Boiler Replacement Cost Calculator UK

How the Boiler Replacement Cost Calculator Works

Enter your property size, boiler type you have now, type you want and whether new boiler stays in the same spot. The calculator combines typical unit prices with realistic labour costs to produce a supply and fit estimate.

Current UK benchmarks behind the numbers, a like for like combi swap typically costs £1,800 to £3,500 with most quotes landing around £2,300. A system boiler replacement runs £2,300 to £5,000, a conventional boiler £3,000 to £4,500 and converting from a regular or system boiler to a combi £3,000 to £4,500 because of extra pipework and cylinder removal.

What Drives the Price

Four factors move a boiler quote more than anything else.

The type of job: A combi replacing a combi in same position is a single day’s work. Changing boiler type, relocating the unit or converting a back boiler can stretch to two or three days and add over a thousand pounds in labour alone.

Boiler brand and warranty: Premium brands like Worcester Bosch, Vaillant and Viessmann cost more upfront but often carry 10 to 12 year warranties. Ideal and Baxi offer solid performance at a lower price with shorter cover. A longer warranty is worth real money over the boiler’s life.

Output size: A flat or small terrace suits a 24 to 28kW combi while a 3 bed semi typically needs 28 to 32kW. Bigger homes and multiple bathrooms push towards 35kW or a system boiler. A proper heat loss calculation beats guesswork here because an oversized boiler cycles inefficiently and wastes gas.

Location: Labour rates in London and South East run noticeably above national average, which can add several hundred pounds to an otherwise identical job.

The Extras Quotes Often Leave Out

The gap between two quotes is often in what they include rather than boiler itself. Commonly added items are a powerflush to clear sludge from system at £400 to £900, a magnetic filter to protect new boiler, a smart thermostat, upgraded gas pipework where existing run is undersized and flue changes. A quote that looks cheap may simply have left these out, so always compare the full scope line by line.

Combi, System or Conventional

Around 70 percent of UK replacements are combi boilers, which heat water on demand with no cylinder or loft tank. They suit homes with one bathroom but struggle when two showers run at once. System boilers store hot water in a cylinder and keep pressure strong across multiple bathrooms, at cost of cylinder space and a higher install price. Conventional boilers with a cylinder and loft tank mainly make sense as like for like replacements in older properties where converting would mean extensive pipework changes.

Is It Worth Replacing Rather Than Repairing

Most boilers last 10 to 15 years with annual servicing. Past that point efficiency drops towards 80 to 85 percent against roughly 94 percent for a new A rated condensing model and repairs become more frequent. If your boiler is over 12 years old and repair bills are stacking up, replacement usually wins. If it is younger and this is the first fault, a repair normally makes more sense.

Worth knowing on funding side, £7,500 Boiler Upgrade Scheme grant applies to heat pumps rather than gas boilers, while the ECO4 scheme can fund boiler replacements for eligible low income households. From 2026 the Future Homes Standard stops gas connections in new builds, but replacing a gas boiler in an existing home remains fully permitted.