Do you have an old system and want to know what's involved when installing a new boiler? We have you covered in this guide.
Want to replace your old boiler?
Whether you’re curious about what the process involves, how much it costs, or how long the work takes - you’re in the right place.
In this guide, we’ll cover everything you need to know about replacing an older boiler, including typical prices, installation steps, and how to get the best deal.
PS we fit new boilers with gas installation nationwide. Simply answer these questions, get your fixed price and you could get it installed as quick as tomorrow.
Cost of Fitting a New Boiler to an Old System
With supply and labour costs taken into account, the cost of replacing an older boiler with a new one will almost always cost several thousand pounds.
Please be aware that all cost ranges featured in this section are estimates and some jobs could have price tags outside the ranges given below.
There are two broad categories of boiler replacements: like-for-like and conversion.
The former means that you are having your boiler replaced with the same type (e.g., a combi boiler replacing an existing combi boiler) whereas a boiler conversion involves switching type (e.g., replacing a regular boiler with a system boiler).
With supply and labour included, a new boiler replacement typically costs between £1,500 and £4,500 - though this can vary based on the type of boiler and complexity of the job.
Below are realistic price ranges for 2025, verified using data from Heatable…
Replace a Regular Boiler with:
Combi Boiler - £2,500 to £4,000.
System Boiler - £2,500 to £4,500.
Regular Boiler - £2,500 to £4,500.
Replace a Combi Boiler with:
Combi Boiler - £1,250 to £3,650.
System Boiler - £1,250 to £4,150.
Regular Boiler - £1,250 to £4,150.
Replace a System Boiler with:
Combi Boiler - £1,250 to £3,650.
System Boiler - £1,250 to £4,150.
Regular Boiler - £1,250 to £4,150.
If you want to have a biomass boiler installed, you’re probably looking at paying over £10,000 and perhaps even close to £18,000 for the most expensive options.
Curious to know what the best boiler brands are on the market? Check out our popular guide of the ten best boiler brands to buy.
Cost-affecting Factors of a Boiler Replacement
The figures given in the previous section are, as mentioned, just estimated price ranges. Let’s look at the factors that shape these price estimates.
Cost Factors of Replacing a Boiler include:
Size and type of existing boiler being removed.
Size and type of new boiler being installed.
Whether you are changing the system.
Whether you intend to have your boiler relocated.
Ease of access.
State of the work area.
The region of the UK you live in*
If scaffolding is needed^
*As for where you are based, this is relevant because labour costs differ throughout the UK. Prices tend to be lower in northern England, Scotland, and Northern Ireland. On the other hand, they are usually above average in southeast England. London is notorious for its high prices.
^It is rare that scaffolding would be required. However, if the flue is difficult or/and unsafe for a heating engineer to reach even with a ladder, they’ll need to use scaffolding.
What Does Replacing an Old System with a New Boiler Involve?
We’ll now break down the various steps that are generally involved in replacing an old system with a new boiler.
Please be aware that these steps must be completed by a Gas Safe registered engineer and are not suited for a DIY enthusiast.
Broadly speaking, here is how an old system is replaced with a new boiler:
The existing central heating system (CHS) is powered off and the power isolated at the mains
The old boiler and fittings are removed
The new boiler is installed including the pipework
If applicable, a new water storage tank will be added (e.g., a combi boiler being replaced with a system boiler would require a new separate water storage tank, mostly likely in the loft)
All relevant connections and remaining work are complete and checked to ensure everything is good
The power is turned back on before the new CHS is powered up
The new CHS is tested
If everything is good, it is now safe to use
Any necessary clean up can now be undertaken (some of the clean-up will take place during the previous steps) and the old CHS can be disposed of
Where do you get rid of an old boiler/CHS?...
In most cases, the engineer themselves will be able to get rid of the old boiler.
Otherwise, contact your local council prior to having it removed by a professional for guidance. A boiler and central heating components must be disposed of properly.
Note: You may also wish to have your central heating system flushed as part of the replacement work.
We’ll now look a little more at the different potential aspects of a boiler replacement…
Do You Need to Change System?
A like-for-like boiler swap is generally quicker and cheaper, but in some cases it makes sense to convert.
For example:
Regular → Combi: frees up loft space and removes tanks.
System → Combi: ideal for smaller households needing instant hot water.
Combi → System: better for larger families with multiple bathrooms.
System changes involve extra work such as:
Removing or adding hot-water cylinders
Adjusting pipework and valves
Upgrading boiler controls
Regular (heat-only) boilers are best replaced like-for-like, as converting them involves extensive pipework changes.
Relocating Your Boiler
Want your new boiler in a different room?
That’s possible - but expect additional costs (typically £300–£800 extra) and longer installation time.
You may, for instance, wish to have the new boiler fitted in a different room for practical or even visual purposes.
Relocating the placement of your home’s boiler would involve the pipework being redirected.
Boiler Replacement Work Duration
The time it takes for a boiler to be replaced will, just like the price tag, depend on a variety of factors.
Across the board, it takes around one to three days to replace an old boiler with a new one. It should take no more than five days.
Time Factors of Replacing a Boiler:
Size and type of existing boiler being removed.
Size and type of new boiler being installed.
Whether you are changing system.
Whether you intend to have your boiler relocated.
Ease of access.
State of the work area.
If scaffolding is needed.
Get A New Boiler Quote Today
If you’re aiming to get the best deal on a new boiler, consider getting your boiler installation with us. Here’s why:
Gas Safe installation within 24 hours.
Thousands of satisfied customers with an average score of 4.9 on Trustpilot, surpassing the market leader.
Which? Trusted Trader: Heatable is proudly recognised as a Which? Trusted Trader.
Price match guarantee: We will match any like-for-like cheaper quote.
Flexible payment options, including interest-free finance*.
Up to a 12-year guarantee on selected boilers.
Fixed price guarantee: No hidden costs.
Save your quote and decide later.
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