At present, solar water heaters are popular in the domestic hot water market with their avant-garde concept and free energy gimmicks. However, in the actual use of solar water heaters, it is impossible to be completely free. Due to the inability to work in rainy days and at night, solar water heaters need to be installed with electric auxiliary devices. With more and more urban haze weather, solar water heaters spend most of their time using electric energy in work, causing great energy waste. The advantages of heat pump are very clear