Air Source Heat Pump Installation Explained

man installing a heat pump

Installing an air source heat pump usually takes one to five days

It can save you £141 per year, on average

The installation process requires electrical and plumbing expertise


Getting an air source heat pump is a great decision.

It can help you to save £141 per year on your energy bills, and cut your annual carbon footprint by more than two tonnes of CO2.

These machines are effective, reliable, and futureproof – unlike gas boilers, which you won’t be able to buy in the near future.

And with the Boiler Upgrade Scheme offering £5,000 to homeowners who want to get an air source heat pump from April 2022 to April 2025, now’s the time to act.

Here’s everything you need to know about how installers will set you up with a new, top-quality air source heat pump.

man installing a heat pump

What is an air source heat pump?

An air source heat pump is a renewable heating system that uses electricity to take warmth from the air outside and uses it to supply you with heat and hot water.

The machine absorbs the heat into a fluid, compresses this fluid to increase its temperature, then sends the resulting hot water to your radiators and underfloor heating system.

When you’re not using your heating system, you can store the excess fluid in a hot water cylinder.

And because the sun has already partly heated the air, an air source heat pump is able to produce more units of heat than the units of electricity it uses, making it an extremely efficient source of green energy.

For more details, read our What Is an Air Source Heat Pump? article, which explores this subject fully.

infographic of how an air source heat pump works

How is an air source heat pump installed?

The air source heat pump installation process is painless, provided you hire a professional company with installers who are qualified electricians and plumbers.

Don’t install an air source heat pump yourself, unless you’re certified in electrical and plumbing work. Any savings you make initially will be eradicated when the system breaks.

We’ve laid out all the steps below that will take you towards the destination of a new, functioning air source heat pump, so you know what your installers are doing.

1. Inspection

The best first step is to ask a company that installs heat pumps to send a heating engineer to assess your home and decide what size of air source heat pump you need.

Some companies will perform this assessment for free, but it usually costs around £150.

This payment is often removed if you choose the assessing company to carry out the heat pump installation, but either way, it’s incredibly useful to know how to save money on your energy bills.

Over the course of an hour (at most), the engineer will measure how big your home is, the number of rooms you need to heat, your insulation levels, and the size of your radiators.

They’ll also take into account if you have underfloor heating, which is an excellent way to spread warmth through your home when you have a heat pump.

All of these considerations will help them work out how much heat is regularly lost from your home. The more heat that’s lost, the bigger the heat pump you’ll need.

To reduce your heat losses and make your home more suitable for a heat pump, the engineer may recommend you get better insulation, bigger radiators, or underfloor heating. They may be able to carry out these improvements for you while installing the heat pump.

Fortunately, many radiators in UK homes are already larger than they need to be for gas heating, which may be perfect for your new heat pump. Only one-third of homes will need bigger radiators – and your engineer will be able to tell you if you’re among them.

2. The outdoor unit

The actual heat pump will then be installed just outside your home, next to one of the external walls.

The heat pump needs easy access to the air, so your installer will choose a spot where nothing blocks it in, then either bolt it to a flat concrete base, or use brackets to attach it to the wall.

This ensures that come rain, hail, or snow, your heat pump will remain steadfast in its position.

3. The indoor unit

The installers will then move inside to set up the other main part of this process: your hot water cylinder.

This is the wonderful machine that will hold onto all the hot water you don’t need straight away, allowing you to make full use of all the warmth your heat pump produces.

Your installer will recommend the right size for your home, but just so you know, the average three-bedroom house requires a 200-litre cylinder.

If you have two bedrooms, you can probably settle for a 150-litre unit, while houses with five bedrooms or more will likely need at least 300 litres of capacity.

If you already have a hot water cylinder, it probably won’t be suitable for a heat pump system, as the coil is usually too small to reheat the water as quickly as it should.

4. Connections

Then it’s time to link everything up.

Your installer will connect the external heat pump to the internal hot water cylinder via a control wire, a refrigerant hose, and a condensate drain hose.

They’ll usually have to drill a hole in the wall to feed these through.

The installer will then connect the hot water cylinder to your radiators, and to your underfloor heating if you have it, by installing some pipework.

At some point during this process, your old heating system will need to be disconnected, but the installer will warn you about this in advance, and let you know how long it’ll take. It’s usually a matter of hours.

This part of the installation in particular will make you thankful that you hired installers who know their way around electrical units and plumbing.

person installing a heat pump

How much does air source heat pump installation cost?

Installing an air source heat pump costs around £150 per hour. With an average installation time of three days, this generally works out to £3,000 overall. That means that the total price of buying and installing an air source heat pump is typically £10,000.

Make sure you get multiple quotes before moving ahead with an installer, to avoid paying well over the odds.

But remember: unless you’re a certified plumber and electrician, don’t do it yourself. The price of installing a heat pump to an inferior standard is likely to be much, much higher in the long term.

Is there any maintenance required afterwards?

Thankfully, air source heat pump maintenance is a relatively simple task. Just make sure to keep the external unit clean and free of debris, so the airflow doesn’t get obstructed.

You can do this by replacing the filters every one to two months, wiping down the coils and fan blades, and using a soft-bristled brush to clean the registers.

Refill the antifreeze once per year, de-ice the machine in winter, and make sure grass and other plants don’t encroach on the heat pump’s area.

A professional service is also a good idea, but it doesn’t need to be too regular. One every two to three years should suffice.

With very little upkeep, an air source heat pump can last for at least 20 years – much longer than a gas boiler, which typically needs replacing after 10 to 15 years.

How many heat pump installers are there in the UK?

There are currently 1,200 heat pump installers in the UK.

This falls well short of the number needed if the government is to meet its target of 600,000 heat pumps installed per year by 2028 – especially when compared with the UK’s 130,000 certified gas boiler installers.

With its 2028 goal in mind, the government now offers free or subsidised training to tradespeople who want to learn how to install heat pumps, under the BEIS Skills Training Competition scheme.

With 18 training providers across the country offering this course, we should see a massive increase in the number of heat pump installers over the next few years.

Next steps

You’re now fully prepared to save money and energy with your new heat pump.

The next step is to ask for a heat loss assessment of your property, make any necessary improvements, and then buy the best heat pump for you.

And with the government’s Boiler Upgrade Scheme (starting April 2022), you could save £3,900 over the machine’s lifetime – and reduce your emissions by more than two tonnes of CO2 per year.

That’s one-third of your carbon footprint, gone. Lovely.

Josh Jackman Senior Writer

Josh has written about eco-friendly home improvements and climate change for the past three years. His work has featured on the front page of the Financial Times; he’s been interviewed by BBC Radio; and he was the resident expert in BT’s smart home tech initiative.

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