Repair the boiler when the fault is a one-off, the boiler is still reasonably young, and the fix is a modest part. Most UK boiler repairs cost £120–£750, averaging around £300 (Checkatrade, May 2026). Replace it when breakdowns are becoming a pattern, the boiler is well into its second decade, parts are getting hard to source, or a single repair bill is approaching half the cost of a new installation. That’s our rule of thumb for when the maths stops working. A new boiler typically costs £1,800–£4,500 fully installed in the UK in 2026, with London toward the upper end. These are market figures for budgeting, not a quote. The honest answer is usually obvious once a Gas Safe engineer has diagnosed the actual fault, which is why we quote the repair and give a straight view on replacement in the same visit. See our boiler repairs and boiler installation services.
Nobody wants to spend £300 fixing a boiler that dies again in November, and nobody wants to spend thousands replacing a boiler that needed a £150 part. Here’s how to tell which side of the line you’re on.
The quick decision table
| Repair makes sense when… | Replacement makes sense when… |
|---|---|
| It’s the first fault, or the first in years | Breakdowns are a pattern, you’re on first-name terms with an engineer |
| The boiler is under ~10 years old | It’s well into its second decade and showing it |
| The fix is a modest, available part | Parts are scarce or discontinued for your model |
| The boiler is still under warranty | One repair bill is nearing half the cost of a new install |
| The system around it is healthy | Pressure loss, leaks or sludge problems keep coming back |
| You’re planning to move soon | Your bills are creeping up on an old, inefficient model |
If you’re ticking mostly left-column boxes, fix it. Mostly right-column, it’s time to talk about a new boiler. Mixed? Read on.
What does a boiler repair actually cost?
Across the UK, Checkatrade’s 2026 repair cost guide (updated May 2026) puts a typical boiler repair at £120–£750 including parts, averaging around £300, with most common faults landing between £100 and £500. Emergency callouts run higher, typically £225–£675. As ever, these are national market figures for budgeting, not a quote.
The number itself matters less than the pattern. A £250 fan replacement on an eight-year-old boiler that’s otherwise been faultless is money well spent. The same £250 on a fifteen-year-old boiler that had a £300 pump last winter and a sensor the year before is something else: you’re buying a new boiler in instalments, and getting an old boiler at the end of it.
What does a new boiler cost?
A new boiler in the UK typically costs £1,800–£4,500 fully installed in 2026, with London usually toward the upper end of the range: a straightforward like-for-like combi swap at the bottom, bigger or more complex jobs at the top. We’ve broken the full picture down in our new boiler cost guide for West London, and if you’re weighing boiler types, start with combi vs system vs heat-only.
Worth folding into the maths: a new boiler comes with a manufacturer’s warranty measured in years, meaning the repair-bill question disappears entirely for the life of the warranty. Modern condensing boilers also waste less of the gas you pay for than the old non-condensing models they replace.
The tipping points that decide it
Age and parts. Once a boiler is well into its second decade, two things happen: components wear out in clusters rather than one at a time, and manufacturers begin discontinuing parts. When an engineer has to hunt for a part for your model, that’s the market telling you something.
Repeat breakdowns. One fault is a fault; three winters of faults is a trajectory. Add up what you’ve spent over the past couple of years; homeowners are often startled by the total.
The half-way rule. Our rule of thumb: when a single repair quote approaches half the cost of a replacement, replacement usually wins. You’d be putting serious money into old technology with no warranty behind it.
Recurring system symptoms. Pressure that keeps dropping after every fix, radiators that sludge up again, leaks that migrate: sometimes the boiler is the victim of a tired system, and sometimes it’s the cause. Either way, patching symptoms annually costs more than solving it once.
Efficiency. If your boiler predates condensing technology, a meaningful slice of every gas bill is going up the flue rather than into your radiators. The Energy Saving Trust estimates that replacing an old G-rated boiler with a new A-rated model and a full set of heating controls saves around £420 a year in Great Britain. A new boiler won’t pay for itself overnight, but on an old unit the running-cost gap is real and permanent.
An ageing, sludged-up system. The older a boiler, the older the heating system around it — and sludge (black magnetite from internal corrosion) is the biggest driver of repeat breakdowns, clogging the pump and diverter valve and blocking the heat exchanger on a tired system. It’s usually what tips an older boiler over the edge. A new boiler on a freshly cleaned, well-inhibited system with a magnetic filter effectively starts that clock over. (Hard water adds a hot-water-side toll on top in areas like ours, but the sludge in an ageing circuit is the bigger factor.)
