What sits inside a boiler replacement cost.

A published set of quotes

Heatable’s new boiler cost guide, updated 9 October 2026, uses 2,000 of its own quotes from January to June 2026. In that set, the median for a standard combi replacement was £2,300. Most straightforward combi swaps were quoted between £2,150 and £3,000.

The same page puts a new boiler, installed, in a wider span of about £1,700 to £6,000 and above. The upper end is the awkward job: a conversion, a back boiler coming out, a boiler moving rooms, a flue that has to take a new route, or pipework that has to be renewed.

Heatable also points at earlier government retrofit assumptions of about £1,600 to £4,000 for a replacement gas boiler and about £2,500 to £5,000 for an oil boiler. Those assumptions can leave out controls, a new cylinder and unusual flue work. Use them as a second reference, then read the quote in front of you.

That national page does not publish a pound total for Manchester, Birmingham, Leeds or Bristol.

London has a published average. The other four cities do not.

Heatable’s London boiler page, updated 12 August 2026, puts an overall average new-boiler cost in London at about £3,700. The page describes that as roughly £1,000 over the national average it is using. It puts a London combi installation at an average of £3,061. In the London postcode table on that page, South East London averages £3,900 and North West London averages £3,125.

The same page gives a London average of £4,150 for regular and system boilers, and £4,500 for a conversion. Those are averages for a wider job than the national like-for-like combi band of £1,800–£3,500.

Lower on the page, a regional table is labelled a crude estimation. Manchester is about 2% under the national average, Birmingham about 1% under, Leeds about 1% under, and Bristol in line with it. London is shown there as about 2% over. That 2% is not the same claim as the £3,700 average above. The table does not turn the percentages into pound totals for Manchester, Birmingham, Leeds or Bristol, and this page does not calculate them.

A straightforward combi swap in a London flat can still sit nearer the national band than the £3,700 average. A conversion, a back boiler, or a flue that has to move is what takes a job above £1,800–£3,500, in London and in the other four cities.

What to have written on the quote

Ask for the make, the model and the output, then whether these sit inside the figure: labour, the flue kit, a magnetic filter, the controls, a chemical flush, removal of the old boiler, and VAT. A vertical flue, scaffold, lead or microbore pipework, or a boiler that has to move, is the sort of extra the same guide says should be named before the work starts.

The person who works on the gas appliance has to be Gas Safe registered for that work. Who is allowed to work on gas sets out the HSE rule and the emergency number. A record on this site shows Gas Safe only when the record already has it.

A heat pump grant is a different job from a gas boiler swap. If you are replacing the heating system in England or Wales, read whether the Boiler Upgrade Scheme is still open. The grant is a discount on an installer’s quote. It is not a price this site sets.

Who you phone

Boiler and gas work sits on the plumbing and heating list. Local lists large enough to open as a set are London and Manchester. You phone the business yourself. Get contact details does not send a message for you.

If the gauge keeps falling, or you smell gas, use the pressure note before you treat it as a straight replacement.