Boiler Replacement Cost
£1,800–£4,000
typical UK range
Updated
Replacing a boiler in the UK costs between £1,800 and £4,000 for most domestic properties, depending on the type of boiler, the complexity of the installation, and your location. A standard like-for-like combi replacement with a mid-range brand starts at around £1,800; a premium boiler on a complex conversion can reach £4,000+.
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How much does each option cost?
| Type / scope | Typical cost | Notes |
|---|---|---|
| Like-for-like combi swap (budget boiler)Simple replacement of an existing combi, same location, same flue route. Budget brands (Ideal, Baxi entry-level). Labour 4–6 hours | £1,500–£2,200 | Simple replacement of an existing combi, same location, same flue route. Budget brands (Ideal, Baxi entry-level). Labour 4–6 hours |
| Like-for-like combi swap (mid-range boiler)Replacement with Worcester Bosch Greenstar 4000 or Vaillant Ecotec Plus. Most common installation type. Includes magnetic filter | £1,900–£2,800 | Replacement with Worcester Bosch Greenstar 4000 or Vaillant Ecotec Plus. Most common installation type. Includes magnetic filter |
| Like-for-like combi swap (premium boiler)Worcester Bosch Greenstar 8000 or Viessmann Vitodens. Top-efficiency units with 10-year warranty potential via accredited installers | £2,400–£3,500 | Worcester Bosch Greenstar 8000 or Viessmann Vitodens. Top-efficiency units with 10-year warranty potential via accredited installers |
| System boiler with unvented cylinderSystem boiler plus a new unvented (pressurised) cylinder. Higher parts cost; cylinder installation adds 2–4 hours | £3,000–£5,500 | System boiler plus a new unvented (pressurised) cylinder. Higher parts cost; cylinder installation adds 2–4 hours |
| Combi conversion (back boiler removal)Removing an old back boiler or back boiler system and installing a combi. Includes decommissioning old unit and any new pipework runs | £2,500–£4,000 | Removing an old back boiler or back boiler system and installing a combi. Includes decommissioning old unit and any new pipework runs |
| New flue (non-standard route)When the flue cannot reuse the existing route — e.g. through a wall instead of roof, or extended flue run. Charged additionally | £200–£600 | When the flue cannot reuse the existing route — e.g. through a wall instead of roof, or extended flue run. Charged additionally |
| Power flushRecommended when installing a new boiler on an old, sludged system. Protects the new boiler and maintains warranty. Optional but advisable | £300–£500 | Recommended when installing a new boiler on an old, sludged system. Protects the new boiler and maintains warranty. Optional but advisable |
| Magnetic system filter (MagnaClean / Fernox)Fitted as standard by most installers; some include in the boiler price, others charge separately. Protects the boiler from magnetite sludge | £100–£200 | Fitted as standard by most installers; some include in the boiler price, others charge separately. Protects the boiler from magnetite sludge |
What affects the price?
- Type of boiler — combi, system, or heat-only. Combi (most popular) is usually the most cost-effective for properties with one bathroom. System boilers plus cylinders cost more but suit larger homes
- Boiler brand and specification — a budget Baxi or Ideal costs £300–£500 less than a mid-range Worcester Bosch; a Viessmann or Worcester 8000 adds £400–£800 over mid-range
- Complexity of the installation — a simple like-for-like replacement takes 4–6 hours; a conversion from a back boiler system with new pipework runs can take 2 days
- Location of the boiler — a standard kitchen or utility room installation is straightforward; an airing cupboard or loft conversion adds access difficulty and cost
- Whether the system needs a power flush — old, sludged systems should be flushed before a new boiler is fitted. Cost £300–£500 but protects the warranty and future efficiency
- Flue route — standard concentric flue through an external wall is cheapest; roof exits, extended flue runs, or non-standard routes add £200–£600
- Smart thermostat integration — adding a Nest, Hive, or manufacturer-brand smart thermostat typically adds £150–£350 to the installation cost
- Location in the UK — London and South East typically 20–40% above national average for the same installation
What's included in the price?
