The process begins with a cold, low-pressure refrigerant circulating through an evaporator coil. This coil is exposed to the outside air (in air source systems) or buried underground (in ground source systems). Even at sub-zero temperatures, the refrigerant absorbs ambient heat, causing it to evaporate into a gas.
> Think of it like a sponge soaking up heat from the environment—even when it feels cold to us.
The now gaseous refrigerant enters a compressor, which significantly increases its pressure and temperature. This is where the magic happens: compressing the gas concentrates the heat energy, raising its temperature to a level suitable for heating your home.
> This step requires electricity, but the energy output is 3–4 times greater than the input.
The hot, high-pressure gas flows into a condenser coil inside your home. Here, it releases its heat into the central heating system—warming radiators, underfloor heating, or a hot water cylinder. As the refrigerant gives up its heat, it condenses back into a liquid.
> This is the point where your home actually feels the benefit—warm rooms, hot water, and comfort.
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Before the refrigerant can absorb more heat, it passes through an expansion valve. This reduces its pressure and temperature, turning it back into a cold liquid. It’s now ready to re-enter the evaporator and start the cycle again.
This closed-loop cycle runs continuously, adjusting output based on your home’s demand. Because it moves heat rather than generating it, a heat pump can deliver 300–400% efficiency—meaning for every 1kWh of electricity used, you get 3–4kWh of heat.
Heat pumps are ideal for:
They’re especially effective in well-insulated homes and can be paired with solar panels for even greater savings.