How much does a boiler replacement cost in the UK?
As an indicative planning range, a straight combi-for-combi swap commonly falls somewhere around £1,800–£3,200 fitted, while a system change, a relocation or a larger output boiler more often lands in the £3,000–£5,500 region. The boiler itself is usually the smaller half of the figure: labour, flue work, controls, flushing and making good carry much of the cost.
Boiler quotes are hard to compare because two installers can price genuinely different jobs under the same heading. One may be swapping like for like on the existing pipework in a day; another may be moving the boiler, running a new gas supply, upgrading the flue and fitting a filter and smart control.
Gas work must be carried out by a Gas Safe registered engineer, and the installation must be notified to Building Control — usually done by the installer through the Gas Safe scheme. That notification, the commissioning and the manufacturer warranty registration should all be part of the price.
All figures on this page are indicative estimates for planning only. QuoteCheck does not hold a live UK pricing feed, and real prices vary with location, boiler brand, output, existing pipework, access and how each firm prices its labour.
Indicative UK cost ranges
QuoteCheck does not hold a live UK pricing feed. The figures below are indicative planning ranges, assembled from commonly published UK ranges and typical job structures, and they are deliberately wide. Treat them as a starting point for questions, not as a valuation. Real prices depend on specification, access, ground conditions, region, season and how each firm prices its own labour and overheads.
| Item | Unit | Indicative range |
|---|---|---|
| Combi boiler swap, same positionStraight replacement on existing pipework and flue route. | supplied and fitted | £1,800 – £3,200 |
| Combi boiler, relocatedNew gas run, condensate route, flue and making good. | supplied and fitted | £2,600 – £4,500 |
| Conventional to combi conversionTank and cylinder removal, pipework changes, decommissioning. | supplied and fitted | £3,000 – £5,500 |
| System boiler with cylinderHigher where an unvented cylinder and new controls are included. | supplied and fitted | £3,200 – £6,000 |
| Boiler unit onlyVaries by brand, output and warranty length. | per unit | £700 – £2,200 |
| LabourMost swaps are one to two days; conversions can be three to five. | per day | £300 – £600 |
| Vertical or extended flue kitRoof terminations cost more than a standard horizontal flue. | per job | £120 – £450 |
| Powerflush or chemical flushOften required to keep the warranty valid. | per job | £300 – £700 |
| Magnetic filterCommonly a warranty condition; should be itemised. | per item | £100 – £220 |
| Smart or programmable controlDepends on the control and whether zoning is added. | per item | £120 – £350 |
| Removal and disposal of old boiler / tanksHigher where a loft tank and cylinder come out. | per job | £80 – £300 |
What moves the price
- Boiler type
- Combi, system or conventional. Changing type is a different job from replacing like with like.
- Output (kW)
- Output should follow a heat loss calculation and hot water demand, not simply match the old boiler.
- Brand and warranty
- Longer manufacturer warranties usually come with a higher unit price and specific installation conditions.
- Flue requirements
- Vertical flues, long runs and awkward terminations add parts and time.
- System changes
- Removing tanks, converting pipework, adding zone valves or an unvented cylinder.
- Gas supply
- An undersized existing gas run may need upgrading, which can add a day and a floor lift.
- Access and making good
- Loft or airing cupboard positions, lifting floors and replastering after pipe runs.
- Region
- Labour rates are typically higher in London and the South East.
Worked example — combi swap with relocation (illustrative only)
- Boiler unit, 28kW, 10-year warranty
- £1,250
- Labour, 2 days, Gas Safe engineer plus mate
- £900
- Flue kit and extension
- £220
- New gas run and condensate
- £280
- Magnetic filter and chemical flush
- £420
- Smart control
- £190
- Removal and disposal
- £120
- Indicative subtotal
- £3,380
- VAT at 20%
- £676
- Indicative total
- £4,056
Fictional arithmetic to show how a boiler total is built up. Your own quote may differ for entirely legitimate reasons.
What your quote should show
- Boiler make, model and output in kW
- Whether the output follows a heat loss calculation
- Gas Safe registration number of the installing engineer
- Flue type, route and any extension
- Whether a flush, filter and inhibitor are included
- Controls being fitted and whether zoning changes
- Removal and disposal of the old boiler, tanks or cylinder
- Making good after pipe runs, and whether decoration is excluded
- Building Control notification and warranty registration
- Labour days and VAT treatment
Before you agree to the quote
- What is normally included
- The boiler, fittings, flue, commissioning, Gas Safe notification, warranty registration and removal of the old unit. Most reputable quotes also include a flush and filter.
- What is usually excluded
- Decoration and plastering after pipe runs, asbestos handling, upgrading radiators, new pipework beyond the boiler area, and anything found once floors are lifted.
- VAT
- A VAT-registered installer adds 20% to a standard domestic replacement. Certain energy-saving installations can attract a reduced rate — ask the installer to state the rate applied on your job rather than assuming it.
- Staged payments
- A deposit toward the boiler is normal; a large cash payment before anything is ordered is not. Ask for stages tied to delivery and completion.
- How long a quote should stand
- Boiler prices move, so ask how long the figure holds. Two to four weeks is common.
- How long it takes
- A like-for-like combi swap is usually one day. A relocation is typically two, and a conventional-to-combi conversion often three to five.
- Questions to ask
- What output did you calculate and why? What warranty applies and what conditions keep it valid? Who notifies Building Control? What happens if the gas supply needs upgrading?
Frequently asked questions
How much does it cost to replace a boiler in the UK?
As an indicative estimate, roughly £1,800–£3,200 for a like-for-like combi replacement and £3,000–£5,500 where the boiler is moved or the system type changes. These are planning ranges, not quotations, and real prices vary with brand, output, pipework, access and region.
Why do boiler quotes vary so much for the same house?
Because they are often not the same job. Differences in boiler brand and output, flue work, flushing, filters, controls and how much making good is included can easily account for a four-figure gap between two honest quotes.
Do I need a powerflush when I replace a boiler?
Not always, but many manufacturers require the system to be cleaned and an inhibitor and filter fitted for the warranty to stand. Ask which method is being used — a full powerflush and a chemical flush are not the same thing or the same price.
Is VAT charged on a boiler replacement?
A VAT-registered installer normally charges 20% on a standard domestic boiler replacement. Some energy-saving measures attract a reduced rate in certain circumstances, so ask the installer to state the VAT rate and amount on the quote.
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