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.

Last updated: April 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.

Summary Cost Table

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:

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?

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