What is a heat pump?

Heat pumps are becoming more and more popular as a way to heat UK homes. And the government’s offering the £7,500 Boiler Upgrade Scheme grant to households installing one.

They’re still relatively new when it comes to heating in the UK, although millions have been installed across Europe. So how do heat pumps work? And what are the differences between various types of heat pump?

What is a heat pump?

A heat pump is a low-carbon, efficient way to heat your home. Heat pumps use electricity to absorb heat from the air outside or the ground to heat your home. They work like a fridge or an air-conditioner in reverse. There are various different types of heat pump, but they all work in the same way. They follow a refrigeration cycle to absorb heat and warm up your home.

What are the different types of heat pumps?

There are 2 main types of heat pump: air source heat pumps and ground source heat pumps. Both have advantages and disadvantages, depending on the home they’re installed in and what they’re being used for.

The most common type are air source heat pumps, which use heat from the outside to heat your home. They compress a fluid to make the captured air hot enough to heat your home and give you hot water. There are 2 types of air source heat pump.

Air-to-water heat pumps

Air-to-water heat pumps distribute heat by pumping liquid through pipes and radiators or underfloor heating pipes. They’re the most common type of heat pump used in the UK. They’re around 4 times more efficient than most gas boilers. And use less carbon as they’re powered by electricity rather than gas.

Interested in getting an air-to-water heat pump in your home? You can now get one installed through OVO and our exclusive partnership with Heat Geek. You’ll also unlock our free add-on, Heat Pump Plus, which gives you a better electricity rate for powering your heat pump. It means you can save up to £375 a year on your heating bills compared to a gas boiler.¹

Find out more and get a heat pump estimate.

1. The air source heat pump takes in air from outside to heat a liquid refrigerant. This turns it into a gas.
2. Using electricity, the heat pump compresses this gas to increase its temperature. This heat is transferred into your home, and the gas condenses back to a liquid again.
3. Stored hot water can be used for showers, baths and taps.
4. Heat is sent to your radiators or underfloor heating. It can also be used to heat water in a hot water cylinder.

Air-to-air heat pumps

Air-to-air heat pumps are like air conditioning. They take heat from the outside air and transfer it into your home through a network of fans. They’re typically used to cool down buildings, but can also be used for heating. The main disadvantage of this system is that it can’t be used to heat water, so you need a separate way to do this. These heat pumps are often installed in Europe, where temperatures are hotter and air conditioning is more important.

Ground source heat pumps

Ground source heat pumps work in a similar way to air source heat pumps. But to heat your home and water they pull heat from the ground, rather than the air.

A fluid moving through pipes buried in the ground absorbs the heat from the ground. The fluid is then compressed to raise its temperature, and a heat exchanger transfers the heat into your home.

This system involves laying pipes underground, and needs a lot of space in your garden or outdoor area. So it's usually more expensive to install than an air source heat pump. It can be more disruptive, as your engineer will likely need to dig trenches or a borehole in your garden to install the pipes.

Why an air-to-water heat pump is the best option for most homes

Heat pumps are low maintenance, low carbon systems compared to the systems they replace. That’s because they heat homes using electricity rather than gas.

For most homes, an air source heat pump is a more practical, cost-efficient option than a ground source heat pump.

Air-to-water heat pumps can heat up your radiators, underfloor heating, and water. Although air-to-air heat pumps can be used for both heating and cooling your home, they can’t directly heat up water. So you’ll need another heat source for your hot water, which could cost you more in the long run.