How much does a new boiler cost in the UK?
A new combi boiler installed in the UK typically costs £1,800–£3,500 including a standard installation. System and heat-only boilers cost slightly more due to additional components.
| Type | Supply & fit cost |
|---|---|
| Budget combi boiler | £1,500–£2,200 |
| Mid-range combi boiler | £2,200–£3,000 |
| Premium combi boiler | £3,000–£4,500 |
| System boiler (+ cylinder) | £2,500–£4,500 |
| Heat-only boiler (+ cylinder) | £2,500–£5,000 |
These prices assume a straightforward like-for-like replacement. Additional costs apply for flue extensions, magnetic filter installation, inhibitor dosing, and powerflush if required.
Best boiler brands in 2026
Worcester Bosch — consistently rated the UK's most reliable boiler brand. Their Greenstar range offers 8–12 year warranties and a strong engineer network. Slightly premium priced but worth the investment for most homes.
Viessmann — German engineering with excellent efficiency ratings. The Vitodens range is popular in the premium sector. Viessmann engineers are well-trained and the spare parts supply is reliable.
Vaillant — another strong European brand with a wide installer network and good warranty terms. The ecoTEC range is a popular mid-range choice.
Baxi — solid value for money, widely available, good parts supply. Popular with installers for budget-conscious customers.
Ideal — a UK manufacturer based in Hull. The Logic range is reliable and competitive on price. Good for rental properties and budget installations.
Alpha — budget-friendly, widely available, but shorter warranty periods and higher ongoing maintenance costs than premium brands.
What affects the cost of a boiler replacement?
- Boiler type: Combi boilers are the most popular and cheapest to install (no cylinder needed). System and heat-only boilers require a hot water cylinder, adding £200–£800 for the cylinder plus installation labour.
- Flue changes: If the new boiler can't use the existing flue position, extending or re-routing the flue adds £150–£400.
- Magnetic filter: A magnetic filter (Magnaclean or Fernox) extends boiler life by removing sludge. Cost: £80–£150 fitted. Some installers include this; others don't.
- Powerflush: If your radiators are cold at the bottom, the system may need a powerflush to remove sludge before the new boiler is fitted. Cost: £300–£600 for a typical house.
- Moving the boiler: Relocating a boiler to a different room (e.g., loft to kitchen) can add £300–£800 for new pipework and flue.
- Asbestos: In older properties, flue pipes may contain asbestos. Removal is a specialist job and adds significant cost.
Why you must use a Gas Safe registered engineer
Gas boiler installation in the UK must be carried out by a Gas Safe registered engineer. This is a legal requirement, not a recommendation.
Installing or altering a gas appliance without Gas Safe registration is illegal and invalidates your home insurance. If something goes wrong (gas leak, carbon monoxide escape), you could face criminal liability.
Always:
1. Verify your engineer's Gas Safe ID before they start work. You can check registration at gassaferegister.co.uk or ask to see their card (it lists which appliances they're qualified to work on).
2. Ask for a Gas Safe Certificate (formerly CORGI certificate) on completion.
3. Never let a plumber or handyman without Gas Safe registration touch your boiler or gas pipes, no matter how trusted they are.
When should you replace your boiler?
Boilers typically last 10–15 years with annual servicing. Signs it's time to replace:
- Age over 12 years: Efficiency has likely degraded significantly. Modern A-rated boilers are 25–30% more efficient than a 15-year-old G-rated model.
- Increasing repair costs: If you're spending £200–£400/year on repairs, a new boiler will often pay for itself within 3–5 years.
- Persistent pressure problems: Frequently needing to repressurise the system suggests a failing pressure vessel or seals.
- Yellow or orange flame: Should be blue. Yellow indicates incomplete combustion and a carbon monoxide risk — switch off and call a Gas Safe engineer immediately.
- Rising energy bills: A deteriorating boiler runs less efficiently. An A-rated replacement could cut heating costs by £150–£350/year.
- Parts no longer available: For older boilers, spare parts can become unavailable, making repair impossible.
Finding a Gas Safe boiler engineer
- Check Gas Safe registration: Always verify before booking, not after.
- Get 3 quotes: For a standard combi replacement, you should get itemised quotes including boiler model, warranty terms, and what's included (filter, inhibitor, certificate).
- Check for grants: The government's Great British Insulation Scheme and local authority schemes may subsidise boiler replacement for eligible households (fuel poverty, old inefficient boilers). Check gov.uk for current schemes.
- Annual servicing: Budget £80–£120/year for an annual boiler service. This is a condition of most boiler warranties and extends the boiler's life significantly.
- Boiler finance: Many Gas Safe engineers offer 0% or low-rate finance for boiler replacement. Compare the total cost carefully against paying upfront.