How it Works

A quick guide to explain how an Air Source Heat Pump works

The best way to understand how a heat pump works is to remember that temperature and the concept of hot or cold is subjective. With the coldest possible temperature being absolute zero at -273°C, your average fridge at 5°C could be perceived as hot! Heat is energy, the more intense the energy the higher the temperature produced. What air source heat pumps do is absorb energy from the outside air and intensify it to increase its temperature. The hot water produced is then used to heat radiators, underfloor heating systems and hot water cylinders in your property. It can extract and intensify the heat from the air outside even when the temperature is as low as -20°C.

Diagram to show how an Air Source Heat Pump Works

The Fan

A fan passes ambient air over the evaporator. The refrigerant boils and evaporates at low temperatures.


Vapour is then channelled into an electric compressor, increasing the pressure and temperature of the vapour.

Warm Vapour

Warm, high pressure vapour then enters the heat exchanger producing heat for water or heating system.

Condensed Vapour

Condensed vapour returns to liquid, passes through the expansion valve, reducing pressure and temperature. The cycle repeats.

From Cold to Warm

An air source heat pump works by absorbing heat from the air into a fluid (commonly known as a refrigerant) that travels through a looped system of pipes. This process increases the temperature of the liquid until it transforms into a gas (the refrigerant effectively boils).

This gas then passes through the system towards a compressor, which increases the temperature even further (compressing a relatively large volume of gas through a relatively small hole creates heat – if you put your finger over the end of a bicycle pump and depress the plunger, it will burn your finger, please don’t try this, it will hurt!)

As the gas heats your home’s central heating system, it starts to cool and transforms back to a liquid (condenses). This liquid is pumped back outside into the looped pipe system, which restarts the process as the liquid begins to absorb more heat from the air.

Beautifully Simple

This process continues until its warm enough to provide you with central heating and your hot water. Any leftover heat can be stored in a hot water cylinder. The system and the technology are beautifully simple, efficient, safe and well proven – it simply works!

There is no need for a naked flame or combustible gases in your home, no need to have an oil tank in your garden or for big orange cylinders outside your window.

Air source heat pumps (also known as ASHPs) are a low carbon heating system that use the ambient air to heat up your home. They can be used for both hot water and space (room) heating. For more information / enquiries, please

Contact Us

Like to know more?

If you’d like more information on air source heat pumps, would like to make an enquiry or just ask a question. Please contact Wright Renewable Heating in Worksop, Nottinghhamshire today. We’re on hand and ready to help. Alternatively, please check out some of our related air source heat pump material and documentation from the quick links below