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Combi Boiler Installation: Costs & Guide (2024)

Nick Geary
By: Nick Geary
Updated: 14th February 2024

New combi boiler installation

Combi boilers are hugely popular across the UK.

They don't take up much space and there's no need for any additional tanks or cylinders. This can mean that a new combi boiler installation can be finished in 1-2 days (although certain factors can cause installation delays).

So, if you're looking to maximise the space in your home and join the millions of other homeowners in the UK who enjoy all the benefits of a new combi boiler, here's everything you need to know about the installation process and costs.

However, if you’ve already made up your mind on what type of boiler you want and just want to get your new combi boiler installation done as soon as possible, we're here to help you get started in no time. Instead of wasting hours of your precious time researching local installers, let us put you in touch with up to 3 Gas Safe registered combi boiler installers. 

Simply click below, fill in our short form, and sit back and relax while trusted professionals vetted by us get back to you with tailormade quotes for a new combi boiler installation. You can then compare figures to find the installer that best suits your needs and secure the best deal for your home. Click below to get started now!

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How the combi boiler installation works

combi boiler replacement

Before the installation

What is shown in the combi boiler installation diagram above is the process of having the new boiler installed. However, before that, you will want to compare boiler quotes from at least 3 different engineers to secure the best deal on your installation. 

A quote involves a Gas Safe registered engineer visiting your home to take a look at the work involved. They'll work out what size boiler you need, and help you answer the question: "Do I need new pipes for a combi boiler?" Then, they will offer you a complete quote. By arranging for more than one engineer to give you a quote, you'll have a better chance of finding the most competitive price.

It’s then up to you to choose the best quote and organise a day for the installation to take place. Additionally, if you're wondering: "Can a plumber install a combi boiler?" then the answer is yes. As long as they're Gas Safe registered. To make sure that your new combi boiler installation is as safe as possible, make sure to check the qualifications of the professional you choose to work with. 

Installation day

When they arrive, the engineer will cover up the carpets and surfaces where they will be working. So they don’t damage or dirty any of your belongings while they are fitting a combi boiler in your home. 

The first day should involve a powerflush. This will clear out any debris (rust, limescale and sludge) from the heating system. Once cleared, the hot water will be able to flow through your radiators without getting blocked - making them far more efficient. This in itself can take a whole day.

There's a chance that a like-for-like combi replacement could be done in a day. But it would be a long day. From our own experience, most boiler replacements will take at least a couple of days. While the longest jobs (moving a boiler or a full central heating system replacement) can take four days or more. This will also influence the central heating installation cost.

Once the boiler’s been fitted

After the installation of your new boiler, the engineer will show you how to use the controls and answer any questions you may have. 

They will also fill out the Benchmark Checklist found at the back of the boiler manual. The installer will also register the installation with the manufacturer to start the warranty. You’ll also get a Building Regulations Certificate through the post. Make sure you hold onto all of this paperwork because you’ll need it.

As part of their service, the installer will also be removing your old boiler from your home. Once all the checks have been done and the installer confirms that everything runs smoothly and safely, you are ready to start using your new combi boiler.

New combi boiler installation costs

Combi boiler prices range from as little as £500 up to £3,000 depending on the brand, output, and fuel type (combi oil boilers tend to be more expensive than combi gas boilers). The tables below give some averages for combi boiler costs for some of the leading brands (excluding installation costs).

Gas combi boiler prices

Manufacturer Average price (without installation)
Glow-worm £525 – £915
Ideal £850 – £1,400
Baxi £610 – £1,300
Worcester Bosch £730 – £2,500
Vaillant £900 – £1,700

Oil combi boiler prices

Manufacturer Average price (without installation)
Firebird £2,150 – £2,600
Grant £2,200 – £3,100
Worcester Bosch £2,400 – £2,800

These prices are for the supply of the combi boiler only. To get the boiler installed you’ll need to pay a Gas Safe registered engineer (or OFTEC registered engineer in the case of oil boilers) for their labour.

Finding a trustworthy heating engineer while not overspending on installation costs can be extremely difficult to do on your own. After hours of tedious research, you might still not have found the right installer for the job, nor the best deal for your home. This could cost you thousands, as well as lots of time and energy.  

If you would like to contact a registered engineer in no time and find the best price for your new combi boiler, simply use our quick free service. By filling in our short form, you can receive up to 3 quotes for a brand-new boiler from trustworthy professionals in your area. Then, just compare quotes to choose a reliable installer to work with and to find the best deal for your new combi boiler.

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A new combi boiler installation will also involve labour costs, expenses for any additional parts or pipework required, as well as VAT. When you replace a boiler, it’s common practice for the engineer to carry out a powerflush on your heating system. Many heating companies will include this service as standard within their quote, but sometimes there may be an extra charge for this.

Other work that could add to the cost of a new combi boiler installation include moving a boiler to a new location, replacing or relocating a gas pipe, adding a condensate pipe, removing expansion tanks and/or hot water cylinders, and any structural changes to the home such as bricking up an old flue hole.

