An air source heat pump system consists of a compressor and two coils made of copper or aluminum tubing; one coil is located indoors and the other one is located outdoors. In the winter, liquid refrigerant in the outdoor coil converts into a gas after absorbing heat from the air. In the indoor coil, heat is released from the gas refrigerant as it condenses back into liquid.
How does cold air provide heat?
Hot and cold are relative terms. All outside air down to absolute zero (-460°F) contains some heat. An air-source heat pump extracts some of this heat and moves it indoors to provide space heating.
In the summer, an air source heat simply works in reverse to provide highly efficient cooling. It takes heat from the warm indoor air and moves it outside.
Split-ductless air source heat pumps—also called mini splits—don't require ductwork, making them perfect for additions or homes without ducts. Ductless systems include an outdoor unit and one to four indoor air handlers. Tubing that circulates refrigerant connects the indoor and outdoor units. The indoor air handlers are typically mounted on a wall or ceiling and are controlled remotely.
Air source heat pump efficiency
Air source heat pump heating efficiency is measured by heating seasonal performance factor—the total heating output of the unit during the heating season divided by the electricity consumed. The higher the HSPF, the more efficient the unit. ENERGY STAR®-qualified heat pumps must have a minimum HSPF of 8.5.
Cooling efficiency for air source heat pumps is indicated by seasonal energy efficiency ratio (SEER)—the total amount of heat removed from the home during the cooling season divided by the energy used. Once again, a higher SEER is better. ENERGY STAR units must be rated at 15 SEER or higher.
Air source heat pumps can reduce your energy use for heating by 50% compared to conventional technologies, such as furnaces and electric resistance heating. High-efficiency heat pumps also dehumidify better than standard central air conditioning systems, resulting in improved comfort and lower energy usage in the summer.
Traditionally, air source heat pumps worked best in moderate climates with mild winters. However, advances in technology now make them a good option for colder climates. The Northeast Energy Efficiency Partnership (NEEP) developed a Cold Climate Air Source Heat Pump (ccASHP) Specification and Product List that includes the heating capacity and efficiency down to 5°F. Ask your contractor to check it out and help you decide if a Cold Climate Air Source Heat Pump is right for you.
If your heating or cooling system is older or you are considering an addition, an air source heat pump is a good choice for cost-effective year-round comfort.