and brings it inside. The air-sourced heat pump reduces when it gets terribly cold, at which point you may need a furnace or another heating system.
Ground-Sourced Heat Pump
A ground-sourced heat pump is also referred to as a geothermal heat pump. A ground-sourced heat pump works more or less the same as an air-sourced heat pump. The main difference is that it is the ground, rather than the air, that is used for heat exchange.
The substitution of ground/earth for air is a crucial one. The earth does not lose heat as easily as the air, and ground temperatures tend to be steady throughout the year. In fact, the ground is warmer than the air during the winter and colder than the air during the summer. This makes it easy for a geothermal heat pump to extract heat outside the house and bring it indoors during the winter season, and extract heat inside the house and dump it into the ground during the summer. These heat pumps operate in much colder climates than the air-sourced heat pumps are able to do.
Ductless split heat pumps are comparable to ductless air conditioners. A ductless split heat pump, as the name suggests, does not rely on ductwork. Instead, the system has an indoor unit that comprises the evaporator coil and a fan; the fan circulates the required air (hot or cold) in the room. You will need a unit (containing an evaporator and a fan) in each room you want to heat or cool. Again, the operations of the indoor and outdoor units are reversed when the season changes.
For more information, contact a residential HVAC contractor in your area.