Updated 25 September 2026
Combi boiler swap cost UK 2026
The going rate for combi boiler swap in 2026 is £2,150–£3,000 (total, ex VAT). Below: a calculator, what the job involves, materials at three price levels, and the prep that changes the price.
Market band£2,150–£3,000
Worked example, 1 boiler£2,327
Time on site1 days
Combi boiler swap calculator
Price a real job freeUses your rates, your speed and your receipts.
Market band source: Heatable.
What the job involves
| Stage | Task | Typical time |
|---|---|---|
| out | Drain down and remove old boiler | 2 h |
| in | Fit boiler, flue and controls | 5 h |
| in | Chemical cleanse, filter, inhibitor, commission | 2 h |
Materials at three price levels
| Material | Budget | Trade choice | Premium |
|---|---|---|---|
| Combi boiler (A-rated, 25–30 kW) each | £750 Entry combi, 7-year warranty — Lowest cost compliant boiler | £1,000 Mid-range combi, 10-year warranty — Reliable, parts easy to get | £1,500 Premium combi, 12-year warranty — Quieter, better hot water |
| Magnetic filter and cleanser each | £90 Basic magnetic filter — Catches sludge | £130 Branded filter and cleanser — Protects the heat exchanger | £180 Dual-action filter — Best protection |
| Flue kit each | £60 Standard horizontal flue — Straight out the wall | £90 Telescopic flue — Fits the wall thickness | £120 Vertical or plume management kit — Awkward terminal positions |
| Heating controls each | £40 Wired programmable stat — Meets Part L controls | £80 Wireless programmable stat — Place it anywhere | £180 Smart thermostat — App control |
| Valves, pipe, fittings and condensate allowance | £50 Standard fittings — Connects up | £80 Fittings plus frost-protected condensate — No frozen condensate | £120 Full copper tails and lagging — Tidy, efficient |
Trade prices ex VAT, estimates checked 2026-09-25. Log your receipts in Grafto and your own prices replace these.
What changes the price
- Boiler staying in the same place? same place · moving big effect
- Controls? keep existing · new programmable stat · smart controls
- Gas pipe size OK? yes - 22 mm · no - needs upsizing · not checked big effect
Good practice
- Gas supply must be sized for the new boiler
- Moving the boiler adds flue, gas and condensate runs
Prep to look for
| Condition | Check | Effect |
|---|---|---|
| Sludge in the system | black water from a bleed valve, radiators cold at the bottom | Power flush the system |
| Microbore pipework | 8–10 mm pipes to radiators | Microbore: limits radiator upgrades and blocks easily — flush it |
| Boiler age from badge | data badge or model label on the boiler | Check the boiler age on the badge: over 12–15 years, replace rather than repair |
| Corroded fittings | green or white crust, rust on valves and pipes | Replace corroded valves |
| Possible asbestos lagging | old grey or white pipe lagging | Possible asbestos lagging: stop and test before disturbing |
Questions
How much does combi boiler swap cost in the UK in 2026?
The researched market band is £2,150–£3,000 (total, ex VAT), from Heatable. A worked example of 1 boiler comes to about £1,810–£3,281 across budget, trade and premium materials.
How long does combi boiler swap take?
The worked example of 1 boiler takes about 1 working days.
What changes the price of combi boiler swap?
Mainly boiler staying in the same place, gas pipe size ok, plus any prep found on site: sludge in the system, microbore pipework, boiler age from badge, corroded fittings.