Heat pumps using a certain amount of effort to allow for movement of the coolant, the amount of energy deposited at the hot side is greater than that which is deposited on the cold side. Common heat pumps, operate by exploiting the physical properties of a liquid evaporation and condensation, known as the coolant. The cycle diagram of a heat pump vapor compression refrigeration, consists of: 1) Condenser. 2) Expansion Valve. 3) Evaporator. 4) Compressor. 

The low pressure liquid refrigerant exits the expansion device and into another heat exchanger which is called evaporator, where the liquid absorbs heat and boil. The refrigerant then returns to the compressor and the cycle repeats. In this system, it is essential that the coolant reaches sufficiently hot when it is compressed, and the second law of thermodynamics prevents heat flow from a cold liquid to a heat sink. In practice, this means the refrigerant must reach a temperature higher than the ambient around the heat exchanger high temperature. 

A home water heating system operates using a circulation pump to move hot water from a boiler through a series of metal pipes. Heat is given off as the water flows through the piping and back into the boiler. The heat generated by the hot water in the pipes can warm a room in a house. A circulating water pump is turned on and off to move hot water through the pipes, and maintain a set temperature in the room. Water cooling systems operate very similarly but use cold water for cooling.

Gravity furnaces are heating equipment that employ the use of gravity to conduct warm air to various parts of the structure. At one time, this type of furnace was a common means of providing heat in homes and apartment buildings. While this type of furnace has been replaced in many case by devices such as the heat pump, there are still many homes that continue to make use of a gravity furnace.

The function of a gravity furnace is relatively simple. Typically, the furnace proper is usually housed in the basement area of the home or building. Different types of heating fuels may be used, such as electricity, coal, oil or gas. When active, the furnace distributes the produced heat into the upper levels of the dwelling by the means of ductwork that is ran throughout the walls and floors of the building. Vents that are strategically attached to the ductwork allow the hot air to escape into the rooms of the home. This design is sometimes referred to as an octopus furnace.

Baseboard heaters generally do use separate thermostats, however, making them an excellent choice for spaces that are used and heated only infrequently. They also require a great deal of wall space and can make finding space for shelves or furniture somewhat difficult.

The piping connects to a boiler, which circulates water or a special heat-producing fluid through the supply end of the pipes. Cooled fluid returns to the boiler, through the other end pipe, for recirculation when the thermostat calls for heat. This system can operate on a variety of fuel sources, including electricity, oil, propane and natural gas. Hydronic floor heating offers efficiency and distributes heat more evenly than the more common forced-air heating system.

Geothermal alternate heating systems rely on the natural ground temperature of the Earth. The temperature not far below the surface typically stays at a consistent 55° to 60° Fahrenheit (12.8° to 15.6° Celsius). A heat pump installed in the building has the capacity to both heat and cool the structure. The unit circulates warm water through pipes installed underground.

 

The outside coils of air source heat pumps are installed on an outside wall or concrete pad in a location where the unit has plenty of room for air movement. If the air source heat pump is installed in an area where the outside coils will be heated by the sun, it can further improve the unit's efficiency.