By 
£60 to £90 / hr
Gas Safe repair labour rate
£1,800+
Like-for-like combi swap (fitted)
~£300 / yr
Gas savings from G → A boiler
12 years
Age at which most boilers tip to "replace"
Indicative UK figures, May 2026. Replacement cost ranges include parts, labour and standard waste removal.
When a UK boiler dies on a January morning, the standard advice, "get a quote, then decide", is too narrow. The quote is one number. The right number is the five-year total cost of running this boiler against the five-year total cost of a new one. They are rarely close.
A 12-year-old combi that has just dropped its PCB will probably swallow another £300 to £500 of repairs over the next two years even if you fix today's fault. Meanwhile a modern condensing boiler in the same home is using 25 to 30% less gas, which on a typical UK heating bill is £200 to £400 a year. Stretch that over five years and the maths is almost always one direction.
The widget below does this calculation for your boiler. The rest of the guide explains where the figures come from, which faults usually flip the decision, and how to check if you qualify for a free replacement through the Energy Company Obligation.
Should you repair the boiler or replace it?
Plug in the boiler's age, today's quote and your gas spend. We compute the 5-year cost of each path and tell you which one wins.
Pre-2005 boilers are usually D or below. Post-2010 A-rated is the modern norm.
5-year total cost comparison
- Keep + repair £
- Replace today £
- Net 5-year saving £
Assumes future repair pattern from boiler age + efficiency uplift from a modern A-rated replacement. ECO grant not included.
Calculations verified May 2026. Source: UK Gas Safe engineer parts pricing + average condensing boiler efficiency data.
Where standard advice fails
Why most repair-or-replace articles miss the point
The classic UK advice is the "50% rule": if a single repair costs more than half the price of a new boiler, replace. It is a reasonable rule of thumb. It is also incomplete, because it ignores efficiency.
An old D-rated boiler running at 80% efficiency wastes roughly £200 to £400 a year of gas compared with an A-rated condensing replacement. Over five years that is £1,000 to £2,000 of pure waste. So even a "cheap" repair on an old, inefficient boiler can be the wrong call, because you are committing to another four or five years of overpaying for gas.
The other thing standard guides understate is the future repair pattern. A 12-year-old boiler will probably need another repair in the next 18 months. A 5-year-old boiler probably will not. The right comparison is not "this repair vs a new boiler". It is "this repair plus the expected next two repairs vs a new boiler that pays you back in gas savings".
And finally, the Energy Company Obligation is barely mentioned. For UK households on a qualifying benefit (Universal Credit, Pension Credit, Income Support and others), an inefficient old boiler can be replaced free of charge. Repairing it is almost never the right move. Always check ECO eligibility before paying for a major repair on an old boiler.
The decision rules
When the decision is obvious, in both directions
For most UK households, the right answer falls into one of these two lists before you even reach for the calculator.
Repair, almost always
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Low water pressure
Top-up loop or pressure relief valve. Usually a £90 to £140 fix if it is the valve, £0 if it is just a top-up.
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Cold radiators
Air or sludge in the system. Bleed (free) or power flush (£350 to £700). Not a boiler fault.
-
Single cheap part failure
Thermostat, air vent, ignition. Fitted price £80 to £160. Almost always cheaper than replacement.
-
Boiler under 10 years old
Modern condensing boilers are designed for 12 to 15+ years. A first repair is rarely a sign of approaching end of life.
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Boiler still under warranty
Most major brands give 7 to 12 years if you keep up the annual service. The repair is free, call the brand first.
Replace, almost always
-
Boiler 12+ years old + £400+ repair
Parts are getting scarce, efficiency has dropped from ~94% to ~80%, and an A-rated replacement saves £200 to £400 a year on gas.
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Cracked heat exchanger
The single most expensive part to replace. Fitted price often £600 to £900. On most boilers, replacement is cheaper.
-
Failed PCB on an obsolete model
Once the manufacturer discontinues the printed circuit board, every future fault becomes "replace the boiler". The first PCB failure is often the moment.
-
Heavy corrosion or repeated leaks
Cast-iron leaks, rust on the external casing or a corroding heat exchanger are end-of-life signs.
-
Eligible for ECO grant
If you receive a qualifying benefit and the existing boiler is inefficient, the Energy Company Obligation may fund a full replacement. Repair is rarely worth it in that case.
Typical UK part costs
What each repair actually costs in 2026
Fitted prices including labour. Use them to sanity-check any quote you are given. A part priced double the figure here means you should ask for a written breakdown.
| Part | Fitted price (UK 2026) | Default recommendation |
|---|---|---|
| Boiler fan | £200 to £280 | Repair |
| Printed circuit board (PCB) | £250 to £380 | Repair if model still supported |
| Heat exchanger | £500 to £900 | Often replace the boiler |
| Diverter valve | £170 to £240 | Repair |
| Water pump | £190 to £260 | Repair |
| Gas valve | £200 to £280 | Repair |
| Pressure relief valve | £90 to £140 | Repair |
| Thermostat | £90 to £160 | Repair |
| Auto air vent | £70 to £120 | Repair |
If you replace
UK boiler replacement costs by type, May 2026
"Fitted" prices include installation, removal of the old unit, basic flue work and waste disposal. Add £400 to £900 for moving the boiler to a new location or changing boiler type.
