What does an air-to-air heat pump do?

An air-to-air heat pump operates primarily by absorbing heat from the outside air, even when temperatures are low. This is accomplished through the refrigeration cycle, which utilizes a refrigerant that can evaporate and absorb heat at low temperatures. The heat pump extracts the thermal energy from the ambient air outside and transfers it inside to provide heating for a home or building.

This process is fundamental to the operation of heat pumps, as they can effectively heat indoor spaces by leveraging external heat sources, thereby minimizing the need for traditional heating methods. The efficiency of this system allows it to provide comfortable heating while consuming less energy compared to conventional electric resistance heating.

The other choices related to releasing heat, circulating water, and compressing refrigerant, while relevant to different aspects of HVAC systems, do not encapsulate the primary function of an air-to-air heat pump, which is centered around the absorption of heat from outside air for indoor heating purposes.