Reverse cycle air conditioning units extract heat from the outside air, even on mid-winter nights, and transfers it inside. A refrigerant is passed through an external coil, absorbing heat from the outside air. This refrigerant is then pumped through a compressor into a fan coil unit (or 'condenser') inside the home, releasing its heat into the room.
Up to three or more units of heat can be transferred for every unit of electricity used to run reverse cycle air conditioning.