What is a heat pump?

A heat pump is a device that can provide heating, cooling and hot water for residential, commercial and industrial use.

Despite the name, all heat pumps can provide both heating and cooling. They work well in nearly all types of climate.

Heat pumps take energy from the air, ground and water and turn it into heat or cool air.

This works due to what is known as the refrigeration cycle.

What is the refrigeration cycle?

In the refrigeration cycle, heat from a low-temperature energy source – such as the air, or water – is transported via a refrigerant fluid to a higher temperature energy sink – such as your home, or a building.

As the refrigerant is exposed to the energy source it evaporates, becoming a gas.

The gas is ‘compressed’ to raise the temperature further through mechanical energy – usually via an electric motor or a gas engine. Just like when you pump up a bicycle tyre and the pump gets warm!

This extra energy makes up about 20% of the total energy needed to run the heat pump. If green electricity is used, for example from solar or wind energy – then the heat pump uses 100% renewables and is carbon neutral.

What happens next?

Now the gas, which has become hot and highly pressurised, passes through a heat exchanger, called a condenser.

This heat exchanger allows the refrigerant to release the heat into the heating system for the house or building.

As a result, the refrigerant cools down, turning back from a gas into a liquid state.

The heat coming into the house or building can do so through an air system, like an air conditioning unit, or a water-based system like floor heating or radiators, known as ‘hydronic’. The indoor unit can also contain a hot water storage tank.

The condensed refrigerant then passes through a pressure-lowering device, known as the expansion valve. The now low-pressure liquid refrigerant can then begin the cycle again.

Read more about how heat pumps work
Read about the history of heat pumps


How do heat pumps work? An overview