How Does a Heat Pump Work?

The refrigerant cycle

A heat pump moves heat with refrigerant, a fluid that absorbs and releases heat as it changes between liquid and gas. The compressor pumps it around a loop between two coils, one outdoors and one indoors. As the refrigerant evaporates it soaks up heat; as it condenses it gives heat off. Move that loop in one direction and you carry heat inside; reverse it and you carry heat outside.

Heating mode

In winter, the outdoor coil acts as the absorber. Even in cold air there is heat to capture, so the refrigerant pulls heat from outside, the compressor raises its temperature, and the indoor coil releases that heat into your home.

Cooling mode

In summer, the reversing valve flips the flow. Now the indoor coil absorbs heat from your home and the outdoor coil dumps it outside, exactly like a regular air conditioner.

The main parts

Because the system moves heat rather than burning fuel, it can deliver more heat energy than the electricity it uses, which is what makes heat pumps efficient.