Boiler Replacement Cost Calculator

As a guide, a like-for-like combi replacement is usually £2,500 to £4,000 supplied and fitted, and a new system or regular boiler around £3,000. Switching from a system or regular boiler to a combi is around £4,000 (Checkatrade, March 2026). Extras such as a new hot water cylinder or a power flush add to the price, and gas boilers are charged at the standard rate of VAT.

Not usually. There is no general free boiler scheme. ECO4 can fund a heating upgrade or replace a broken boiler for some households on certain benefits or lower incomes, where strict rules are met, and it ends on 31 December 2026. It may be fully or partly funded and you may be asked to contribute. In Wales, Warm Homes Nest can include a boiler repair or replacement for eligible households. Check the official scheme before relying on funding.

On Checkatrade's March 2026 figures there is little between them: a like-for-like combi swap is usually £2,500 to £4,000, and a new system or regular boiler around £3,000. Changing type costs more, for example around £4,000 to switch a system or regular boiler to a combi. Choose the type that suits your hot water needs, not just the lowest price.

A straight swap in the same place is often done in a day or two. Moving the boiler or changing its type takes longer. The installer will confirm after a survey, and you may be without heating and hot water while the work is done.

It depends on its condition, efficiency and repair costs. An old non-condensing boiler uses more gas than a modern condensing one, so replacing it usually cuts running costs, while replacing a newer boiler that still works well may save little. Ask an engineer whether a repair would be cheaper before deciding.

A written quote should say whether it covers removing the old boiler, fitting the new boiler and flue, connecting pipework and gas, cleaning and treating the system, commissioning and paperwork. Check whether it includes a power flush (Which? puts these at £300 to £750), a new hot water cylinder, moving the boiler or new controls, and what the warranty requires, such as annual servicing.