How much does a combi boiler cost in 2026?
A working price index for UK homeowners replacing or installing a combination boiler. Indicative supply-and-fit ranges, kW sizing, brand-by-brand fairness, and the running cost to budget for once it is on the wall.
Indicative supply & fit
£1,800 to £3,500
Range / not a quote
Boiler unit
£500 to £1,500
Budget to premium brand
Fitter labour
£800 to £2,000
Like-for-like to full convert
Drawn from Boxt, Heatable, and British Gas typical quotes plus Gas Safe installer surveys. Add 10 to 25 percent in London and the South East.
Fig.01 / Cutaway
Wall-hung combi
- A Heat exchanger
- B DHW plate
- C Gas valve
- D Balanced flue
No.01
No postcode required
Walk in with a fair-price benchmark. We never gate the answer behind a quote form.
No.02
Combi-only depth
Sized, priced, and explained for combination boilers, not generic boiler content.
No.03
Independent price index
We are not a fitter, retailer, or lead broker. We point you at three Gas Safe quotes.
Tool / 01
Combi boiler cost estimator
Pick a brand, output, and install type. The tool returns an indicative price band with a breakdown for the unit, fitter labour, and any extras.
Spec your job
Extras (tick what applies)
Indicative quote
Range / not a quote
Total supply & fit
£1850 to £3050
Sizing / Cost
Cost by kW output
Output is set by hot-water demand, not floor area. Match bathroom count and simultaneous outlets first, then check the radiator count.
| Output | Suited property | Bathrooms | Flow rate (35C rise) | Indicative supply & fit |
|---|---|---|---|---|
| 24 kW | 1 to 2 bed flat | 1 | around 10 LPM | £1,800 to £2,500 |
| 28 kW | 2 to 3 bed house | 1 | around 12 LPM | £2,000 to £3,000 |
| 30 kW | 3 bed semi | 1 to 2 | around 13 LPM | £2,200 to £3,200 |
| 35 kW | 4 bed detached | 2 | around 15 LPM | £2,500 to £3,500 |
| 40 kW+ | Large home, 3+ baths | 2 to 3 | 17 LPM and up | £3,000 to £4,000 |
LPM = litres per minute, the volume of hot water the boiler can deliver. A comfortable shower wants 9 to 12 LPM. Two simultaneous showers need 35 kW or above.
Hot water capacity
Flow rate is the trap most buyers miss
A combi heats hot water on demand. There is no cylinder reserve. The kW number you choose decides whether the second tap stays hot when someone is in the shower.
Use the ladder to read off realistic flow rates per output size at a typical 35C temperature rise. Winter mains are colder, so add roughly 15 percent to your selected output to keep flow strong in January.
Fig.02 / DHW flow rate
Litres / min @ 35C rise
24 kW
28 kW
30 kW
35 kW
40 kW
A comfortable shower wants 9 to 12 LPM. Two simultaneous showers need 15 LPM and up. Winter mains are colder, so add roughly 15 percent to your output target to keep flow strong from December to February.
Brand index
Indicative price by brand
Five brands cover most UK installations. Spec-level differences are real, but installer quality typically matters more than the badge.
Brand
Worcester Bosch
Typical model
Greenstar 8000 Life
- Unit
- £800 to £1,500
- Supply & fit
- £2,400 to £3,800
- Warranty
- Up to 12 years
Aluminium heat exchanger. Strongest engineer support of any UK brand.
Brand
Vaillant
Typical model
ecoTEC Plus 832
- Unit
- £700 to £1,400
- Supply & fit
- £2,200 to £3,500
- Warranty
- Up to 10 years
Stainless steel heat exchanger. 1:10 modulation, very quiet at low load.
Brand
Viessmann
Typical model
Vitodens 050-W
- Unit
- £900 to £1,600
- Supply & fit
- £2,500 to £4,000
- Warranty
- 10 to 12 years
MatriX cylinder burner. The pick if low noise matters most.
Brand
Ideal
Typical model
Vogue Max
- Unit
- £600 to £1,000
- Supply & fit
- £1,900 to £3,000
- Warranty
- Up to 12 years
British-built. The longest warranty for the money in 2026.
Brand
Baxi
Typical model
Baxi 800
- Unit
- £550 to £950
- Supply & fit
- £1,800 to £2,800
- Warranty
- 7 to 10 years
Strong parts availability. Common spec for letting-agent properties.
Line items
What can push the price up
These line items appear on a fitter's quote. Tick the ones that apply to your property, the rest are optional or only relevant on certain conversions.
MagnaClean magnetic filter
£100 to £150
Captures iron sludge. Cheap insurance for the heat exchanger and now demanded by most warranties.
Powerflush
£300 to £500
Older systems with sludge in the radiators. Skipping it on a knackered system can void the warranty.
Moving the boiler
£300 to £500
New flue, gas, and water runs. Often paired with a kitchen refit.
