Air, as the low-temperature heat source for heat pumps, is inexhaustible. The research, production, and application of air-source heat pumps (also known as air-cooled heat pumps) in China experienced rapid development in the late 1980s. Current products include residential heat pump air conditioners, commercial unitary heat pump air conditioning systems, and heat pump hot and cold water systems. The installation and operation of air-source heat pumps are both convenient, with reliable systems and no environmental pollution. The air-source heat pump hot and cold water systems are modularly designed, eliminating the need for standby units. They operate with automatic computer control during operation, adjusting the unit's operating status to match the output power with the working environment.