How Much Does a Boiler Repair Cost in London? 2026 Prices by Fault

Last updated: September 2026

The first cold week of autumn is when most London boilers give up. The heating goes back on after a summer of doing nothing, and a fault that was quietly developing turns into no heating, no hot water, or a boiler flashing an error code. The good news is that most boiler repairs are not a new boiler. This guide sets out what a repair should cost in London in 2026, fault by fault, what a fair quote looks like, which checks you can safely do yourself first, and when it makes more sense to replace rather than repair.

TL;DR

A London boiler repair typically costs £90 to £150 for diagnosis, £100 to £300 for a minor fix, £200 to £500 for a pump or diverter valve, and £400 to £850 or more for a circuit board or heat exchanger. Any work inside the boiler needs a Gas Safe registered engineer.

What a boiler repair costs in London in 2026

No official body publishes boiler repair prices, so the figures below are market-observed ranges, triangulated from dated 2026 price surveys [19][20][21] and adjusted towards the top of each band for London. They include parts and labour. Always confirm whether a quote includes VAT.

Repair tier	Typical London price (2026)	What it usually covers
Diagnosis visit or call-out	£90 to £150	Travel, finding the fault, often the first hour
Minor fix	£100 to £300	Resetting after a lockout, a sensor or thermostat, a small leak from a worn seal
Mid-cost part	£200 to £500	Circulating pump, diverter valve, fan, expansion vessel
Major part	£400 to £850 or more	Printed circuit board (PCB), heat exchanger
Replacement boiler (for comparison)	Several thousand pounds	See our new boiler cost guide

Across the 2026 surveys we reviewed, the range that recurs most often for a complete repair bill is roughly £100 to £500 [20][21]. Which? found that when a repair was needed after an annual service, the average one-off repair cost was £156 [2]. That is the most useful single benchmark for a routine fault, but it is an average of follow-up repairs, not of every breakdown.

Two of the most common problems can cost nothing at all if you catch them early: low pressure that simply needs topping up, and a frozen condensate pipe in a cold snap. Both are covered in the section on what you can safely check yourself.

Fair quote checklist: what a boiler repair quote should include

A fair repair quote, written or sent by message before the work starts, should state:

• The call-out or diagnosis fee, and whether it is deducted from the repair if you go ahead. Many engineers deduct it, but it is trade practice, not a legal right, so get it confirmed in writing.
• Labour, as a fixed price or an hourly rate with an estimate of time.
• Each part by name and price, for example "diverter valve, manufacturer part" rather than "parts".
• Whether parts are genuine manufacturer parts, which matters if the boiler is still under warranty.
• VAT, stated clearly. A sole trader below the VAT threshold may not charge it at all.
• A guarantee on parts and labour, and how long it lasts.
• The engineer's Gas Safe registration number, which you can check before they arrive.
• What happens if the first part does not fix it, because a misdiagnosed fault can mean paying for two parts.

A quote that says only "boiler repair, £450" does not let you compare it with anyone else's.

Boiler repair costs by fault and part

These are the parts and faults that account for most repair bills. Ranges are fitted prices (part plus labour) from dated 2026 market surveys unless noted; London jobs tend to sit at the upper end.

Fault or part	Typical 2026 cost	Notes
Boiler losing pressure (simple top-up)	£0 if you do it yourself	A few minutes with the filling loop
Pressure that keeps dropping	Priced on diagnosis	Usually a leak or a failing component that needs tracing
Frozen condensate pipe	£0 if you thaw it yourself	Otherwise the cost of one call-out
Leak from a worn seal or washer	£100 to £200 [21]	Which? names corroded washers as a common cause of leaks [1]
Circulating pump	£100 to £300 [20][21]	No heating, or noisy, slow-to-heat radiators
Diverter valve	£150 to £350 [20][21]	Hot water but no heating, or the reverse; sources vary widely
Fan	£100 to £200 [21]	Single source, treat as indicative
Expansion vessel or pressure relief valve	Ask for an itemised quote	No reliable dated figure published; falls in the mid-cost band
Printed circuit board (PCB)	£150 to £500 or more [21]	The boiler's control board; model-dependent
Gas valve	£70 to £240 for the part [20]	Labour on top; gas work, so registered engineers only
Heat exchanger	£300 to £650 [20][21]	Often the point at which replacement becomes the better option

The survey sources disagree most on the diverter valve: one quotes £25 to £200 and another £200 to £350 [20][21]. The gap most likely reflects one quoting the part alone and the other the fitted price, which is why a quote that separates parts from labour is worth insisting on.