Here are some average industry costs for some scenarios to consider:

Type of installation Average cost Time
Combi to combi (same location) £1,500 – £2,700 1-2 days
Combi to combi (different location) £1,500 – £3,000 2 days
System to combi £1,500 – £3,000 2-3 days
Conventional to combi £2,500 – £4,500 2.5 days
New central heating system with combi £2,000 – £5,000 4+ days

Replacing a combi with a combi

Replacing a combi with a combi

The costs for this kind of boiler swap can range anywhere from £1,500 to £2,700, depending on your situation. Your expenses will be higher or lower depending on the size of your boiler and whether you want to relocate your new boiler within your home. 

If you are considering changing your boiler, the easiest way to go about it is to replace a combi boiler with a new combi boiler. Because it requires no or minimal changes to the pipework and because no additional components like water cylinders or storage tanks need to be removed, the new combi boiler installation can occur in about 1-2 days. 

Replacing a system boiler with a combi

Replacing a system with a combi

Changing from a system boiler to a combi boiler costs around £1,500 - £3,000. However, prices may be higher because the installation process is longer than that of swapping an old combi boiler with a new combi boiler. 

Fitting a combi boiler to replace a system boiler involves removing the hot water cylinder and potentially adjusting the pipework. This can take about 2 days or more to complete, so you can end up spending more on labour costs. 

Changing from a regular boiler to a combi

Replacing a regular with a combi

If you’re switching from a regular boiler or conventional boiler, you can expect to pay somewhere between £2,500 and £4,500. This kind of replacement is the most costly, as it requires the removal of a feed and expansion tank in the attic as well as a hot water storage cylinder. 

The combi boiler gets its water supply directly from the mains and so more pipework will be required. As a result, having a combi boiler fitted to replace a regular boiler can take 2.5 days or more, depending on the complexity of the installation. 

If you’re looking to change up your heating system and want to obtain the best prices, check out our service for free, non-binding quotes from engineers. Changing your heating requires a reliable installer and we can provide you with up to 3 quotes from different Gas Safe registered engineers who you can trust.

Click the button below and cut down on all the costs you are incurring with an older, inefficient boiler.

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Installing a new central heating system

The costliest option is (unsurprisingly) installing a completely new central heating system from scratch. This could cost between £2,000 - £5,000, depending on the size of your home and the complexity of the installation. The job could take 4+ days to complete, meaning that you would also be spending more on labour costs.

Why should you install a combi boiler?

Advantages of installing a combi boiler

Advantages of installing a combi boiler

Compared to their counterparts, combi boilers can be far more space-efficient, particularly in comparison to conventional gas boilers. This is due to their compact build and their lack of additional elements such as cisterns or large tanks.

Combi boilers are also more energy-efficient which can spare you some egregious energy bills. While gas boilers have an efficiency rating of around 93%, most electric combi boilers can boast one as high as 99%-100%. This can keep the strain on your energy bills at bay and allows you to reduce your carbon footprint if your electricity is coming from a renewable source

You can also save on your new combi boiler installation costs (depending on your setup). Combi boilers forgo the need for complex pipework, making them simpler and cheaper to install. A cheap boiler is usually the most cost-effective option to heat a home, so you can check which combi boiler you can get for less.

Combi boilers also heat water using an “on-demand” system, which allows them to do it instantly. Rather than storing it for future use, they heat it on the spot, ensuring adequate temperatures when needed. This can be especially useful in facilities with long queues for hot water.

It is worth noting, however, that the lack of water storage makes them unsuitable for houses with higher water demand. Simultaneously using multiple showers, for example, could diminish the levels of hot water a combi boiler can handle.

What to consider when installing a combi boiler

When installing a combi boiler, it is important to keep in mind how much water your household uses on a daily basis. If you require multiple showers running simultaneously, combi boilers may not be the best option for you. In these cases, a system boiler may be better, if you have the space for the additional elements that come with it.

Combi boilers, as already mentioned, are more compact and thus may be suitable for the type of home you have. If you would like to free up space or live in a smaller apartment, they can be the best option.

Similarly, you should consider the cost of upgrading your current heating system. While these can seem high, there are quite a few grants that might alleviate the boiler replacement and installation costs.

When to get a new combi

If you're without heating and hot water, then your reasons for getting new boiler quotes are quite straightforward! However, you shouldn't wait for your boiler to breakdown to opt for a new combi boiler installation. There are many signs that you need a new boiler. Some of the combi boiler installation requirements to consider include: 

When to get a new combi boiler installation

Your boiler is over 8 years old

The average boiler lifespan is somewhere around 10-15 years. So if your boiler is getting close to this age, now might be a good time to get quotes for a replacement. Replacing it before it packs in can save you a nasty surprise. At the very least, you’ll know what kind of costs you’re looking at when the time comes.

Your boiler needs repairing more and more

Boilers can become more unreliable as they age. Calling out an engineer time and time again to repair it will see the costs soon add up. While the upfront cost of a new combi boiler installation can be daunting, you may well save more in the long run by avoiding ongoing repairs. In addition, you may find that while your boiler hasn’t died completely, the cost to get it running again could be close to a brand new boiler.

