External air is sucked inside the heat pump with the help of a fan. since the refrigerant in the evaporator is kept at a lower temperature than the surrounding atmosphere, it absorbs heat from the surroundings and evaporates. The compressor compresses the gaseous refrigerant and raises the pressure and temperature of the refrigerant.
The heated refrigerant runs through the condenser coil wrapped around the storage tank, transferring the heat to the water stored there and it cools and condensates.
The refrigerant then passes through an expansion valve where the pressure and temperature is reduced further for whole process to start again.