| Boiler type | Tier | Unit only | Typical fitted price |
|---|---|---|---|
| Combi boiler | Budget (Ideal / Baxi entry) | £900 to £1,300 | £1,800 to £2,500 |
| Combi boiler | Mid-range (Worcester / Vaillant) | £1,300 to £1,800 | £2,300 to £3,200 |
| Combi boiler | Premium (Viessmann / top-spec Worcester) | £1,800 to £2,400 | £3,000 to £4,000 |
| System boiler | Mid-range | £1,200 to £1,700 | £2,200 to £3,200 |
| Conventional / regular | Mid-range | £1,000 to £1,500 | £2,000 to £3,000 |
| Heat pump (swap from gas) | Air source | £6,000 to £10,000 | £8,000 to £14,000 (BUS grant £7,500) |
Heat pump figures shown net of the Boiler Upgrade Scheme (BUS) grant value at the time of writing. Always check current grant levels on GOV.UK before quoting yourself.
Insider insight
The free-boiler scheme most UK households never check
The Energy Company Obligation is a government scheme funded by UK energy suppliers. It can pay for a boiler replacement, sometimes in full, for households on qualifying benefits with an inefficient existing boiler. Most eligible households do not realise they qualify.
The qualifying benefits typically include Universal Credit, Pension Guarantee Credit, Income Support, Income-based Jobseeker's Allowance, Income-related ESA, Child Benefit and Housing Benefit. The exact list and obligation period can change, check the live scheme details on GOV.UK before applying. Applications usually go through your energy supplier.
The pricing logic is unusual: the supplier pays the installer, not you. So the lever is not finding a cheap quote, it is finding an installer who accepts ECO funding. Selectra can point you at participating installers.
Check before you pay
If your boiler is over 12 years old and someone in the household receives a qualifying benefit, run an ECO eligibility check before agreeing to any repair quote.
Where to apply
Start at gov.uk/energy-company-obligation or our UK ECO guide.
Make the call the right way
How to actually make the repair-or-replace decision
-
1
Get the diagnosis in writing.
A Gas Safe engineer should tell you which specific part has failed, the replacement cost, and the labour estimate. "It is the boiler" is not a diagnosis.
-
2
Check the warranty status first.
Most major UK brands give 7 to 12 years of cover if the annual service is up to date. A free repair is always cheaper than a paid one. Call the brand before agreeing to anything.
-
3
Run the calculator above with honest numbers.
Use the actual repair quote, your real annual gas spend, and the boiler's real efficiency rating (find it on the boiler badge or the original Energy Performance Certificate).
-
4
Check ECO eligibility before committing.
If anyone in the household receives a qualifying benefit, an inefficient boiler may be replaced free. The repair quote becomes irrelevant in that case.
-
5
Get at least three quotes for replacement.
Use Gas Safe registered engineers, ideally MCS-certified if you are considering a heat pump. Insist on a fixed price, not "from £X". UK quotes vary by £600 to £1,200 for the same job.
-
6
Pair the replacement with a smart thermostat.
A modern condensing boiler with a modulating control (TRVs + smart room thermostat) saves a further 5 to 10% on gas. Without those, you give back part of the efficiency uplift.
Repair-or-replace FAQ
Your repair-or-replace questions, answered
The rule of thumb is the "50% rule": if a repair quote is more than 50% of the cost of a new boiler installed, and the unit is over 10 years old, replace. Add the savings from a higher-efficiency new boiler (typically £200 to £400 a year on gas) and the payback usually lands inside 5 years.
Possibly. The Energy Company Obligation (ECO) scheme funds boiler replacements for households on qualifying benefits (Universal Credit, Pension Credit, Income Support and others) when the existing boiler is inefficient. The scheme is delivered by your energy supplier. Always check the current scheme status on GOV.UK before applying, terms and obligation periods change.
A like-for-like combi swap typically runs £1,800 to £3,200 fitted. Switching boiler type (e.g. conventional to combi, or removing a hot-water cylinder) adds £500 to £1,200 for the pipework and disposal. Heat pump installs start at £8,000 to £14,000 before the Boiler Upgrade Scheme grant.
Sometimes. Air source heat pumps work well in well-insulated UK homes with low-temperature radiators (or underfloor heating). They struggle in old, draughty properties without upgrades. The Boiler Upgrade Scheme grant of £7,500 makes the headline price closer to a premium combi install, but installer choice matters more than the headline cost. Get at least three MCS-certified quotes.
Replacing a G-rated boiler (~60% efficient) with an A-rated condensing boiler (~94% efficient) typically saves £200 to £400 a year on gas for an average UK home, more for a four-bed property with high demand. A new boiler with proper modulating controls (TRVs + smart thermostat) adds a further £80 to £150 a year.
The annual Gas Safe service. At £70 to £95, it catches the slow drifts (combustion, pressure, seal condition) that turn into £400 emergency repairs in January. Missing it also voids the manufacturer warranty. See the boiler service guide.