Your heating bills are high

Modern condensing boilers are more efficient than non-condensing boilers. This can save you a significant amount of money on your heating bills. Depending on the boiler you’re replacing and the size of your home, you could see annual savings of as much as £580 with a new boiler (Energy Saving Trust, February 2024).

You might be selling your home in the future

According to recent research, adding a new energy-efficient boiler to your home can significantly increase its value, which can be beneficial for you if you're planning on selling your home in the future. Knowing that they’re buying a home with a new heating system is a real selling point for potential buyers.

If you’re looking to change up your heating system, Boiler Guide’s service is the best way to obtain quotes from trusted professionals for your new combi boiler. Finding installers on your own can be difficult. With so many options to choose from, you can spend hours comparing installers and service costs. To help you avoid wasting your time, we can provide you with quotes from local installers vetted by us. 

Make sure you cut down on your heating costs, increase your home’s value, and avoid expensive repairs by clicking the button below to receive up to 3 free, non-binding quotes from reputable heating engineers in your area.

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Find the right combi boiler

Combi boilers are the most commonly installed in the UK and there are plenty of models to choose from.

Your choice of manufacturer may come down to personal preference. For example, if you’ve always had the same brand and are happy with it. Or, you may want to ask a professional for their recommendation. Most people are also likely to be swayed by the price - which will vary from manufacturer to manufacturer.

Combi boilers come in a range of outputs (sizes) which are measured in kilowatts (kW). The right size boiler for your home will depend on the number of radiators and bathrooms you have. The bigger your home, the more powerful the boiler will need to be.

If you have more than one bathroom, a combi boiler may struggle to meet your household's needs. This is because it heats water on demand and sends it straight to the tap when you need it. If hot water is needed from two taps at the same time, then the pressure will drop.

This table gives you an idea of the kind of boiler outputs usually recommended by type and size of home:

Type of House Bedrooms Bathrooms Radiators Boiler size
Small terrace, flat or bungalow 1-2 1 Up to 10 18-27kW
Medium terrace, bungalow or semi-detached house 3-4 2-3 Up to 15 28-34kW
Large semi-detached or detached house 5+ 4+ Up to 20 35-43kW

Combi boiler installation near me

A gas boiler installation has to be carried out by a Gas Safe registered engineer to ensure it meets building and safety regulations. If you need an oil boiler installation, you should find an OFTEC-registered engineer.

Gas Safe registered engineers

Only engineers listed on the Gas Safe register are legally allowed to work with gas appliances. You can check if an engineer is on the Gas Safe register on the Gas Safe website and should always ask to see an engineer’s Gas Safe ID before they begin work in your home. The ID will not only confirm that they are competent but also which types of appliances they are able to work on.

We know that you should never attempt to install a boiler yourself. This is not only dangerous, but will also put your home at risk. Plus, even if you did get the boiler installed, it will still need to be checked and signed off by a professional - and most Gas Safe engineers will not sign off work they haven't done themselves. In addition, a boiler that hasn't been fitted by a Gas Safe engineer will no longer be covered by the manufacturer’s warranty.

Manufacturer accredited installers

Many manufacturers have their own installer accreditation schemes. If an engineer is affiliated with a particular manufacturer in this way, choosing them to install your boiler means you may be entitled to a longer warranty.

Get the best combi boiler installation quotes

Comparing quotes from multiple engineers is the best way to keep the costs of your new combi boiler installation down and ensure that you're getting top advice. Instead of spending hours looking up the costs of different installers, let us help you get started in just 30 seconds. 

Simply fill in our short form and wait for up to 3 engineers in your area to reach out to you with quotes for their services. Once you’ve received your quotes, compare them to find the right person for the job and secure the best deal for your new combi boiler installation. Thanks to our service, you will get to work with only the best professionals and save hundreds on your heating bills. 

Click the button below to find a trustworthy engineer for your combi boiler installation.

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FAQ

Are combi boilers easy to install?

Yes, combi boilers are fairly easy to install and the process can be finalised in about 1-2 days. However, in some cases the installation process will be more complex depending on the kind of combi boiler you choose and what type of boiler swap you require.

Can I install a combi boiler myself?
It is extremely ill-advised to install your own combi boiler because it can be dangerous for you and your home. It's best to find a Gas Safe registered engineer to help you.

How long does a combi boiler installation take?
Combi boiler installation can be as quick as 1 or 2 days, while more extensive heating system replacement can take upwards of 4 days. This timescale can depend on a few factors that may take longer, but generally, they are quick to install.

What happens during a combi boiler installation?
An engineer will come over and look at your home setup, assess the work that needs to be done, and provide you with a quote. Once you agree to a price, they will prepare your home, install it, and show you how to operate it. The process for replacing a system can be different but involves many of the same steps.

Can I replace my old boiler for a combi boiler?
Yes, you can! It's not out of the ordinary to swap one type of boiler for another but the price of the installation can vary on the type of boiler that needs to be replaced.

Nick Geary

About the author

Nick Geary

Nick has a wide range of experience writing about conventional and renewable heating solutions, and is always increasing his knowledge by researching any new heating technologies on the horizon.

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