Combi Boiler Replacement Cost 2026 (UK)
Replacing a combi boiler costs £1,800–£3,200 supplied and fitted in 2026 for a straight like-for-like swap in the same position. A larger or premium model, a change of location, or upgrading from an old back boiler or conventional system pushes the price higher. A combi is the UK's most popular boiler because it gives instant hot water with no cylinder or tank. Here is what a replacement costs in 2026, when to swap like-for-like versus upgrade, and how to cut the bill.
Planning the work? Check what it usually costs, or work out your own estimate. The free quote form is at the top of this page.
2026 combi boiler replacement costs
| Job | Typical price (2026) | Time |
|---|---|---|
| Like-for-like combi swap (budget model) | £1,800–£2,300 | 1 day |
| Like-for-like combi swap (mid/premium) | £2,300–£3,200 | 1 day |
| Combi swap with relocation | £2,600–£4,000 | 1–2 days |
| Convert system/regular to combi | £3,000–£4,500 | 1–2 days |
| Add filter & power flush | +£400–£700 | +0.5 day |
Like-for-like or upgrade?
If your current combi is well-sized and well-placed, a like-for-like swap is quickest and cheapest — the engineer reuses the existing pipework, flue and fixings. Upgrading to a higher flow-rate model makes sense if your showers feel weak, while converting from a system or regular boiler to a combi removes the cylinder and tanks but costs more because of the pipework changes and system flush.
How to cut the cost
- Get three quotes: boiler prices and labour vary widely — comparing is the single biggest saving.
- Keep the location: staying in the same spot avoids flue and pipework charges.
- Right-size, don't over-size: a correctly sized combi is cheaper to buy and run.
- Ask about fixed-price packages: many installers bundle boiler, flush and filter with a long warranty.
When is it worth replacing?
If your combi is over 10 years old, repeatedly breaking down, or losing efficiency, replacement usually pays back through lower bills and a fresh 7–12 year warranty. A newer boiler with a one-off fault is almost always cheaper to repair than replace.
Combi replacement costs at a glance — 2026
Source: BestBuilders 2026 regional cost model · 519 UK towns
Full 2026 rate card
| Job | Typical cost (2026) | Notes |
|---|---|---|
| Like-for-like swap, budget brand | £1,800–£2,200 | Baxi, Glow-worm; 5–7yr warranty |
| Like-for-like swap, mid-range | £2,200–£2,700 | Ideal, Vaillant ecoFIT; 7–10yr |
| Like-for-like swap, premium | £2,700–£3,200 | Worcester 8000, ecoTEC, Viessmann; 10–12yr |
| Bigger output (extra bathroom) | +£150–£400 | 30–35kW over 24–27kW |
| Relocation within the house | +£400–£1,000 | See moving a boiler costs |
| System/regular to combi conversion | £2,500–£4,500 | Tanks and cylinder removed |
| Powerflush on a sludged system | +£300–£700 | Chemical flush often included free |
| Smart thermostat upgrade | +£150–£250 | Often bundled — check the deal |
What happens on the day
- 08:00 — dust sheets down, system drained, old boiler off the wall.
- Morning — new boiler hung on the existing pipe centres, new flue through the wall, condensate checked to a drain.
- Early afternoon — chemical flush, magnetic filter fitted, gas rate and pressures set.
- Late afternoon — commissioning, controls paired, Benchmark logbook signed, warranty and Building Regs registered.
Heating and hot water are typically back on the same evening. Conversions and relocations stretch to a second day.
Keeping the warranty valid
- Annual service (£80–£120) — miss one and most warranties void.
- Magnetic filter fitted and cleaned at each service.
- Installer registers the boiler with the manufacturer within 30 days — confirm before final payment.
- Keep the Benchmark logbook — it is the boiler’s service history when you sell.
Choosing the installer: checklist
- Verify the Gas Safe number on the official register — takes one minute.
- Manufacturer accreditation (e.g. Worcester Accredited, Vaillant Advance) unlocks the longest warranties.
- Itemised quote: model, output, flue parts, flush type, filter, controls.
- Three quotes on the same model — the spread is often £400+ for identical work.
FAQs
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