New Boiler Cost UK 2026
How much does a new boiler cost in the UK? Combi, system, and regular boiler prices with a full breakdown of supply, installation, and additional work such as flue runs, pipework, and controls.
For homeowners needing a new boiler and Gas Safe engineers quoting them
Last updated: May 2026
Replacing a boiler is one of the most common — and most essential — home improvement jobs in the UK. The average gas boiler lasts 12–15 years, and by that point efficiency has dropped, parts become harder to source, and the risk of a mid-winter breakdown increases significantly. A modern condensing boiler runs at 90–94% efficiency compared with 70–80% for older models, which typically saves £200–£400 per year on gas bills.
This guide covers the realistic 2026 cost of a new gas boiler across the UK, including combi, system, and regular (heat-only) boilers. We also cover the cost of moving a boiler, converting from one type to another, and the additional work that commonly arises during a boiler replacement. All work must be carried out by a Gas Safe registered engineer.
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Summary Cost Table
| Work | Typical Cost (2026) |
|---|---|
| Combi boiler (like-for-like swap) | £1,800 – £3,500 |
| System boiler (like-for-like swap) | £2,200 – £4,000 |
| Regular boiler (like-for-like swap) | £2,000 – £3,800 |
| Combi boiler (relocating to new position) | £2,500 – £4,500 |
| Converting regular/system to combi | £2,800 – £5,000 |
| Power flush (existing system) | £400 – £600 |
| Magnetic filter (MagnaClean) | £120 – £200 |
| New controls and thermostat | £150 – £500 |
| Unvented hot water cylinder | £1,000 – £2,000 |
Prices include supply, installation, and VAT. London and the South East are typically 10–25% higher than the national average. Scotland, Wales, and the North of England tend to sit at the lower end of each range.
Detailed Cost Breakdown
Boiler Supply — Brand Comparison
The boiler itself typically accounts for 50–60% of the total cost. Here are the major brands available in the UK market:
| Brand | Combi (supply only) | Warranty |
|---|---|---|
| Worcester Bosch (Greenstar 4000/8000) | £900 – £1,800 | Up to 12 years |
| Vaillant (ecoTEC plus/exclusive) | £850 – £1,600 | Up to 10 years |
| Ideal (Logic+ / Vogue) | £650 – £1,200 | Up to 12 years |
| Baxi (800 / Platinum+) | £600 – £1,100 | Up to 10 years |
| Viessmann (Vitodens 050/100) | £800 – £1,500 | Up to 12 years |
Worcester Bosch and Vaillant are the two most popular brands in the UK and together account for over 50% of the domestic market. Both offer reliable performance and strong warranty terms. Ideal and Baxi are excellent budget-to-mid-range options. Viessmann is a German premium brand that has grown rapidly in the UK market.
Installation Labour
Labour for a boiler installation depends on the complexity of the job. A straightforward like-for-like swap is the cheapest option.
- Like-for-like combi swap (same position, same type) — £500 – £900 labour
- Like-for-like system or regular swap — £600 – £1,000 labour
- Relocating boiler to a new position — £800 – £1,500 labour (additional pipework and flue run)
- Converting from regular to combi — £800 – £1,500 labour (removing tanks, cylinder, re-routing pipework)
- Gas Safe certificate and notification — included in all installations
A like-for-like swap typically takes one day. Relocating a boiler or converting from one type to another can take 1.5–2 days due to additional pipework, flue routing, and the removal of old components.
Flue and Gas Supply
- Standard horizontal flue (through external wall) — included in most quotes
- Extended flue run (up to 3 metres) — £100 – £300
- Vertical flue (through roof) — £250 – £500
- Plume management kit — £80 – £150 (required if the flue terminates near a window, door, or boundary)
- Gas pipe upgrade (15mm to 22mm) — £100 – £300
Controls and Thermostats
Modern building regulations require a programmer, room thermostat, and thermostatic radiator valves (TRVs) as a minimum. Smart thermostats are an increasingly popular upgrade.
- Basic programmer and room thermostat — £100 – £200
- Smart thermostat (Hive, Nest, tado) — £200 – £350 supply and fit
- Thermostatic radiator valves (per valve) — £15 – £30 supply and fit
- Full set of TRVs (3-bed house, ~8 radiators) — £120 – £240
- Weather compensation kit — £150 – £350
System Cleaning and Protection
A power flush is strongly recommended when installing a new boiler on an existing heating system. It removes sludge, rust, and debris that would otherwise damage the new boiler and reduce its efficiency.
- Power flush (full system, 8–10 radiators) — £400 – £600
- Magnetic filter (MagnaClean or similar) — £120 – £200
- Chemical inhibitor dose — £30 – £50 (typically included)
Most boiler manufacturers now require evidence of a system flush and the installation of a magnetic filter to validate the warranty. Skipping a power flush can void a 10-year warranty from day one.
Hot Water Cylinders
If you are installing or replacing a system boiler, you will need a hot water cylinder. Unvented cylinders (mains-pressure hot water) are the modern standard.
- Vented cylinder (gravity-fed, copper) — £300 – £600 supply and fit
- Unvented cylinder (mains-pressure, 150–210L) — £1,000 – £2,000 supply and fit
- Megaflo / Heatrae Sadia (premium brands) — £1,200 – £2,200 supply and fit
Unvented cylinders must be installed by a G3-qualified engineer. They provide mains-pressure hot water to all outlets simultaneously, eliminating the need for a cold water tank in the loft.