When repair is clearly the right call
Balance matters. Plenty of boilers get written off prematurely. Repair with confidence when the boiler is under warranty (never pay for what the manufacturer covers), when it’s a first fault on a younger boiler, or when the diagnosis is a known, modest part: fans, sensors, diverter valves and PRVs are routine swaps, not death sentences. We repair boilers across Hammersmith, Shepherd’s Bush and the wider patch every week that will happily run for years yet.
Repair or replace in a rented property?
If it’s a let property, the decision — and the cost — sits with the landlord. The boiler is the landlord’s appliance to keep in working order, so a tenant should report a fault rather than pay for it. The maths is a little different, too. An ageing boiler that keeps breaking down means emergency call-outs, a cold tenant and the risk of a disrepair complaint, and a boiler near the end of its life is also more likely to fail the annual gas safety check (CP12). Plenty of landlords we work with across West London choose to replace proactively rather than nurse a tired boiler through another winter: a new install brings a manufacturer’s warranty, far fewer call-outs, and a tenant who isn’t ringing about the heating. If you let property, we can look at the numbers and the compliance side together.
How to decide in one visit
You don’t have to make this call blind, and you shouldn’t have to make it under sales pressure. Our approach: a Gas Safe engineer (657972) diagnoses the actual fault, gives you a fixed price for the repair, and, if the boiler’s genuinely near the end, a straight view on replacement with a free home survey and fixed written quote. No upselling, no scare tactics; most of the time the numbers make the decision for you.
Frequently asked questions
Is my boiler worth repairing?
Usually yes if it’s under ten years old, the fault is a one-off, and the part is modest and available; most UK repairs average around £300 (Checkatrade, May 2026). It tips toward “no” when breakdowns repeat, parts are scarce, or one bill nears half the cost of a new install.
When should a boiler be replaced?
When the evidence stacks up: it’s well into its second decade, faults are arriving yearly, parts are hard to source, efficiency is poor, or a repair quote approaches half the cost of replacement. Any one of these alone isn’t decisive; two or three together usually are.
How much does a boiler repair cost in 2026?
Typically £120–£750 including parts, with the UK average around £300 and most common faults between £100 and £500, per Checkatrade’s May 2026 guide. Emergency repairs run higher, around £225–£675. These are national market figures for budgeting; a proper diagnosis gets you a fixed price.
Is it cheaper to repair or replace a boiler?
A repair is almost always cheaper today. The question is whether it stays cheaper. One modest fix beats replacement easily. Repeated fixes on an ageing boiler often add up to a significant share of a new install, with no warranty and worse efficiency to show for it.
Does a new boiler come with a warranty?
Yes. Manufacturer warranties on new boilers are measured in years, and we register yours for you as part of the installation. That’s a real part of the repair-or-replace maths: during the warranty period, the repair-bill question largely disappears.
How long does a boiler last?
The Energy Saving Trust puts a typical boiler’s lifespan at 10 to 15 years. Well-serviced boilers on a clean, well-inhibited system can go longer; boilers that miss their annual service, or run on a sludged-up system, tend to sit toward the lower end. Once you’re past that window and facing a fault, replacement is worth weighing seriously.
Who decides whether to repair or replace a boiler in a rented property?
The landlord. The boiler is the landlord’s appliance to keep in repair, so a tenant should report a fault rather than pay for it. Many landlords replace an ageing, repeatedly failing boiler proactively — it means a warranty, fewer call-outs and less risk of failing the annual gas safety check (CP12).
Want a straight answer on yours?
Tell us what the boiler’s doing and we’ll diagnose it, price the repair, and give you an honest view on whether it’s worth it.
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We’re Gas Safe registered (657972) and cover West and North West London. Heating that just works, no drama.
About the author Adam Said is a Gas Safe registered domestic gas engineer (657972) at The Happy Heating Co, repairing and replacing boilers in homes across West and North West London. This guide reflects what we see on real jobs every week.
Related reading
- How much does a new boiler cost in West London?
- Combi vs system vs heat-only boiler
- Boiler repairs in West London
- Boiler installation
- Why is my boiler losing pressure?
Cost figures are typical UK market averages from Checkatrade’s boiler repair (May 2026) and new boiler cost guides, for budgeting only; efficiency and lifespan figures are from the Energy Saving Trust. Your price depends on your home and the fault — we confirm exact prices with a free survey and fixed written quote.