Which? identifies the three problems its engineers see most often as a boiler losing pressure, a frozen condensate pipe and water leaking from the boiler [1]. The first two are frequently fixable without paying for a part.

Call-out and diagnosis fees

Before any part is fitted, you pay for someone to find the fault. A 2026 survey of gas engineers put the average standard call-out fee at £86 (commonly £65 to £105) and the average emergency call-out at £109 (commonly £90 to £165) across the UK [19]. The same survey puts the average gas engineer hourly rate at £58, with a typical range of £40 to £80, and notes that London sits at the higher end [19].

In London, expect a standard weekday diagnosis visit to cost roughly £90 to £150, which is in line with our emergency plumber cost guide for weekday daytime call-outs. Evenings, weekends and bank holidays cost more; that guide covers out-of-hours rates in detail.

Some engineers quote a fixed diagnostic fee and then a fixed price for the repair. Others charge by the hour from arrival. Either is fine, as long as you know which before they start.

What you can safely check yourself, and what is gas work

A handful of checks are safe for any homeowner and fix a surprising share of "broken" boilers.

1. Check the controls. Is the timer or programmer calling for heating, is the room thermostat turned up, and has the power to the boiler been switched off at the fused spur?
2. Check the pressure gauge. Vaillant advises topping up through the filling loop until the gauge reads between 1 and 1.5 bar for most of its boilers, and Which? describes the target as usually around one bar [17][1]. Check your own boiler's manual first, and note that Vaillant itself recommends having an expert do it if you are not confident [17].
3. Reset once. If the boiler has locked out, the manual will show how to reset it. Resetting repeatedly without fixing the cause is not a fix.
4. Thaw a frozen condensate pipe. In freezing weather a condensing boiler can shut itself down because its condensate pipe has frozen [1]. Baxi advises thawing the exposed outside section with a hot water bottle, a microwaveable heat pack or a cloth soaked in hot water, and warns: "Do NOT use boiling water" [18]. Our guide to frozen and burst pipes covers the wider winter picture.

If the pressure keeps dropping within days of topping up, that is a leak or a failing component, and it needs an engineer. Topping it up again will not fix it.

Everything beyond those checks is gas work. By law, "No person shall carry out any work in relation to a gas fitting or gas storage vessel unless he is competent to do so" [4], which in practice means a Gas Safe registered engineer. Opening the boiler casing, replacing any internal part, or touching the gas supply or flue is on the professional side of that line.

Safety first. If you smell gas or suspect carbon monoxide, call the National Gas Emergency Service on 0800 111 999, turn off the gas at the meter if you can do so safely, and open doors and windows [6]. The Health and Safety Executive lists warning signs of a faulty appliance as yellow or orange rather than blue flames, soot or staining around the appliance, and a pilot light that frequently blows out; symptoms of exposure include headaches, dizziness, nausea and breathlessness [6].

Repair or replace? The age and cost test

A useful rule of thumb: if a boiler is over ten years old and the repair would cost more than about half the price of a new one, replacement is usually the better long-term decision. A younger boiler with a minor, well-understood fault and a good service history is usually worth repairing. It is the same test we set out in our new boiler cost guide.

Three things push the decision towards replacement:

• A major part on an older boiler. A heat exchanger or circuit board on a boiler well past ten years can cost a large fraction of a new installation, and other parts are likely to follow.
• Repeat breakdowns. Several repair visits in one or two winters usually add up to more than they appear to individually.
• Parts availability. Parts for long-discontinued models can become harder to source or take longer to arrive. Ask the engineer whether the part is in stock and how long it will take before you agree to the repair.

