How much does a new boiler cost?
Quick answer: Swapping a gas combi boiler for a new one usually costs £1,900–£3,800 fitted. Converting a system or regular boiler to a combi costs £3,000–£5,700. There's no government grant for gas boilers, but you can get £7,500 towards a heat pump.
Work out your cost
Choose what you need. We'll show a typical price range and how it's made up.
Typical prices, job by job
| Job | Typical price | How long | Notes |
|---|---|---|---|
| Combi, like-for-like swap | £1,900–£3,800 | 1 day | Median quote about £2,300. |
| System or regular to combi | £3,000–£5,700 | 1.5–2 days | Removes the tanks and cylinder. |
| System boiler | £1,800–£4,800 | 1–2 days | Higher if the cylinder needs replacing. |
| Regular (heat-only) boiler | £1,800–£3,900 | 1 day | |
| Back boiler conversion | £3,500–£6,000 | 2–3 days | Single source, treat as a guide. |
| Powerflush | £400–£800 | 3–9 hrs | Depends on the number of radiators. |
| Magnetic filter | £100–£260 | 1 hr | Often included with a new boiler. |
| New or extended flue | £120–£600 | included | Vertical flues cost more. |
| Moving the boiler | £500–£1,000 | +1 day | |
| Smart thermostat | £150–£300 | 1–2 hrs | |
| Air source heat pump grant | £7,500 off | 2–5 days | Boiler Upgrade Scheme, England and Wales. |
Expect to pay about 20% more in London and 10% more in the South East than in the Midlands, and slightly less in the North.
How to keep the cost down
- Keep the boiler in the same place to avoid relocation costs.
- Get at least three quotes that list what's included: filter, flush and controls.
- Book in late spring or summer, when heating engineers are less busy.
- A longer warranty is worth more than the cheapest unit.
- Check if you qualify for the £7,500 heat pump grant before replacing a gas boiler.
Comparing quotes
- Get two or three written quotes that cover the same work.
- Check what's included and what's extra, including materials and clearing up.
- Ask about insurance, guarantees and any registration the work needs.
- Agree payment stages. Avoid paying a large deposit up front.
- Read recent reviews. On Seconded, every review comes from a confirmed job.
Common questions
How long does it take to fit a new boiler?
A combi swap usually takes one day. A conversion or moving the boiler takes 1.5–3 days.
Is there a grant for a new gas boiler?
Not under the Boiler Upgrade Scheme, which only covers heat pumps (£7,500) and biomass boilers (£5,000). Some lower-income households can get help through ECO4.
Do I need a powerflush?
Only if your system has a lot of sludge. Many installers include a chemical flush, and some manufacturers ask for one to honour the warranty.
Which boiler brand is best?
The quality of the installation and the length of the warranty matter more than the badge. Look for a 7–12 year warranty.
Should I switch to a combi?
Usually yes for small and medium homes with one bathroom. Homes with several bathrooms often suit a system boiler better.
Who can fit a gas boiler?
Only a Gas Safe registered engineer. Ask to see their ID card.