Boiler Replacement Cost UK
Updated 24 March 2026
Full breakdown by boiler type, property size, and what is included. Combi, system, regular, and back boiler costs compared.
Quick Answer
- New combi boiler installed: £1,800 to £3,500
- System boiler: £2,000 to £4,000
- Back boiler replacement: £2,500 to £5,000
Price depends on boiler type and the complexity of the swap. Switching from a regular or back boiler to a combi adds pipework costs.
Cost by Boiler Type
All prices include supply of the new boiler, labour, and removal of the old unit.
Combi Boiler
Most popular£1,800 to £3,500
Heats water on demand with no need for a hot water tank or cold water cistern. Ideal for flats and smaller homes. The simplest installation when replacing an existing combi.
System Boiler
£2,000 to £4,000
Works with a hot water cylinder (stored in an airing cupboard). Good for homes with multiple bathrooms where hot water demand is high. No cold water tank needed in the loft.
Regular (Heat-Only) Boiler
£2,000 to £4,500
Needs both a hot water cylinder and a cold water storage tank in the loft. Usually a like-for-like swap in older homes that already have this setup. Higher costs if the tanks need replacing too.
Back Boiler Replacement
Most complex£2,500 to £5,000
Removing a back boiler behind a gas fire and installing a modern combi involves extra work: removing the fire surround, decommissioning the old unit, routing new pipework, and cutting a new flue. Job takes 2 to 3 days.
Combi vs System vs Regular Boiler
Choosing the right boiler type affects both upfront cost and long-term running costs.
| Feature | Combi | System | Regular |
|---|---|---|---|
| Hot water tank | Not needed | Required | Required |
| Loft tank | Not needed | Not needed | Required |
| Best for | Flats, 1-3 bed homes | 3+ bed, 2+ bathrooms | Large older homes |
| Install time | 1 day | 1 to 2 days | 1 to 2 days |
| Typical cost | £1,800 to £3,500 | £2,000 to £4,000 | £2,000 to £4,500 |
What Is Included in the Price?
A standard boiler replacement quote should cover these items. Check what is and is not included before accepting any quote.
Boiler unit
£600 to £1,500Budget brands (Ideal, Baxi) are cheaper. Premium brands (Worcester Bosch, Vaillant) cost more but often carry longer warranties.
Installation labour
£500 to £1,500Typically 1 to 2 days for a like-for-like swap. Switching boiler type or moving the boiler location adds cost.
Flue and fittings
£100 to £300The flue exhausts gases outside. A standard horizontal flue is cheapest; vertical flues or longer runs cost more.
Powerflush
£300 to £500Cleans sludge and debris from the heating system. Strongly recommended for older systems. Some installers include it; others charge separately.
Controls and thermostat
£100 to £300Basic programmers are cheap. Smart thermostats (Nest, Hive, Tado) cost more but can reduce bills. Some boilers include a basic controller.
Building Regs notification
£100 to £200Gas Safe registered engineers notify building control automatically. This certificate is required and should always be included in the quote.
Cost by Property Size
Larger homes need higher-output boilers, which cost more. These are typical all-in prices for a straightforward replacement.
| Property | Recommended boiler | Typical cost |
|---|---|---|
| 1-bed flat | 24kW combi | £1,800 to £2,500 |
| 2-bed terrace | 24-28kW combi | £1,900 to £2,800 |
| 3-bed semi | 28-30kW combi | £2,000 to £3,000 |
| 4-bed detached | 35kW combi or system | £2,500 to £4,000 |
| Large house (5+ bed) | System boiler + cylinder | £3,000 to £5,000 |
Prices are for like-for-like swaps. Switching boiler type or relocating the boiler adds £300 to £1,000 for pipework changes.
Boiler Grants and Schemes
Government schemes can significantly reduce or eliminate the cost of a boiler replacement for eligible households.
ECO4 Scheme
Free boiler possibleProvides free or heavily subsidised boiler replacements for low-income households and those receiving certain benefits (Universal Credit, Pension Credit, ESA, and others). Funded by energy companies.
- Covers full installation in many cases
- Available through energy suppliers
- Eligibility based on income and benefits
Boiler Upgrade Scheme
£7,500 grantProvides a £7,500 grant toward an air source heat pump. Not for gas boiler replacements, but worth considering if you are looking at low-carbon heating options. Available in England and Wales.
- For heat pumps only, not gas boilers
- Applied by the installer, not the homeowner
- Check eligibility at gov.uk
How to check eligibility
Visit gov.uk/energy-company-obligation for ECO4 and gov.uk/apply-boiler-upgrade-scheme for the Boiler Upgrade Scheme. You can also contact your energy supplier directly about ECO4 funding.
Frequently Asked Questions
How much does a new combi boiler cost to install in the UK?
A new combi boiler installed typically costs £1,800 to £3,500 including supply, labour, and removal of the old unit. Budget models from Vaillant or Worcester Bosch start around £1,800 for a 1 to 2 bed flat, while premium 35kW models for larger homes reach £3,500.
Is a back boiler replacement more expensive?
Yes. Replacing a back boiler with a modern combi costs £2,500 to £5,000. The extra cost comes from removing the back boiler unit and fire surround, rerouting pipework, and fitting a new flue through an external wall. The job typically takes 2 to 3 days.
What grants are available for boiler replacement in the UK?
The ECO4 scheme offers free or heavily subsidised boiler replacements for qualifying households on certain benefits or low incomes. The Boiler Upgrade Scheme provides a £7,500 grant toward an air source heat pump. Check eligibility at gov.uk.
Do I need a powerflush when replacing a boiler?
Most installers recommend a powerflush on older systems to remove sludge and debris. It costs £300 to £500 and extends boiler life significantly. Without it, debris from old pipework can damage the new boiler heat exchanger within a few years.