A heat-pump system heats the cabin using the temperature difference between a refrigerant and the outside air, obtaining a heating effect other than consuming electricity, and making it possible to heat the car cabin with less power than conventionally.
Internal combustion engine vehicles re-use engine exhaust heat to provide the warm air for the functions of the heater. An EV, however, does not have this heat source to recycle and so, without a heat pump, needs to use its general power for cabin heating.
Conventional EV air-conditioning systems use an electrical heater, but since the use of the heater directly relates to power consumption, actual driving range can be significantly reduced compared to EVs which have a heat pump system.
A heat-pump is unique in that with one refrigerant circuit it can be used for both cooling and heating, with the heat from the outside air being transferable to the cabin just by the power consumption of the pump.