UK 2026 cost guide / Updated November 2026
Boiler replacement cost UK 2026: £3,500 on average, fixed prices from £1,890.
The Energy Saving Trust puts the average cost of replacing a G-rated gas boiler with an A-rated one, with thermostatic radiator valves, at £3,500 in Great Britain. The lowest published fixed price we found is BOXT's £1,890 for a Navien NCB 300 30kW combi, supplied and fitted (checked 14 November 2026). That is a floor for a straightforward combi swap; a bigger output, a type change or a boiler move costs more.
Independent. Not affiliated with any boiler manufacturer, installer, or finance provider. Other cited sources: manufacturers' warranty terms, DESNZ Boiler Upgrade Scheme statistics, gov.uk and Ofgem grant pages, Gas Safe Register requirements, and Boiler Plus 2018.
Your four options, side-by-side
Every working boiler eventually arrives at this fork. Each branch shows the published figure where one exists, and says "quote" where nobody publishes a price. Click a branch to see the depth page.
Repair
Quote per fault
Single-fault fix on the existing boiler: PCB, pump, diverter valve or heat exchanger. Price depends on the part and your engineer.
Best when
Boiler under 10 years old, first major fault, repair cost under 50% of a swap.
More on this option →Like-for-like swap
From £1,890
Same fuel, same boiler type. BOXT fixed price from £1,890; the Energy Saving Trust average is £3,500.
Best when
Boiler over 12 years old, breakdowns getting frequent, no need to change fuel or layout.
More on this option →Convert (e.g. back boiler to combi)
Quote only
New pipework + flue + decommission existing setup. Back boiler conversion, regular-to-combi, system-to-combi.
Best when
Awkward layout in current system, wanting to free up loft tank space, modernising heating.
More on this option →Heat pump alternative
£12,826 median
Air source heat pump, Boiler Upgrade Scheme installs, Jul-Sep 2026 (DESNZ). About £5,326 after the £7,500 grant. No gas at all.
Best when
Well-insulated home, EPC C+ ideally, room for an outdoor unit, and an MCS certified installer.
More on this option →A common rule of thumb: repair while the quote is under about half the cost of a like-for-like swap. The convert branch pays for extra pipework and a new flue in exchange for a cleaner layout. Heat-pump figures are the median reported cost of air source installs under the Boiler Upgrade Scheme, DESNZ statistics for July to September 2026. That branch trades a higher upfront cost for the £7,500 BUS grant and matches the direction of the Future Homes Standard, which requires low-carbon heating in new homes in England from March 2027.
Quick answer: three published reference points
Average replacement (EST)
£3,500
Energy Saving Trust average for replacing a G-rated gas boiler with an A-rated one, with radiator valves, Great Britain. energysavingtrust.org.uk
Lowest fixed price (BOXT)
From £1,890
Navien NCB 300 30kW combi, supplied and fitted, checked 14 November 2026. The floor for a simple combi swap. boxt.co.uk
Air source heat pump (DESNZ)
£12,826 median
Boiler Upgrade Scheme installs, July to September 2026, before the grant. About £5,326 after it. gov.uk BUS statistics
Cost by boiler type
Only combi boilers have a published fixed installed price that we could find. System, regular and back-boiler jobs depend on the cylinder, tanks, pipework and flue, so installers price them by survey. Treat the Energy Saving Trust's £3,500 average as the reference point and compare written quotes.
| Type | Published price | Install time | Best for | Deep dive |
|---|---|---|---|---|
| Combi | From £1,890 (BOXT) | 1 day | 1-3 bed homes, one bathroom | Combi cost |
| System | Quote after survey | 1-2 days | 3+ bed, 2+ bathrooms, hot water cylinder | System cost |
| Regular (heat-only) | Quote after survey | 1-2 days | Older homes with loft tank, large like-for-like | Regular cost |
| Back boiler conversion | Quote after survey | 2-3 days | 1960s-1980s houses with back boiler behind gas fire | Back boiler cost |
What is included in a typical UK replacement quote
A reputable Gas Safe registered installer should itemise every line. If the quote is a single all-in figure with no breakdown, ask for one. Six line items should appear on every replacement quote:
Boiler unit
Named modelAsk for the make, model and output by name, and the warranty term the installer will register. Manufacturers do not publish consumer prices; compare like-for-like quotes instead.
Installation labour
Days on siteAbout a day for a like-for-like combi swap, longer for a type change or a boiler move. Ask how many engineer-days the price assumes.
Flue + fittings
Flue routeStandard horizontal flue is cheapest. Vertical flue through the roof or longer runs (over 2m) cost more. Flue must meet Part J distance rules from windows and doors.
Magnetic system filter
Make and modelTraps debris before it damages the heat exchanger. Now required by most manufacturers to validate extended warranties.
Powerflush or chemical flush
Included or extraStrongly recommended on systems over 10 years old. Some installers include it, others charge separately; check before signing.
Building Control notification
Should be includedGas Safe installers self-certify under the Competent Persons Scheme. The certificate should be in the quote.
