Imagine that you took an air conditioning unit and flipped it around so the hot coils were on the inside and the chilly coils were on the outside. Then you can have a heater. As it happens that this heater works very well. Rather than losing a fuel, what it's doing is "moving heating. " A heat pump is an air conditioner that contain a valve that lets it change between "air conditioner" and "heater. " In the event the valve is switched the best way, the heat pump acts as an air conditioner, and whether it is switched the other way it reverses the flow with the liquid inside the heat pump and acts like a heater. My websites: Heating and Air Conditioning Schools Help You to Get Ahead