New flue (different position)
£100 to £300
Required when the boiler relocates or the existing flue is the wrong type.
Gas pipe upgrade to 22 mm
£100 to £200
Older homes have 15 mm supply. A 30 kW+ combi will not run safely without the upgrade.
Removing cylinder & loft tanks
£200 to £400
Only on a regular-to-combi conversion. Includes capping pipework and making good.
Smart thermostat (Nest, Hive, Tado)
£150 to £300
Optional. Pays back in around 1 to 3 years from gas savings if you set it up properly.
Asbestos flue removal
£200 to £500
Pre-1980s properties only. Specialist removal, must be done by a licensed contractor.
Six dials
Six things that move the price
01
Brand pick
Premium German over British budget can swing the unit cost by £600 or more before fit.
02
kW output
Going from a 24 kW to a 35 kW unit on the same brand adds roughly £200 to £400 to the supply cost.
03
Install type
Like-for-like is cheapest. Back-boiler conversion is the most expensive due to building work.
04
Boiler location
Moving the boiler to a different room or wall adds £300 to £500 plus a new flue.
05
Region
London and the South East run roughly 15 to 25 percent above the national average for labour.
06
System condition
An old system needs a powerflush and often a magnetic filter. Newer systems do not.
Buying step
Three quotes, Gas Safe verified
The right benchmark is three written quotes from Gas Safe registered engineers (gasaferegister.co.uk). Cheapest is not always best, but a quote that is way under the others usually means a corner is being cut.
Online retailers (Boxt, Heatable, British Gas typical quotes) also publish fixed prices on their websites. They are useful for benchmarking your local fitter.
- 01
Verify the badge
Check the engineer's Gas Safe ID card on the official register before any work starts. The card has a unique number and a photo.
- 02
Itemise the quote
Boiler model, kW, labour, flue, disposal of the old unit, commissioning, extras (filter, flush, thermostat), warranty length, and VAT, all on one page.
- 03
Brand-accredited fitter
For the longest warranties (10 to 12 years), the installer must be on the manufacturer's accredited installer list.
- 04
Watch for the red flags
Cash only with no invoice. No written quote. Pressure to decide on the spot. Reluctance to show ID. Skipping the powerflush on a clearly old system.
Twelve guides, no quote forms
Best Brands
Worcester, Vaillant, Viessmann, Ideal, Baxi compared.
What Size?
Sizing tool plus a flow-rate ladder by kW.
Installation Guide
Labour cost, day-by-day timeline, extra charges.
Converting to Combi
Regular, system, and back-boiler conversions priced.
Running Costs
Annual gas bills by property and old vs new savings.
Combi vs System
When a combi is the right shout, and when it is not.
ECO4 Grants
ECO4 extension to December 2026 and 0 percent finance.
Servicing
Annual service, boiler cover plans, repair-or-replace thresholds.
Warranty
Standard, extended, and what voids each brand.
Regional Costs
London premium and the cheapest UK regions.
Lifespan
How long they last and signs they need replacing.
FAQs
Common questions
How much does a combi boiler cost to supply and fit in 2026?v
Indicative quotes for a new combi boiler supplied and fitted run from around £1,800 to £3,500 for most UK homes in 2026. The unit itself sits in the £500 to £1,500 band depending on brand and kW. Installation labour adds roughly £800 to £2,000 depending on the type of swap and any extras such as a powerflush or new flue.
Does the price include removing the old boiler?v
Yes, in most cases. Reputable Gas Safe installers include removal and disposal of the old boiler in the headline quote. Removing a back boiler from behind a fireplace is the exception, that often adds an extra £200 to £400 in builder's work plus making the hearth good.
How long does combi boiler installation take?v
A like-for-like swap takes about one day. Relocating the boiler or converting from a back boiler typically runs to two days. A full conversion from a regular (heat-only) boiler to a combi can stretch to two or three days because tanks and the cylinder must come out and the gas pipe is often upgraded.
Is there government help with the cost?v
Possibly. The ECO4 scheme was extended to December 2026 and can fund a free boiler replacement for households on qualifying benefits with a low EPC rating. The Boiler Upgrade Scheme covers heat pumps rather than gas combis. Most installers also offer 0 percent finance, and personal loans are an option for spreading the cost.
Which combi boiler brand is most reliable?v
Worcester Bosch and Vaillant lead UK Gas Safe engineer surveys for reliability and ease of repair. Viessmann is the premium pick for quietness and long-term efficiency. Ideal Vogue Max offers up to a 12 year warranty at a mid-range price. Baxi is the value pick, popular with letting-agent specifications.
What is the cheapest combi boiler installed?v
Budget brands such as Baxi 600 or Ideal Logic Max can come in at the lower end of indicative quotes from fixed-price online retailers (Boxt, Heatable, British Gas typical quotes). Expect around £1,800 supplied and fitted for a straightforward swap on a 24-28 kW unit.