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Thinking about switching from your gas boiler but unsure how a heat pump keeps your home warm? We break down exactly how they work, which type might suit your home and what you need to know before making the switch.
Heat pumps are changing how UK homes stay warm. They pull heat from the outside air or ground—even in cold weather—and move it inside your home. Think of them like a fridge working in reverse. While a traditional boiler burns fuel to create heat, a heat pump simply transfers existing heat, using much less energy in the process.
How do heat pumps work? A step-by-step guide
Your heat pump captures warmth from outside and moves it indoors using a refrigerant. The process runs in a continuous loop to heat your home.
- The unit's fan pulls outdoor air over a heat exchanger filled with cold refrigerant liquid
- This refrigerant absorbs heat from the air and turns into gas
- A compressor squeezes the gas, raising its temperature significantly
- The hot gas flows to your indoor unit where it heats your home's water
- As the refrigerant cools, it turns back to liquid
- The process starts again, running steadily to maintain your chosen temperature
A heat pump captures heat from outside to warm your home. This clever trick works even in cold weather because the refrigerant gets cold enough to absorb heat from chilly air.
What are the different types of heat pumps?
Most UK homes choose between three main types of heat pump. Each works differently and comes with its own benefits, so picking the right one depends on your home's setup and your budget.
How does an air-source heat pump work?
These look like big air conditioning units mounted on your outside wall. They pull heat from the air and work well in the UK's mild climate. Most homes pick these because they cost less to install and don't need much space.
How does a ground-source heat pump work?
Ground-source systems use pipes buried in your garden to capture heat from the soil. The ground stays at a steady temperature all year, which makes these systems very reliable. You'll need a decent-sized garden, but they often cost less to run than air-source pumps.
How does a hybrid heat pump work?
Hybrid systems team up a heat pump with your existing gas boiler. The heat pump handles most of your heating, while the boiler helps during very cold spells or when you need lots of hot water quickly. It's a good middle ground if you don’t want to make the full switch to a heat pump.
Can you connect a heat pump to an existing heating system?
Switching to a heat pump doesn't always mean replacing everything. Your current setup might work fine with some adjustments, but you'll need to check a few key elements before making the change.
Do heat pumps work with radiators?
Your existing radiators can work with a heat pump, but it’s dependent on the size. Heat pumps warm water to lower temperatures than boilers, so you might need bigger radiators to heat rooms properly. Some homes need double the radiator size, while others work fine with what they have. Many people add smart radiator valves for better control.
Can I replace my boiler with a heat pump?
Most homes can switch from a boiler to a heat pump, but you'll need good insulation first. Your electricity supply might need upgrading to handle the extra load. You'll also need enough space outside for the unit—usually a clear area about the size of a washing machine. Planning permission rules vary, so check with your local council.
Can you use a heat pump with a hot water heating system?
Heat pumps heat water differently from boilers. They work more slowly and keep water at lower temperatures, typically around 50°C instead of 60°C or higher. You'll probably need a bigger hot water tank, and some homes add an immersion heater for backup. The good news is that modern heat pumps can provide all your hot water once set up properly.
The role of heat pumps in reaching net zero
A heat pump cuts your home's carbon footprint by up to 65% compared to gas heating. The UK aims to install 600,000 heat pumps yearly by 2028, replacing fossil fuel boilers as part of its path to net zero. While a heat pump runs on electricity, which still creates some emissions, the power grid becomes greener each year as more renewable energy comes online.
Electric heat pumps play a central role in cutting emissions from homes, which cause about 16% of the UK's carbon output. Gas boilers pump out nearly two tonnes of carbon each year in a typical home. In contrast, heat pumps create just one-third of those emissions today, a figure that keeps dropping as the electricity supply becomes cleaner.
The government offers grants up to £7,500 to help homes switch to heat pumps, making them more affordable. Over 40,000 heat pumps went into UK homes between January and October 2024, which shows growing confidence in the technology. With proper installation and good insulation, they provide reliable warmth while helping tackle climate change.
Heat Pumps FAQs
The size of heat pump you need will depend on several factors, including:
- The size of your home: The larger the home, the larger the heat pump will need to be to meet the heating demand.
- Insulation levels: A well-insulated home will need a smaller heat pump than a poorly insulated home.
- Size of household: A home with more people living in it will need a larger heat pump to meet the heating demand.
- Climate: The climate where you live will also play a role in determining the size of the heat pump you’ll need. In colder climates, a larger heat pump will be needed to keep the home warm.
- Type of heat pump: Different types of heat pumps have different efficiencies. Some are better at handling extreme temperatures.
A qualified professional, such as an MCS-accredited installer, will be able to determine the size of the heat pump you need by conducting a heat load calculation. This calculation takes into account all of the factors mentioned above and is used to determine the heating demand of your home.
Just one heat pump should be able to supply enough heat to keep almost any home warm. Heat pumps come in different sizes, so you’ll simply need one suitably sized heat pump for your home rather than several.
A heat pump has the potential to save you money in the long term as they’re more energy efficient than traditional heating systems.
However, this will depend on various factors, including the cost of electricity in relation to gas - the smaller the difference, the more cost-effective a heat pump will be in comparison to a gas boiler due to its increased energy-to-heat efficiency.
Other things to factor in are your energy usage, the size and efficiency of the heat pump, and the costs of installation and any upgrades (e.g. hot water tank, piping and radiators).
And although not a saving, it’s worth bearing in mind that a heat pump can add value to your home as well as being better for the environment.
As of March 2024, heat pumps could save an average household with a gas boiler around £234 per year.3
Yes. Heat pumps can work in cold weather, even down to -20 Celsius! But their efficiency may decrease as the temperature drops.
The lifespan of a heat pump will vary depending on the type and brand. The average heat pump should be able to last for around 15-20 years.
Think of it like a reverse refrigerator. Instead of pushing heat out to keep things cool, a heat pump captures warmth from the outside air or ground and moves it into your home to keep you warm.
Modern heat pumps work well even when it's -15°C outside. They become less efficient in extreme cold, but UK winters rarely get cold enough to stop them working. Most units keep heating your home effectively down to -20°C.
Heat pumps work best when they run steadily at a low level, unlike boilers that switch on and off. This steady operation uses less energy and keeps your home at a more stable temperature throughout the day.
Keeping your heat pump running at a steady temperature saves more energy than switching it on and off. Set it to a comfortable level and let it maintain that temperature - it's more efficient than making big temperature changes.
Heat pumps easily maintain normal living temperatures around 19 to 21°C. They work best keeping steady temperatures rather than making quick, big changes like gas boilers do.
Your home warms gradually with a heat pump, typically taking two to three hours to reach temperature. Unlike gas boilers, they don't provide instant heat but maintain warmth more efficiently once up to temperature.
A heat pump typically uses one unit of electricity to produce three to four units of heat energy. For a standard UK home, this usually means lower running costs than a gas boiler, especially with good insulation.
Heat pumps may have started to gain popularity in the UK only recently, but they’re already a significant part of the energy infrastructure in many parts of the world. As a result, there are lots of manufacturers of heat pumps.
Brands that sell heat pumps in the UK include:
- Ecoforest
- Kensa
- LG
- Mitsubishi
- Nibe
- Panasonic
- Samsung
- Stiebel-Eltron
- Vaillant
- Viessmann
- Worcester-Bosch
These brands offer a variety of heat pump models and types, including ground-source heat pumps, air-to-air heat pumps, and air-to-water heat pumps.
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