The short answer
A combi boiler replacement costs £1,500–£3,500 supply and fit for most UK homes in 2026. Budget brands start around £1,500 installed; mid-range from Worcester Bosch, Vaillant and Ideal sit between £2,200–£3,000; premium models with long warranties can reach £3,500 or more. For a full overview including system and regular boilers, see new boiler costs.
A combi replacement is the most common boiler job in the UK, and because millions of homeowners face it, the market is competitive — which can mean prices vary by £1,000 or more for the same boiler and a similar job. Understanding what is and is not included in a quote, and what genuinely drives the cost, puts you in a better position to compare estimates fairly.
Combi replacement costs at a glance
- Budget installed £1,500–£2,200
- Mid-range installed £2,200–£3,000
- Premium installed £3,000–£3,500+
- Typical labour £500–£900
- What’s included Boiler, flue, fitting, Gas Safe cert, Benchmark
- London premium 10–20% above UK average
What a combi replacement price covers
A properly quoted supply-and-fit price should include the boiler unit, the flue terminal, fitting and commissioning, a Benchmark Commissioning Checklist (the industry document proving the boiler has been correctly set up), and a Gas Safe certificate of installation. It should also include removal and disposal of the old boiler and flue parts. Some quotes also include a magnetic filter and inhibitor dose as standard; others price these separately at £80–£150. If a quote does not specify, ask. You should not pay for a Benchmark certificate separately — it is part of completing the job correctly and is required to validate the manufacturer’s warranty.
| Brand / tier | Boiler unit cost | Installed (supply & fit) | Typical warranty |
|---|---|---|---|
| Budget (e.g. Intergas, Alpha entry) | £600–£850 | £1,500–£2,000 | 2–5 years |
| Mid-range (Baxi, Ideal, Glow-worm) | £850–£1,200 | £2,000–£2,800 | 5–7 years |
| Premium (Worcester Bosch, Vaillant) | £1,100–£1,700 | £2,500–£3,500 | Up to 10 years (accredited install) |
What pushes the price up
Several factors can add to the base replacement cost. If the boiler is in an awkward location, in a loft or in a tight utility cupboard, labour time increases. If the existing flue is in poor condition or needs extending, materials add to the cost. If the gas meter or supply pipe is not capable of the new boiler’s demand, a gas supply upgrade is needed — this is relatively rare on modern supplies but can arise in older properties. Asbestos in the vicinity of the existing boiler requires specialist management before work begins. Any of these can add £200–£1,000 to the basic replacement figure, so a site visit or video survey before quoting matters.
- Non-standard flue route: longer runs, bends or rerouting — add £100–£400.
- Difficult location: loft, high wall or very tight space — add £100–£300.
- Gas supply upgrade: undersized meter or pipe — vary widely, consult engineer.
- Power flush: if the system is heavily sludged — typically £300–£500 extra.
- Magnetic filter: £80–£150 if not included in base price.
Brand warranties and their value
The warranty gap between budget and premium boilers is significant. A budget boiler with a 2–3 year warranty leaves you exposed to repair costs after year three; a premium boiler with a 10-year parts-and-labour warranty covers the most common failure modes over the boiler’s most productive years. Worcester Bosch and Vaillant both offer up to 10-year warranties through their accredited installer networks; this typically means the engineer must be registered with the manufacturer as well as Gas Safe, and the boiler must be commissioned and registered within 30 days of installation. The extra cost of a premium boiler with a long warranty can be worth it over a 10-year horizon, though it depends on the specific model’s reliability record. See our warranty guide for more detail.
Finance and grants
Many boiler installers offer 0% or low-rate finance plans, spreading the cost over 12, 24 or 36 months. If you are in a low-income household or claiming qualifying benefits, the ECO4 scheme may fund a partial or full replacement — see our boiler grants guide for eligibility. This is general information and typical costs are illustrations; your actual quote will reflect your specific boiler, property and location. All gas work must be done by a Gas Safe registered engineer.
Compare combi replacement quotes
Getting at least three quotes from Gas Safe registered engineers is the best way to ensure you pay a fair price for a properly specified installation.
Frequently asked questions
How much does it cost to replace a combi boiler?
A like-for-like combi boiler replacement typically costs £1,500–£3,500 supply and fit in 2026. The range reflects the boiler brand, output, your location and any additional work such as a magnetic filter or system flush.
Is it worth paying more for a Worcester Bosch or Vaillant?
For many homeowners, yes. Premium brands offer up to 10-year warranties through their accredited installer networks, and their boilers tend to have strong reliability records. The extra cost over a budget boiler may be recouped in avoided repair calls within 5–7 years.
What is included in a boiler replacement quote?
A properly itemised quote should include the boiler unit, flue, fitting, commissioning (Benchmark Checklist), Gas Safe certificate and removal of the old boiler. Some quotes also include a magnetic filter, inhibitor and an annual service. Always check what is and is not included before comparing prices.
How long does a combi boiler replacement take?
A straightforward like-for-like combi replacement typically takes 4–8 hours, so most installations are completed in one day. More complex jobs — involving a power flush, pipework changes or boiler relocation — may take two days.
Sources & further reading
- Gas Safe Register — installer registration and installation guidance
- Energy Saving Trust — boiler replacement and energy efficiency
- GOV.UK — ECO4 scheme and Boiler Upgrade Scheme eligibility
- HHIC — Heating and Hotwater Industry Council, boiler pricing and consumer guidance
This is general information, not advice for your specific property or installation. Costs, timescales and outcomes vary with your home, system condition and chosen engineer. All gas boiler work must be carried out by a Gas Safe registered engineer.