Radiator Upgrades
- Single radiator replacement (standard panel) — £150 – £300 supply and fit
- Full house radiator upgrade (3-bed, ~8 radiators) — £1,200 – £2,400
- Designer or vertical radiator (per unit) — £250 – £600 supply and fit
- Towel rail (bathroom) — £150 – £350 supply and fit
Factors That Affect Cost
- Boiler type — combi boilers are the cheapest to install because they require no cylinder or tanks. System boilers cost more due to the cylinder. Regular boilers need both a cylinder and header tanks.
- Like-for-like vs conversion — swapping combi for combi in the same position is the cheapest job. Converting from a regular boiler to a combi involves removing the hot water cylinder, cold water tanks, and associated pipework.
- Boiler location — moving a boiler to a new room requires extending gas, water, and waste pipes plus a new flue run, adding £500–£1,500 to the job.
- System condition — old systems with sludge and debris need a power flush before a new boiler can be safely connected. This adds £400–£600 but protects the warranty.
- Property size — larger houses need higher-output boilers (35kW+ combi or 25kW+ system with a large cylinder), which cost more to buy.
- Flue routing — if the boiler cannot vent directly through an adjacent external wall, extended or vertical flue runs add cost.
- Location — London and the South East are 10–25% higher than the national average for installation labour.
How Long Does It Take?
| Job | Duration |
|---|---|
| Like-for-like combi swap | 1 day |
| Like-for-like system or regular swap | 1 – 1.5 days |
| Relocating boiler to new position | 1.5 – 2 days |
| Converting regular to combi | 1.5 – 2 days |
| Power flush (add-on) | 4 – 6 hours |
Most boiler installations are completed within a single day. You will be without heating and hot water during the installation, so avoid scheduling during the coldest months if possible. If the job runs into a second day, the engineer will typically leave the heating system operational overnight.
How to Save Money
- Stick with a like-for-like swap — keeping the boiler in the same position and the same type avoids additional pipework, flue runs, and removal of old components. This is consistently the cheapest option.
- Compare at least three quotes — boiler installation prices vary significantly between Gas Safe engineers. Get itemised quotes that break out the boiler cost, labour, and ancillary work separately.
- Choose a mid-range brand — Ideal and Baxi offer excellent reliability and warranty terms at £200–£400 less than Worcester Bosch or Vaillant for comparable output.
- Buy during the summer — Gas Safe engineers are quietest from May to September. Some offer 5–15% discounts or throw in extras like a smart thermostat or magnetic filter.
- Check for grants — the ECO4 scheme provides free or subsidised boiler replacements for qualifying households (low income, poor EPC rating). Contact your energy supplier to check eligibility.
- Consider a 0% finance deal — many boiler companies offer 0% finance over 2–5 years, spreading the cost without interest. Worcester Bosch and Vaillant both run installer finance schemes.
Common Questions
The average gas boiler lasts 12–15 years with annual servicing. Some well-maintained boilers run for 20 years, but efficiency declines over time and parts become harder to source after 10–12 years. If your boiler is over 10 years old and requiring frequent repairs, replacement is usually more economical than continued maintenance.
For a combi boiler: a 1–2 bedroom flat needs 24–28kW; a 3-bedroom semi needs 28–34kW; a 4+ bedroom house with two bathrooms needs 35kW or a system boiler with an unvented cylinder. The key factor for combis is hot water flow rate — larger homes with multiple bathrooms benefit from a system boiler because it can supply several outlets simultaneously from the stored cylinder.
A combi is ideal for small to medium homes (up to 3 bedrooms, 1 bathroom) because it heats water on demand and requires no cylinder or tanks. A system boiler with an unvented cylinder is better for larger homes with two or more bathrooms, because it stores a volume of hot water that can supply multiple outlets at once without a drop in pressure or temperature.
It is strongly recommended, especially if the existing system is more than 10 years old. A power flush removes sludge, rust, and magnetite that would otherwise clog the new boiler's heat exchanger and reduce efficiency. Most manufacturers now require evidence of a system flush and magnetic filter to validate their warranty — skipping it can void a 10-year guarantee from day one.
No. It is illegal in the UK to install, repair, or service a gas boiler unless you are on the Gas Safe Register. Unregistered gas work is a criminal offence carrying fines of up to £6,000 or six months in prison. It also invalidates your home insurance and is extremely dangerous. Always use a Gas Safe registered engineer and check their registration number at GasSafeRegister.co.uk before work begins.
How we estimated these ranges
This is a guide only. The ranges below are intended for early budgeting and trade benchmarking. They are not a substitute for a site visit or an itemised quote from a qualified tradesperson. Always get a site-specific quote before agreeing work.
What's included in these ranges: typical labour costs, common materials at standard specification, and routine preparation or installation work for a standard project of this type.
What's excluded: unusual access (multi-storey, restricted parking), unforeseen structural issues, specialist design or architect fees, planning and building control application fees, premium or high-end finishes, emergency or out-of-hours work, and regional extremes.
Regional note: London, the South East and remote rural areas can vary significantly from the UK averages shown. London labour rates in particular can run 30–50% higher than national averages on the same scope.
Sources and checks used:
- Publicly available UK trade supplier pricing (2025–2026)
- Common day-rate and labour-duration assumptions used in trade quoting
- Internal example quote structures from TailoredQuote platform data
Last reviewed: May 2026 by TailoredQuote. Prices in this guide will be reviewed and updated periodically.
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