An air-energy heat pump is a water heater that USES the energy in the air to generate heat energy. This heat is converted to indoor hot water and heating, which can provide different hot water needs for a home 24 hours a day and at the same time use the least amount of energy to meet the water needs. The air energy heat pump works according to the principle of \"reverse Carnot\". The principle of reverse Carnot cycle is that the liquid refrigerant of low temperature and high pressure is changed into the liquid refrigerant of low temperature and low pressure after being throttled by the expansion mechanism, and then enters the air switch to evaporate and absorb the heat in the air for heat exchange.