How Much Does a New Boiler Cost in London? (2026 Prices)

A new boiler in London in 2026 typically lands somewhere between £2,200 and £4,800 fitted, depending on the type, the brand, and how complicated the install is. There is no single right answer, so the honest version is that you need to know what affects the price before you can spot a fair quote.

Below is what we are seeing across South London right now, drawn from real jobs our engineers have priced and installed this year.

Combi, system, or regular: which one are you replacing?

The boiler type drives most of the price. A combi heats water on demand and runs a single unit. A system boiler works with a hot water cylinder. A regular (or heat-only) boiler works with a cylinder and a cold water tank in the loft.

Swapping like for like is always cheaper. Switching from a regular system to a combi means removing the tank and cylinder, rerouting pipework, and often upgrading the gas supply pipe to 22mm. That conversion alone can add £600 to £1,200 on top of the boiler cost.

2026 boiler prices fitted in London

These figures are for a straight swap in a typical 2 or 3 bed property in South London, fully fitted, including a magnetic system filter, a new programmer, and a power flush where needed.

• Combi boiler, budget tier (Ideal Logic Max, Baxi 600): £2,200 to £2,700
• Combi boiler, mid tier (Worcester Bosch 2000, Vaillant ecoTEC pro): £2,700 to £3,400
• Combi boiler, premium (Worcester Bosch 4000/8000, Vaillant ecoTEC plus): £3,400 to £4,200
• System boiler fitted (no cylinder change): £2,600 to £3,800
• Regular boiler fitted (no cylinder or tank change): £2,400 to £3,600
• Conversion from regular to combi: add £700 to £1,400 on top of the combi price

If you live in a flat with a vertical flue or a tight cupboard install, expect another £150 to £400 for the extra time and parts.

What you are actually paying for

Roughly half the bill is the boiler itself. The rest is labour (typically two engineers for a day or two), the flue kit, the magnetic filter, system flushing, the gas tightness test, the Gas Safe notification, and the manufacturer warranty registration.

A power flush, which clears sludge from the system before fitting a new boiler, runs £350 to £550 on its own. Most decent installers include it because skipping it voids the warranty on a lot of modern boilers.

Brands worth knowing

Worcester Bosch tends to be the safe pick. Reliable, easy to get parts for, and most engineers know them inside out. The 4000 and 8000 series come with 10 to 12 year warranties when fitted by an accredited installer.

Vaillant runs Worcester close on quality and the ecoTEC range is genuinely well built. Ideal is the value option, fine for a smaller property or a rental. Baxi sits in the middle, decent kit, slightly cheaper labour to repair.

Avoid no-name brands and ex-display units sold cheap online. The warranty rarely transfers and parts can be a nightmare to source two years later.

Repair or replace?

If your boiler is under 8 years old and the repair is under £400, fix it. If it is 12 years or older and breaking down twice a winter, replacement usually pays for itself in 4 to 6 years through lower gas bills. A new A-rated condensing boiler is around 92% efficient. Anything pre-2005 is probably running at 70% or less.

Other replacement triggers: parts no longer manufactured, persistent leaks from the heat exchanger, repeated PCB failures, or any sign of the casing getting hot.

Boiler Upgrade Scheme

The government Boiler Upgrade Scheme is for heat pumps and biomass boilers, not gas boilers. It pays £7,500 toward an air source heat pump install. If you are interested in switching off gas, that grant is worth knowing about, but it does not apply to a like-for-like gas boiler swap.

How to get an honest quote

Get three quotes. Make sure each one is from a Gas Safe registered engineer (check the card on site, do not just take their word). Ask what magnetic filter they use, whether a power flush is included, and what warranty length the manufacturer offers when they fit it.

If a quote is significantly cheaper than the others, ask what is missing. Usually it is the filter, the flush, or the flue kit being added later as an extra.

For homeowners in Bromley and the surrounding area, our Bromley plumbers and Gas Safe engineers handle the full quote-to-install in around 5 working days for most jobs. Croydon residents can speak to our Croydon plumbing team for the same. You can see the full scope of what we cover on the plumbing services page, or request a written quote and we will price the job properly before any commitment.

A quick note on running costs

A modern A-rated combi running a 3 bed home in South London on the current gas cap costs around £950 to £1,400 a year. An older non-condensing boiler in the same property is closer to £1,300 to £1,800. The annual saving is real, but it is not the £600 some sales pitches claim.

Get the install done properly, get it serviced every year, and a good boiler will give you 12 to 15 years of trouble-free heating.

Sizing matters more than brand

An oversized boiler is the most common install mistake we see. Fitting a 30kW combi in a 2 bed flat with one bathroom is wasteful, runs the boiler in short cycles which shortens its life, and gives no benefit because the radiators cannot move that much heat.

A proper heat loss calculation should be done before quoting. As a rough guide: 24kW combi for a 1 to 2 bed flat or small house, 28 to 30kW for a 3 bed semi, 35kW+ for a 4 bed with two bathrooms or for system boilers feeding a cylinder. If a quote does not mention the kW output, ask why.

What a service should cover

Annual servicing is what keeps the warranty valid and catches problems early. A proper service includes flue gas analysis, checking the gas pressure, cleaning the condensate trap, inspecting the heat exchanger, checking the magnetic filter, and testing the safety interlocks. Cost is £80 to £130 in 2026.

If a 'service' is done in 20 minutes with no flue gas analyser involved, it is a visual check, not a service. Worcester and Vaillant both require a documented service with readings to maintain the long warranty.

What to ask before signing the contract

Five questions that separate good installers from cheap ones: what kW output is being fitted and why, is a power flush included or extra, what magnetic filter brand is going on (Adey MagnaClean and Fernox TF1 are the standards), how long is the warranty when you fit it, and who notifies Building Control. Any installer that fudges those answers is hoping you do not check the small print.

Lastly, get the start date and finish date in writing. A typical combi swap takes one full day, a regular-to-combi conversion takes two. If the quote says three days, ask why.