- Removal and disposal of the old boiler
- Supply and installation of the new boiler
- New flue terminal and flue components (for standard routes; non-standard may be additional)
- Connection to existing gas and water pipework
- Magnetic system filter (most reputable installers include this)
- Commissioning, testing, and flue gas analysis
- Gas Safe notification of the installation (legally required)
- Boiler manual and warranty registration
- Benchmark commissioning checklist (required for manufacturer warranty)
- Explanation of the new controls to the homeowner
How long does it take?
A standard like-for-like combi boiler swap takes 4–7 hours — most are completed within a single working day. The engineer will typically arrive in the morning, drain down the system, remove the old boiler, install the new unit, reconnect pipework, replace the flue, commission and test the boiler, and complete the Benchmark commissioning checklist before leaving. More complex installations (back boiler conversions, system boiler with cylinder, significant pipework changes) take 1–2 full days. You'll have no heating or hot water during the installation, so it's worth choosing a mild day if the timing is flexible.
Do I need one?
There's no legal obligation to replace a boiler at any specific age — but older, inefficient boilers can cost significantly more to run and are increasingly unreliable. A boiler over 12–15 years old, especially if it's a G-rated efficiency model (pre-2007), is worth replacing on running cost grounds alone. Modern condensing boilers operate at 92–95% efficiency compared to 70–80% for older non-condensing units — a saving of £150–£350 per year for many households at current gas prices. Replacement is urgently needed if your boiler is leaking gas or carbon monoxide, has been condemned by an engineer, or if the cost of repair exceeds 50% of a new installation.
How do you avoid overpaying?
- Get 3 quotes from Gas Safe registered engineers. Prices vary significantly for the same installation — £300–£600 differences are common for identical specifications
- Choose a mid-range brand rather than premium for budget installations — a Worcester Bosch Greenstar 4000 offers excellent reliability at a lower price point than the 8000 series
- Consider timing — spring and early summer are quieter for gas engineers and you may negotiate a better price. Winter emergency replacements command a premium
- Ask about manufacturer accreditation — an accredited installer (Worcester Bosch Accredited Installer, Vaillant Advance) can offer extended warranties (up to 10 years) that add long-term value
- Ask what's included in the quote — some quotes exclude the magnetic filter, power flush, or thermostat upgrade. Make sure you're comparing like-for-like before making a decision
- Bundle with an annual service contract — many engineers offer a small discount on the installation if you commit to annual servicing with them
- Check government schemes — the Boiler Upgrade Scheme provides £7,500 towards a heat pump if your property qualifies. ECO4 provides free boiler replacements for eligible low-income households
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Frequently asked questions
We’re happy to answer all your questions.
How much does it cost to replace a boiler in the UK?
Most domestic boiler replacements cost between £1,800 and £3,500 installed. The range depends on the type of boiler, brand, and complexity of the installation. A standard like-for-like combi swap with a mid-range brand typically costs £1,900–£2,800 in the UK (more in London).
How long does a boiler replacement take?
A standard like-for-like combi swap takes 4–7 hours and is usually completed in a single day. More complex installations (back boiler conversions, system boilers with new cylinders) can take 1–2 full days.
Should I get a combi or system boiler?
A combi boiler is best for smaller homes (1–2 bathrooms) with lower simultaneous hot water demand — it heats water on demand without a cylinder. A system boiler with an unvented cylinder suits larger homes with multiple bathrooms, providing higher flow rates and the ability to supply several hot water outlets simultaneously.
What is the most reliable boiler brand in the UK?
Worcester Bosch and Vaillant consistently top reliability surveys and have strong accredited installer networks in the UK. Viessmann is also highly regarded for quality and efficiency. Budget brands (Ideal, Baxi entry-level) are adequate but typically have lower efficiency ratings and shorter standard warranties.
Is there a grant for boiler replacement?
For low-income households, the ECO4 scheme (Great British Insulation Scheme) may provide a free or subsidised boiler replacement. The Boiler Upgrade Scheme provides £7,500 toward a heat pump installation (not a gas boiler). Check eligibility via the Simple Energy Advice website.
Do I need to be home during a boiler installation?
Yes — the engineer needs access to the boiler location, the gas meter, and usually various rooms for draining and checking radiators. You'll also need to be present at commissioning to confirm the controls are set correctly and sign off any documentation.
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