2nd February 2022. Air source heat pumps, explained

They’re the hottest new thing in green heating. But how do air source heat pumps actually work? Are they the right choice for every home? And how can they help the UK reach its Net Zero targets? Scroll down for all the answers.

Table of contents

What is an air source heat pump?  

This is what an air source heat pump looks like.

Air source heat pumps are a revolutionary new type of low-carbon heating.

They have clever technology that extracts the warmth from the air outside – even during the winter – and then uses it to keep things cosy and warm inside.

Why heat pumps are part of the green future

A heat pump works differently to a gas boiler. It uses the warmth found in the air outside of your home – plus a bit of electricity – to supply your home with all the heating and hot water it needs.

When it’s installed in an energy-efficient and well insulated house, an air source heat pump is more environmentally friendly than a gas-powered boiler.

That’s good news for your carbon footprint – and for the UK’s progress to Net Zero too.


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How do air source heat pumps work?

Air source heat pumps use the same kind of technology that keeps a fridge or freezer cool – but in reverse!

The pump pulls in air from outside, then uses it to heat a special refrigerant liquid. As it warms up, the liquid turns into gas.

This gas is compressed to increase its temperature – and provide lots of lovely heat for your home.

Once the gas cools down, it becomes liquid again and gets re-used at the start of the cycle.

The whole process only needs a little bit of electricity and even works when it’s as cold as -15°C during the winter.

The science sounds amazing, but it’s not new. It was first described by scientist Lord Kelvin back in 1852, believe it or not!


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The pros and cons of air source heat pumps

British Gas are installing air source heat pumps.

What's great:

  • Can heat your home more cost efficiently than a hot water boiler system
  • Much better for the environment – cutting your home’s CO2 emissions and improving local air quality
  • Affordable thanks to government grants (like the Renewable Heating Incentive worth up to £9k until March 2022)
  • Some models can be used with solar panels for a more self-sufficient system.

What can be a challenge:

  • Heat pumps are more expensive to buy than gas boilers, although government support is available
  • Some properties won’t have the right space, access or surroundings to install a heat pump
  • To get the best efficiency from heat pumps, your home will need to retain a lot of its heat through good insulation
  • Installing a heat pump might involve the cost and disruption of making changes to your house – including bigger central heating pipes and radiators.
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What are the different types of heat pump?

Air source heat pumps use air and electricity to extract heat.

There are two main types of heat pump. They work in a similar way, but they extract their heat from a different source – either the air or the ground.

It’s worth doing a bit of research before deciding which is best for you, but here are the main differences to think about.

Air source heat pumps

  • Cheaper and easier to install than ground source heat pumps
  • Higher running costs
  • The external heat pump unit is relatively small
  • Can work in temperatures as low as -15°C
  • Often require planning permission
  • Last for around 20 years.

Ground source heat pumps

  • More expensive and trickier to install than air source heat pumps
  • Lower running costs
  • Need to dig up large outdoor area (e.g. garden) to lay pipework
  • More efficient in lower temperatures
  • No need for planning permission
  • Last for around 20 years.

The other type you’ll sometimes hear about are hybrid heat pumps. These are air source or ground source heat pumps, but with a backup gas boiler that kicks in when extra heat is needed.

Whichever type you go for, you’ll be heating your home more sustainably than with a traditional gas boiler. In fact, if your electricity is zero carbon, you’ll be heating your home without creating any CO2 emissions at all.


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What government grants are available?

Replacing the nation’s gas boilers with greener, cleaner alternatives is a big part of the UK’s plans to reach Net Zero by 2050.

That’s why the government is offering financial incentives for people who make the switch to sustainable heating now.

Renewable Heating Incentive

This is the UK government’s current scheme, which is due to run until March 2022.

It gives you quarterly payments to help with the cost of going greener. The money you get depends on the amount of energy you save – and it could be as much as £9,000 over seven years.

Boiler Upgrade Scheme

This is the new scheme (previously known as the Clean Heat Grant) which will come into effect from April 2022.

It provides a one-off grant of up to £5,000 to help with the initial cost of upgrading from a fossil fuel boiler to a low-carbon alternative, like an air source heat pump.


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Is a heat pump right for you?

Here are some of the key things to think about before deciding to get an air source heat pump installed.

  • Is your current heating system past its best?
  • Do you have the exterior space next to your home that can easily fit a heat pump unit? 1
  • Is your home properly insulated to make the most of the heat pump – or is that something you’d consider investing in?

If the answer to these is yes, an air source heat pump could be an excellent low-carbon heating choice for your home.


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Ten heat pump myths, busted

There’s a lot in the news right now about heat pumps – and for good reason.

Their ability to heat your home without gas or oil means they’re a big part of the government’s Net Zero strategy. But with so many different opinions on exactly how they work and whether or not they’re worth the investment, it’s tricky to know what’s what.

But fear not. We’ve debunked some of the biggest heat pump myths out there to help you decide whether you’re ready to make the switch. It may well be easier than you think…

Heat pump myths

Myth #1: They don’t work in cold weather

This is one of the most common myths out there when it comes to heat pumps, and it’s simply not true.

Even when we’re wrapping up warm in the winter months, there’s still enough heat in the air and ground for heat pumps to absorb. In fact, the refrigerant in the heat pump can absorb heat in temperatures as low as -15°C. And because they compress the heat to a much higher temperature, it’ll still keep your home feeling cosy, no problem.

In the UK, it’s highly unlikely you’ll get temperatures that are too low for an air source heat pump. But for those who live in really cold countries, a ground source heat pump may be best, since they’re more efficient in freezing temperatures. That’s because the ground doesn’t really fall below 10°C, even in the harshest winters.

