If air-conditioning means cooling to you, then you should think again. A modern air-conditioning system is completely reversible, i.e. it heats as well as cools. It is actually a heat pump and therefore it is a very economical way of heating your home, with the added bonus than in the summer it works the other way and thus cools it to a comfortable level. The ‘airconditioner’ is an air-air heat pump. It is called that because its heat source is the ambient air in the vicinity of the outside unit. The heat energy is absorbed from the air by the refrigerant fluid contained in the unit’s pipe work. This energy is carried by the fluid to the unit inside the home where it is released into the room.

Both units have fans in order to draw in the ambient air and at the other end to blow the heated air gently around the room. The summer process is the exact reverse, so cooled air is blown into the room and the heat from inside the house is dispersed outside. Air-air heat pumps are not limited to the simple one outside unit and one inside unit. In a multi-split system, one outside can supply up to seven inside units, which means the whole house can be heated/cooled in the same manner.

The reason for a heat pump’s economy is that it increases by three times the amount of heat energy returned against the energy consumed in its operation. In effect, for every one kilowatt of electricity used to run the unit, you get three kilowatts of heat out of it. This efficiency is one of the reasons why the French government is offering a 50% tax credit on the cost of an installed heat pump, as long as the installation meets certain criteria.