Understand how heat pumps work with this simple guide for UK homeowners.
How Does a Heat Pump Work? A Simple Guide
How a heat pump works
A heat pump works in a similar way to a fridge — but in reverse. A fridge removes heat from inside the appliance and releases it outside. An air source heat pump takes heat energy from the outside air and transfers it into your home to provide heating and hot water. Even when outdoor temperatures are low, there is still heat energy available in the air, allowing modern heat pumps to operate in cold weather.
The four stages
Absorb: Outside air passes over a refrigerant with a very low boiling point. The refrigerant absorbs heat from the air and evaporates, even when outdoor temperatures are only a few degrees above freezing.
Compress: The refrigerant vapour is compressed by the heat pump’s compressor, increasing its pressure and raising its temperature significantly.
Transfer: The hot refrigerant passes through a heat exchanger, transferring the captured heat into the home’s central heating and hot water system.
Expand: The refrigerant passes through an expansion valve, reducing its pressure and temperature so it can absorb heat from the outside air again and repeat the cycle.
Why heat pumps are more efficient than electric heaters
A conventional electric heater uses 1 unit of electricity to produce roughly 1 unit of heat. A heat pump works differently: it uses electricity to move heat from the outside air into your home, so 1 unit of electricity can produce several units of heat. This efficiency is measured using the Coefficient of Performance (CoP). For example, a heat pump with a CoP of 3 produces around 3 units of heat for every 1 unit of electricity used under the stated operating conditions. Actual efficiency varies depending on outdoor temperature, flow temperature, system design and how the heat pump is operated.