If your boiler has failed completely and you have no heating today, the practical route is usually to get it diagnosed first and make the repair-or-replace decision once you know the fault and the price.

Who pays: warranties, boiler cover and renters

Manufacturer warranty. If the boiler is still under warranty, the repair may cost you nothing, but warranties carry conditions. Which? lists three common ways homeowners invalidate them: not using a Gas Safe engineer to install the boiler, failing to register the warranty with the manufacturer within 30 days, and skipping the annual service [3]. Check your paperwork before paying for a repair yourself.

Boiler cover. Which? puts the average boiler cover package at £183 a year, with some plans reaching £300, and judges that boilers rarely need frequent enough repairs for these policies to be cost effective [2]. If you already have cover, call your provider before booking anyone else.

If you rent. A broken boiler is your landlord's problem to fix. The Landlord and Tenant Act 1985 requires a landlord "to keep in repair and proper working order the installations in the dwelling-house for space heating and heating water" [7]. Citizens Advice's guidance is to tell your landlord the boiler is not working, because they are responsible for repairing or replacing it [8]. Report it promptly and in writing, and keep a copy. Awaab's Law, which sets fixed timescales for urgent repairs, currently applies to social housing; private renters rely on the landlord's existing repair duty.

Help with the cost. Citizens Advice notes that low-income households may be able to get help repairing or replacing a boiler, including through the Energy Company Obligation and some local council grants [8]. Ofgem's guidance is that ECO4 runs until 31 December 2026 and can cover a boiler that has broken down and cannot be economically repaired, for eligible households only [12]. The Boiler Upgrade Scheme funds low-carbon heating such as heat pumps, not gas boiler repairs [13]. Contact your energy supplier or Citizens Advice to check what you qualify for.

Your rights when you pay for a repair

The Consumer Rights Act 2015 gives you three useful protections when you pay an engineer:

• The work must be done "with reasonable care and skill" [9].
• If no price was agreed in advance, you must pay "a reasonable price for the service, and no more" [10].
• If no time was agreed, the work must be done "within a reasonable time" [11].

This is another reason to agree the price before the engineer starts. A written quote removes the argument about what "reasonable" means.

How to check your engineer is Gas Safe registered

Before anyone works on your boiler, check their registration. The Health and Safety Executive explains that you can search the Gas Safe Register online by postcode, call the free helpline on 0800 408 5500, or text Gas followed by the engineer's seven-digit licence number to 85080 for a confirmation reply [5]. When they arrive, ask to see their Gas Safe ID card, which shows the types of gas work they are qualified to do [5]. Make sure it covers domestic gas boilers.

If you rent and your landlord arranges the repair, the same checks apply. Our guide to the landlord gas safety certificate covers the annual check landlords must arrange.

Why boiler repairs cost more in London

London repair prices sit at the top of national ranges for practical reasons, not a postcode mark-up.

• Vehicle charges. A van entering central London pays the £18 daily congestion charge [15], and a non-compliant van pays £12.50 a day for the Ultra Low Emission Zone (ULEZ) [16]. Many firms build these into their call-out fee.
• Parking. Paid parking in central and inner boroughs adds to the cost of every visit.
• Access. Boilers in period terraces, mansion blocks and converted flats are often in cupboards, lofts or kitchens with awkward access and older pipework.
• Travel time. Fewer jobs fit into a day across London traffic, which pushes day rates up.
• VAT. Larger firms are VAT-registered and must add 20 percent; a sole trader with turnover below £90,000 does not have to register [14]. Two quotes that look far apart may be the same price before VAT.

How to avoid the next repair bill

The single best defence is an annual service. It catches worn seals, failing sensors and low inhibitor levels before they become breakdowns, and it keeps a manufacturer warranty valid [3]. Our boiler service cost guide explains what a service should include and what it costs in London.

If your radiators are cold in patches rather than the whole system failing, the cause is often the radiators, not the boiler. Our guide to radiators that will not heat up explains how to read the cold pattern before you pay for a boiler call-out.

