Boiler Replacement Cost UK 2026: Combi, System & Heat Pumps
A new boiler is one of the biggest single home-services bills most UK homeowners ever pay — and one of the most marked-up. National installer chains can be 30–50% more expensive than a local Gas Safe engineer doing the exact same job. Here's what's reasonable to pay in 2026.
Average new boiler cost in the UK (2026)
| Boiler type | Boiler unit | Total fitted price |
|---|---|---|
| Combi (like-for-like swap) | £800 – £1,800 | £1,800 – £2,800 |
| Combi (relocation or upsize) | £900 – £2,000 | £2,500 – £4,000 |
| System boiler + cylinder | £1,000 – £2,200 | £2,500 – £3,800 |
| Regular boiler (heat-only) | £900 – £1,800 | £2,200 – £3,500 |
| Conventional → combi conversion | £900 – £1,800 | £3,000 – £4,500 |
| Air source heat pump (pre-grant) | £3,500 – £6,500 | £8,000 – £14,000 |
| Air source heat pump (after BUS grant) | — | £500 – £6,500 net |
Combi boiler swap: what fair pricing looks like
A like-for-like combi swap is the simplest, cheapest replacement: same location, same flue route, same gas pipe size. In 2026, expect £1,800–£2,800 for a 1-day install with a mid-range Worcester Bosch, Vaillant or Ideal boiler. Premium models (Viessmann 200-W, Worcester 8000) push the upper end to £3,000–£3,500.
Where the price genuinely changes:
- Flue extension — every additional metre adds roughly £40–£70
- Gas pipe upgrade — bigger combis often need 22mm or 28mm gas, which can mean lifting floors (£200–£600 extra)
- Magnetic system filter — should always be included; if it's not on the quote, ask for it
- Power flush — needed if the system is silted up. Adds £350–£600 but protects the warranty
- Chemical inhibitor — non-negotiable, but should be in the base price
System and regular boiler replacements
If you have a hot water cylinder and (sometimes) a tank in the loft, you have a system or regular boiler — common in larger UK homes with multiple bathrooms. Replacing one like-for-like is £2,200–£3,800 fitted. A typical 1.5–2 day install includes the boiler, expansion vessel, and central heating commissioning. Many homeowners take this opportunity to also replace the cylinder (£700–£1,300 extra) which can transform hot water performance.
Converting from conventional to combi
Switching from a conventional (regular) system to a combi means removing the cylinder and tanks, re-routing pipework and (usually) a gas pipe upgrade. Expect £3,000–£4,500 fitted for a typical 3-bed house. It's only worth doing if your mains water pressure is decent — combis don't perform well below 1.5 bar dynamic pressure.
Heat pumps: 2026 reality check
Air source heat pumps are no longer niche — over 60,000 UK installations completed in 2025. Typical installed cost in 2026 is £8,000–£14,000 before the Boiler Upgrade Scheme grant. With the £7,500 BUS grant, net cost falls to roughly £500–£6,500 — putting heat pumps in the same ballpark as a premium boiler install.
What inflates the price beyond a basic install:
- Radiator upgrades — heat pumps run at lower temperatures, so you often need bigger radiators. Adds £700–£2,500.
- Hot water cylinder — required for heat pumps. £900–£1,800 fitted.
- Insulation — heat pumps work best in well-insulated homes. Topping up loft and cavity insulation pays back fast.
- Buffer tank — required on some installations, adds £400–£900.
Boiler warranties (and how to keep them valid)
Manufacturer warranties have got generous in 2026 — Worcester Bosch's 8000 Style range is up to 12 years, Vaillant ecoTEC plus is 10 years, Viessmann 200-W is 10 years, and Ideal Logic Max is up to 10 years. All warranties require annual servicing by a Gas Safe engineer and proof of correct installation (system flush, magnetic filter, inhibitor). Skip an annual service and the warranty is dead.
National installer vs local Gas Safe engineer
Big-name national installers (BOXT, British Gas, Heatable etc.) typically quote 20–50% more than a local Gas Safe engineer for the same job. The premium pays for the brand, the call-centre and the national field force — not for better engineering. The actual install is usually done by a local subcontractor anyway.
A local Gas Safe engineer who runs a small business has a reputation to protect, will usually answer their phone for years afterwards, and will often offer extended labour warranties to compete with the big firms.
How to genuinely save money on a boiler install
- Get three quotes from local Gas Safe engineers — not just from national online quote tools.
- Stick with the brand of boiler your engineer fits most often. They'll have the parts, the manufacturer relationship and the warranty registration sorted.
- Don't oversize. Bigger isn't better — the right kW output saves you cycling losses and replacement costs.
- Time it well. Boiler engineers are busiest October–February. Booking a non-urgent swap in May or June can drop the price 5–15%.
- Ask about 0% finance — most engineers offer it for installs over £2,000, and it's usually genuinely 0%.
Frequently asked questions
How much does a new combi boiler cost fitted in the UK?
A like-for-like combi boiler swap costs £1,800–£2,800 fitted in the UK in 2026. Premium boilers (Viessmann 200-W, Worcester 8000) and relocated installs push the price to £3,000–£4,000. The price should always include the flue, system filter, chemical flush, commissioning and Building Control notification.
How long does a boiler installation take?
A like-for-like combi swap takes 1 working day. System and regular boiler replacements take 1–2 days. A conventional-to-combi conversion is typically 2 days. Heat pump installations take 2–4 days, plus separate radiator upgrade days if needed.
Are heat pumps worth it in 2026?
After the £7,500 Boiler Upgrade Scheme grant, heat pumps cost £500–£6,500 net to install in the UK in 2026 — broadly similar to a premium gas boiler. Running costs depend on your home's insulation and electricity tariff, but well-insulated homes with a heat pump tariff typically see annual running costs comparable to or better than gas.
Should I replace my boiler with a combi or stick with a system boiler?
Stick with system if you have multiple bathrooms in regular simultaneous use, or if your mains water pressure is below 1.5 bar dynamic. Switch to combi if you have a 1–2 bathroom home, decent mains pressure, and want to free up the airing cupboard and loft space.
Why do national installers quote so much more than local engineers?
National brands carry call-centre, marketing and field-force overheads — typically 20–50% more than a local Gas Safe engineer for the same install. The actual fitter is usually a local subcontractor regardless. Local engineers booked through a marketplace like AllSorted give you the same Gas Safe certification and similar warranty terms at lower cost.
Do I need to replace my radiators when I get a new boiler?
Not for a like-for-like gas boiler swap — modern combis work fine with existing radiators. For a heat pump, you'll often need 2–4 larger radiators because of the lower flow temperature. A reputable engineer will do a heat-loss calculation before quoting and tell you which (if any) need upsizing.
About the author
AllSorted Editorial Team
Home services research & UK trades industry analysis
The AllSorted Editorial Team works with verified UK tradespeople, plumbers, electricians and home services professionals to publish accurate, up-to-date guidance for British homeowners. Editorial standards are reviewed against guidance from the Federation of Master Builders, NICEIC, Gas Safe Register and Trading Standards.