It might surprise you to learn that Sweden, with its frigid winters, is actually one of the biggest adopters of heat pumps in Europe.

Myth #2: Heat pumps are very noisy

Heat pumps often get a bad rep for being noisy. And while they’re by no means silent, if they’re installed properly and in the right place, they actually generate less noise than you might think. Air source heat pumps emit 50-60 decibels 2, which is only slightly higher than a low library whisper. Ground source heat pumps are even quieter as there’s no fan to worry about. And newer models are getting quieter and quieter, with thicker chassis and better fans.

If a heat pump does start making loud noises, it’s usually a sign that there’s something wrong.

Myth #3: Heat pumps always require planning permission

In most cases, you don’t need planning permission to install a heat pump as they fall under Permitted Development – but the requirements for this vary from country to country so it’s always important to check.

In the rare instance that they do need planning permission, it’s usually down to noise levels carrying across to neighbouring properties. That’s why it’s so important to get it installed by an expert. They’ll make sure it’s in the best place possible – i.e. away from any boundaries, to reduce the need for planning permission.

Myth #4: Heat pumps aren’t green because they use electricity

Many people think that because heat pumps use electricity, they can’t be green. But while heat pumps do need a small amount of electricity to get going, they’re much more efficient than traditional boilers, with the ability to generate 3.5kWh in heat for every 1kWh of electricity used. Plus, there’s no polluting gas or oil to worry about either.

To really up your heat pump’s green credentials, you can switch to an energy tariff that uses 100% renewable electricity. That way, you can rely on eco-friendly wind or solar power to power your system in the greenest way possible.

Myth #5: They need a lot of maintenance

Once they’re all set up, heat pumps actually require very little maintenance – often far less than a traditional heating system. Depending on the model, they should last at least 20 years 3, and there’s usually no need for replacement parts during their lifetime. A quick annual service should keep it working happily for many years to come.

And for extra reassurance, British Gas heat pumps come with a 5-year warranty and central heating cover for the first year.

Myth #6: They’re just too expensive

We’ll admit, heat pumps are pricier to buy and install than your standard boiler. But with a longer lifespan and less need for expensive repairs, they can actually work out more cost-effective over the years.

Plus, the government is incentivising people to go greener at home by switching from fossil fuel boilers to more sustainable alternatives. The Renewable Heating Incentive is available until March 2022, before the new Boiler Upgrade Scheme comes into effect in April 2022.

And if you buy one from us, you’ll get 7 years’ interest-free credit to help make things more affordable too.

The government has also announced its plans to invest in heat pump development to make sure they’re as cost effective to buy and run as a traditional boiler. Which could make them a lot more accessible to a lot more people. Find out more about the Heat and Buildings Strategy.

Myth #7: You need a huge garden for a heat pump

While ground source heat pumps do require a reasonable amount of outside space (around twice the footprint of your property), an air source heat pump is much more compact and can be mounted on an external wall like an air con unit. So, a huge garden (or even a garden at all!) really isn’t necessary.

In some cases, they can even be installed in apartment buildings. And as the technology develops, we’ll continue to see more and more heat pumps available for all sorts of property types.

Myth #8: Heat pumps only work in new builds

Since you will need a fairly well-insulated home for a heat pump to work properly, you could be forgiven for thinking they’re only for newer, more energy-efficient properties. But the good news is that heat pumps can work in the vast majority of British homes – even those that suffer a bit of heat loss in the colder months.

Of course, if you live in an older, draughtier house, you’ll need to get it properly insulated before you think about getting a heat pump, including loft and cavity wall insulation and double-glazing. But for most of us, this won’t take too much work – and it’ll significantly increase your home’s efficiency and drastically lower your heating bills to boot.

Myth #9: They only work with underfloor heating

Heat pumps are ideal for underfloor heating systems, but they work really well with radiators too.

Since they function best at a slightly lower temperature than traditional boilers, you may need to install a couple more radiators or replace them with slightly bigger ones to really reap the benefits.

But every home and heat pump is different, so our expert engineer will help you decide exactly what you need. And if your home’s already well insulated, you may not need to make any changes at all.

Myth #10: Everyone needs to get a heat pump

You might have seen news stories that gas boilers are going to be banned and will be replaced by heat pumps. Well, it's not quite like that – as this article explains. Yes, there's definitely a need to change the way we heat our homes – but heat pumps are only part of the long-term solution. Heat pumps are great for well insulated houses, but not all the UK's homes are suitable for this tech. The next generation of boilers will run on hydrogen gas – and they’ll be just as important for the future of UK heating. Instead of emitting CO2, they'll only emit super-eco H2O – aka water! You can find out about hydrogen boilers in this article. And by the way, the switch to 100% hydrogen is unlikely to happen until the mid-2040s, so there will be plenty of time for everyone to get ready for the change. Before then, the first phase will introduce a 20% hydrogen blend into the UK mains supply – and all boilers sold by British Gas today are hydrogen-blend ready, so you don’t need to worry about replacing them once the switch comes.

Pumped about heat pumps?

British Gas will be installing air source heat pumps in more and more areas of the UK. Here’s what you’ll get with us:

  • Expert engineer installation
  • Help with claiming government incentives
  • Five-year warranty
  • Easy ways to pay, including interest-free credit.

If you want to be one of the first to get this fantastic new technology, register your interest below. We’ll get back to you with next steps.


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Additional information

  1. Minimum space needed: Up to H: 1,565mm W: 1,100mm D: 450mm plus clearance around the pump.

  2. Source: Air-to-water heat pump system aroTHERM plus | Vaillant

  3. Source: Air source heat pumps | Centre for Sustainable Energy (cse.org.uk)