Frequently asked questions

How much does a boiler repair cost in London?

Most London boiler repairs cost between £100 and £500 in 2026, including the call-out. A minor fix such as a reset or a sensor typically costs £100 to £300, a pump or diverter valve £200 to £500, and a circuit board or heat exchanger £400 to £850 or more. Always ask for a written, itemised quote before work starts.

Is the call-out fee included in the boiler repair price?

Often, but not always. Many engineers deduct the call-out or diagnosis fee from the final bill if you go ahead with the repair, but this is trade practice rather than a legal right. Ask before the visit whether the fee is deducted, and get the answer in writing so there is no dispute when the invoice arrives.

Can I fix low boiler pressure myself?

Usually, yes. Topping up the pressure through the external filling loop is a routine homeowner task: open the valves slowly until the gauge reads about 1 to 1.5 bar, then close them. Check your manual first. If the pressure keeps dropping within days, there is likely a leak, and you need a Gas Safe registered engineer to trace it.

Is it worth repairing a 15-year-old boiler?

It depends on the fault. A cheap, well-understood repair on an otherwise reliable boiler can be worth doing. But if a boiler is over ten years old and the repair costs more than about half the price of a new one, replacement is usually the better decision, particularly for a heat exchanger or circuit board, or after repeated breakdowns.

Who pays for a broken boiler if I rent?

Your landlord. The Landlord and Tenant Act 1985 requires landlords to keep heating and hot water installations in repair and proper working order, and Citizens Advice confirms the landlord is responsible for repairing or replacing a broken boiler. Report the fault to your landlord or letting agent promptly and in writing, and keep a copy of the message.

Do I need a Gas Safe engineer to repair a boiler?

Yes, for anything beyond basic checks. Topping up the pressure, resetting the boiler and thawing a frozen condensate pipe are safe homeowner tasks. Anything that involves opening the boiler, replacing a part or touching the gas supply or flue is gas work, and by law it must be done by a competent, Gas Safe registered engineer.

Find a Gas Safe engineer near you

Whether your boiler needs a quick diagnosis, a new pump or an honest opinion on repair versus replacement, Loacally connects you with local tradespeople across London, each reviewed by hand before their profile goes live. Find a trusted local heating engineer near you and get your heating working again before the cold sets in.

Sources

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2. Which?. "Getting the best boiler service." Dated 17 September 2025. https://www.which.co.uk/reviews/boilers/article/boiler-maintenance/getting-the-best-boiler-service-a9h945b2brSV (accessed September 2026)
3. Which?. "Common mistakes that can invalidate your boiler warranty." Dated 22 October 2025. https://www.which.co.uk/news/article/common-mistakes-that-can-invalidate-your-boiler-warranty-ah99p4M3O3VL (accessed September 2026)
4. Legislation.gov.uk. "The Gas Safety (Installation and Use) Regulations 1998, Regulation 3." https://www.legislation.gov.uk/uksi/1998/2451/regulation/3 (accessed September 2026)
5. Health and Safety Executive. "Check an engineer - are they Gas Safe registered?" Dated 23 September 2024. https://www.hse.gov.uk/gas/gas-safe-register-check.htm (accessed September 2026)
6. Health and Safety Executive. "Gas safety - Carbon monoxide awareness frequently asked questions." Dated 10 February 2026. https://www.hse.gov.uk/gas/domestic/co.htm (accessed September 2026)
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13. Ofgem. "Boiler Upgrade Scheme guidance for property owners." Updated 2 July 2026. https://www.ofgem.gov.uk/guidance/boiler-upgrade-scheme-guidance-property-owners (accessed September 2026)
14. Gov.uk. "VAT registration thresholds." https://www.gov.uk/vat-registration-thresholds (accessed September 2026)
15. Transport for London. "Congestion Charge." https://tfl.gov.uk/modes/driving/congestion-charge (accessed September 2026)
16. Transport for London. "Ultra Low Emission Zone." https://tfl.gov.uk/modes/driving/ultra-low-emission-zone (accessed September 2026)
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