The quickest way for people who know about air-conditioners and don't know about heat pumps is to consider what would happen if you put your air-conditioner the

The quickest way for people who know about air-conditioners and don't know about heat pumps is to consider what would happen if you put your air-conditioner the wrong way around in the wall. Instead of lovely cold air coming in and waste hot air going outside, the waste hot air would be heating the house and the cold air would be going outside. There is no such division of things into air-conditioners and heat-pumps. Air conditioners ARE heat pumps. In some parts of the world dual-direction heat-pumps are (or rather were) called 'Reverse-Cycle Air Conditioners' meaning they they could be switched from cool-inside/warm-outside to warm-inside/cool-outside. Another thing to learn is the difference between temperature and heat. It's very similar to the difference between voltage and kilowatt-hours. And 'cold' or 'freezing' are just labels. A litre of water at 70 degrees C will give the same amount of heat going to 40 degrees C as a litre of water going from 40 degrees C to 10 degrees C. Similarly 100 cubic metres of 'freezing' air at zero degrees C going to -10 degrees C can give as much heat as 100 cubic metres of air going from 30 degrees C to 20 degrees C. That 'freezing' air at 0 degrees C is actually at 273 degrees Kelvin. It has A LOT of heat in it.