Cost by house size
Larger homes need higher-output boilers, more radiators, and longer install times. The output and type below are common starting points for a quote, not a heat-loss calculation; your installer should size the boiler to your home. For model-by-model installed prices at each output, see cost by brand.
| Property | Recommended kW | Best type |
|---|---|---|
| 1-bed flat | 24 kW | Combi |
| 2-bed terrace | 24-28 kW | Combi |
| 3-bed semi | 28-30 kW | Combi |
| 4-bed detached | 30-35 kW | Combi or system |
| 5+ bed large home | 35+ kW | System + cylinder |
Brand quick compare
Installed prices are BOXT's published fixed "from" prices, checked 14 November 2026. Warranty terms are from each manufacturer's own UK warranty pages. Baxi and Viessmann have no published installed price.
Worcester Bosch
Installed from £2,249
Warranty: Up to 12 years on the Greenstar 8000 Life when fitted by a Worcester Bosch Accredited Installer
UK (Worcester), part of the Bosch group
Vaillant
Installed from £2,569
Warranty: Up to 10 years on ecoTEC plus, ecoTEC exclusive and ecoFIT pure (up to 45 kW) with the Advance Boiler Protection Kit, registered through Advance
Germany (Remscheid), Vaillant Group
Ideal
Installed from £2,110
Warranty: Up to 12 years on Vogue Max combi and system; 10 years on Logic Max combi, system and heat
UK (Hull)
Baxi
No published installed price
Warranty: 10 years on the 800 Combi 2 and 800 System 2; 7 years on the 600 Combi 2 and 600 System 2
UK, part of BDR Thermea Group
Viessmann
No published installed price
Warranty: 2 years standard, 7 years free on registration; Vitodens 100-W and 200-W can be extended to 10 or 12 years for a fee
Germany (Allendorf)
Grants and finance: who pays less
Two government schemes can reduce or eliminate the upfront cost. Plus 0% finance via approved installers is the standard spread-cost route.
ECO4 scheme
Free boiler possibleFunded by energy suppliers under an Ofgem-administered obligation that runs until 31 December 2026. For households on qualifying benefits whose home is EPC D to G (E to G if privately rented). A broken efficient boiler is replaced only if it cannot be economically repaired, and suppliers may ask for a contribution.
Read full ECO4 eligibility guide →Boiler Upgrade Scheme
£7,500 grantHeat pumps only, not gas boilers. £7,500 for air source or ground source heat pumps, £2,500 for air-to-air, £5,000 for biomass boilers in rural off-gas properties. Applied for by the MCS certified installer, not the homeowner. England and Wales only.
Read full BUS guide →Not eligible for grants? See 0% finance options for spreading the cost.
How to use this site
If you're not sure your boiler needs replacing at all, start with 8 signs you need a new boiler then read repair or replace. If you know you're replacing, jump straight to cost by type or cost by brand. If you're considering a heat pump, start with gas boiler vs heat pump cost.
Prices on this page come from BOXT's published fixed installed prices, the Energy Saving Trust and DESNZ Boiler Upgrade Scheme statistics; grant terms from gov.uk and Ofgem. Where no one publishes a price, we say so rather than estimate one. See methodology for the full source ledger.
Frequently asked questions
How much does it cost to replace a boiler in the UK in 2026?
The Energy Saving Trust puts the average cost of replacing a G-rated gas boiler with an A-rated one, with radiator valves, at £3,500 in Great Britain. BOXT's lowest published fixed price is £1,890 for a Navien NCB 300 30kW combi, supplied and fitted (checked 14 November 2026). A type change, back-boiler conversion or boiler move adds pipework and flue work that is priced by survey.
Is it cheaper to repair or replace an old boiler?
A useful rule of thumb is to repair while the quote is under about half the cost of a replacement; get it quoted in writing, part by part. If your boiler is under 10 years old and this is its first major fault, repair is almost always the right call. Over 12 years old with two or more callouts in the last year, replacement starts winning on whole-cost terms.
What grants are available for boiler replacement in 2026?
ECO4 (an obligation on energy suppliers, administered by Ofgem, running until 31 December 2026) for households on qualifying benefits in an EPC D-G home (E-G if privately rented); a working-but-broken efficient boiler is only replaced if it cannot be economically repaired. The Boiler Upgrade Scheme gives £7,500 towards a heat pump, not a gas boiler. Local councils may also offer means-tested grants.
Should I switch to a heat pump instead of replacing my gas boiler?
Worth modelling, but rarely the right answer unless the property is already insulated to EPC C or better. Air source heat pumps installed under the Boiler Upgrade Scheme in July to September 2026 had a median reported cost of £12,826, about £5,326 after the £7,500 grant (DESNZ). Running costs are comparable to a high-efficiency gas combi in a well-insulated home, higher in a poorly insulated one.
How long does a boiler replacement take?
Like-for-like combi swap: 6-8 hours, done in a day. Boiler type change: 1.5-2 days. Back-boiler conversion: 2-3 days.
Do I need a Gas Safe registered engineer?
Yes. By law all gas boiler installations in the UK must be carried out by a Gas Safe registered engineer under the Gas Safety (Installation and Use) Regulations 1998. Verify the engineer's ID at gassaferegister.co.uk.
Related independent guides
Prices on this page last verified 14 November 2026. See methodology for the full source ledger and refresh cadence.