A straight combi swap in the same spot typically runs about £1,800–£3,000 fitted; a full system change or a relocation can push past £4,000 (rough 2026 figures that vary by brand and area). The biggest price movers: the boiler make and size, whether you move it, and extras like a power flush or new flue.
The ballpark, by job type
Boiler jobs vary massively depending on whether you're swapping like-for-like or changing the whole system. These are illustrative 2026 UK ranges including boiler and labour, not a fixed price list — brand, output, area and site conditions move them.
| Scenario | Price range (approx) |
|---|---|
| Straight combi swap, same location | £1,800–£3,000 |
| Combi swap + move to a new spot | £2,800–£4,000 |
| Conventional to combi conversion | £3,500–£5,000 |
| New system/regular boiler + cylinder | £3,500–£6,000+ |
The boiler itself is a big chunk of that — a budget unit and a premium one (Worcester, Vaillant and the like) can be £900 apart before you've turned a spanner, and the longer warranties usually ride on the pricier brands.
What actually moves the price
Three things, mostly. The boiler — brand, output and warranty. The location — leaving it where it is is quick; moving it means new gas, water and flue runs, and often making-good afterwards. And the system — a like-for-like combi swap is a day's work for a good team, while ripping out a tank-and-cylinder setup and converting to a combi is a different animal. Then the extras stack up: a magnetic filter (fit one — it protects the job and your callbacks), a power flush or chemical flush if the system's sludged, new controls or a smart thermostat, and TRVs.
Day rate vs fixed price
Most boiler installs go out as a fixed price with the boiler and parts itemised, but the labour behind it is day-rate maths — a Gas Safe engineer's day rate in 2026 sits roughly £250–£400 (approximate and area-dependent). Price the days honestly. A "one-day" swap that turns into two because the old pipework's a mess is how a tight quote goes underwater. More on what belongs on the quote — and TradePA writes it from a voice note while you're still in the van, for £10 a month with two weeks free.
Don't leave these off the quote
The power flush is the big one — if the system needs it and you didn't quote it, you're either eating £300–£600 (approx) or having an awkward conversation. Same with a new flue, scaffolding if the flue's high up, an upgraded gas supply pipe, and Building Regs notification. Old flues can mean asbestos, which is a specialist cost, not a maybe. Register the warranty and put it on the quote — it's a genuine selling point, so charge like it matters. If it's a rental, the landlord will want a CP12 gas safety record too — separate job, separate line on the invoice.
Honest note: these are illustrative 2026 ballparks, not a quote and not financial advice. Prices vary by boiler, property and region — survey the actual system before you price it.
Common questions
How much should I charge for a combi boiler swap?
Do I need to include a power flush in the quote?
What's a fair day rate for a gas engineer in 2026?
Why do two boiler quotes for the same house differ so much?
A word on the above. This is general information for UK trades, written to be useful, not advice for your situation. Prices vary by job and by region, and tax and legal rules change. Check the current position on GOV.UK or ask your accountant or legal professional for actual advice.
