How Much Does a New Boiler Cost?
Written by James Walker · Last reviewed 15 August 2026
James Walker has 2 degrees in construction (BSc (Hons) Building Surveying · MSc Environmental Design of Buildings) and an extensive background in issue resolution, resolving over £4 billion of consumer issues.
The short answer
- A like-for-like combi replacement typically costs £1,800–£3,000 installed.
- Changing system type, conventional to combi, costs considerably more.
- The Benchmark certificate and warranty registration are part of what you are buying.
- Oversizing is common and costs you money for the life of the boiler.
- Prices last updated August 2026.
On this page
Cost by job type
| Scope | Typical range | Mid-point |
|---|---|---|
| Like-for-like combi swap | £1,800–£3,000 | £2,300 |
| New combi, standard install | £2,400–£3,800 | — |
| System boiler with cylinder | £3,800–£5,500 | — |
| Conventional to combi | £3,000–£4,500 | — |
What pushes the price up
Changing system type. Converting a conventional system to a combi means removing tanks, altering pipework and often re-running the gas supply. It is a different job from a swap.
Moving the boiler. Relocating means new flue, new gas run, new condensate route, and making good.
Flue route. Awkward flue positions, or those requiring extended runs or roof terminations, add cost.
Gas supply pipe. Older properties often have a supply pipe too small for a modern boiler. Upgrading it can mean a long run through the house.
System condition. A flush is standard; a badly contaminated system may need more, and skipping it can void the warranty.
Controls. Modern efficiency requirements mean controls and zoning that older systems did not have.
How long it takes
1–3 days.
How to stage the payments
Completion payment set aside, kick-off of 15-20% against the boiler, then final on commissioning. Hold the final 10% until you physically have the Benchmark certificate completed, confirmation the warranty is registered, and the building control notification.
Keeping the cost down
- Like-for-like replacement in the same position is much cheaper than relocating
- Do not buy more output than the heat loss calculation supports
- Get the flush, a declined warranty claim costs more than the flush
How it works
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