Around and around again

A loop that never stops

Cooled to about 7 °C, the refrigerant flows back into the indoor unit and takes in the room’s heat again. It boils in the indoor unit, gets squeezed in the compressor, cools into a liquid in the outdoor unit, and passes through the tiny opening of the expansion valve to get cold again, over and over without stopping. In this example, the air conditioner moves about 4.1 units of heat out of the room for every 1 unit of electricity.

Why?An electric heater makes heat directly from electricity, so 1 unit of electricity gives 1 unit of heat. An air conditioner does not make heat; it only moves it, so it can move several times more heat than the electricity it uses.

Learn moreThe hotter it is outdoors, the hotter the refrigerant must be squeezed, so moving the same heat takes more electricity. Run the refrigerant the other way through the same machine and it becomes a heater (a heat pump) that moves outdoor heat into the room. The ratio of heat moved to electricity used is called the coefficient of performance (COP).

Heat moved per 1 unit of electricity

4.1

calculated from R-32 property tables (CoolProp) · example: room 27 °C, outdoors 35 °C