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Heat pumps are becoming more and more popular as a way to heat UK homes. And the UK and Scottish governments are both offering a £7,500 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 an energy-efficient way to heat (and sometimes cool) your home. Instead of burning gas like a boiler, it uses electricity to move heat from the air outside or the ground into your home. It works a bit like a fridge – but in reverse.
Heat pumps are low-carbon and can help cut your energy bills. Whether it’s air source or ground source, they all work using the same basic process: absorb heat, compress it, and release it indoors to warm your space.
What are the different types of heat pumps for homes?
There are two main types of heat pumps commonly used in UK homes: air source heat pumps and ground source heat pumps. Both systems provide energy-efficient heating, but they extract heat from different sources.
Air source heat pumps absorb heat from the air outside your home.
Ground source heat pumps extract heat from the ground via buried pipes.
Each type has its own benefits, costs, and installation requirements, depending on your property type, insulation, and available outdoor space.
How is a heat pump installed in your home?
Installing a heat pump typically takes a few days and involves both indoor and outdoor work. For air source heat pumps, an outdoor unit is mounted near your home, and indoor piping connects to radiators or underfloor heating. Ground source systems require digging in your garden – either trenches or a borehole. A certified installer will assess your property and help design the best system for your needs.
Air source heat pumps: An outdoor unit is installed near your property to draw in air. Pipes are run indoors to connect the system to your radiators, underfloor heating, and hot water cylinder.
Ground source heat pumps: These require more extensive groundwork. Pipes are buried in horizontal trenches or a vertical borehole to extract heat from the ground.
What is an air to water source heat pump?
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 boilers1. And they use less carbon as they’re powered by electricity rather than gas.
How do air source heat pumps work?
An air source heat pump works by absorbing heat from the outside air and transferring it into your home using a refrigeration cycle. Here's how the process works:
Air is drawn in from outside to heat a liquid refrigerant, which then evaporates into a gas.
The system compresses the gas using electricity, increasing its temperature.
This heat is transferred into your home via a heat exchanger.
The gas condenses back into a liquid and the cycle repeats.
The heat produced is used to warm your radiators, underfloor heating, and hot water cylinder. Stored hot water can then be used for showers, baths, and taps.
What is an air-to-air heat pump and how does it work?
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 Europe₂, where temperatures are hotter and air conditioning is more important.
What is a ground source heat pump and how does it work?
A ground source heat pump (also known as a geothermal heat pump) provides heating and hot water by extracting natural heat from the ground. It works in a similar way to an air source heat pump, but instead of drawing heat from the air, it uses the stable underground temperature just below the surface.
How they work
A special fluid circulates through a network of pipes buried underground (in trenches or a vertical borehole).
The fluid absorbs heat from the ground, even during winter.
The heat pump compresses the fluid to raise its temperature.
A heat exchanger transfers the heat into your home’s central heating and hot water system.
Installation and considerations
Ground source systems are highly efficient and low-carbon but require more outdoor space and are usually more expensive to install than air source heat pumps. Your installer may need to dig up your garden or outdoor area to lay the ground loop or drill a borehole.
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 more practical and cost-efficient than a ground source heat pump.
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. Air-to-water heat pumps, however, can heat up your radiators, underfloor heating, and water.
How long does a heat pump last and what maintenance does it need?
A well-maintained heat pump system typically lasts 15 to 20 years, with some lasting even longer depending on usage and care. Heat pumps are known for their reliability and low maintenance requirements compared to traditional gas boilers.
Heat pump maintenance includes:
Annual servicing by a qualified technician
Checking and topping up refrigerant levels
Cleaning or replacing filters
Inspecting the system for efficiency and performance
With regular servicing, your heat pump can operate efficiently for many years and help reduce both your carbon footprint and energy bills.
Important Information
1. Source: How a heat pump works - International Energy Agency.