There’s no single price ratio that decides this. It’s a weighing-up of evidence, and the first piece of evidence is a proper diagnosis of the actual fault. Repair usually makes sense when the fault is a one-off on a reasonably young boiler, the part is a routine one that’s still readily available, and the heating system around it is in decent condition. Replacement moves ahead when several factors stack up together. Breakdowns arriving as a pattern rather than a one-off, a boiler well into its second decade, parts becoming scarce or discontinued, the manufacturer winding down support for the model, poor efficiency, and a tired heating system underneath it. For budgeting context, most UK boiler repairs cost £120–£750, averaging around £300, while a like-for-like combi replacement typically costs £2,500–£4,000 supply and installed. Those are market figures, not a quote. 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 evidence that decides it
No single factor settles this on its own, and a price rule of thumb is a poor substitute for looking at the actual evidence. Weigh these seven together:
The diagnosed fault
A specific, identified, routine fault
Vague, intermittent, or several faults at once
Age
Under about 10 years
Well into its second decade
Repeat history
First fault, or the first in years
Faults arriving yearly, or the same fault returning
Parts availability
Standard part, readily stocked
Scarce, long lead time, or discontinued
Manufacturer support
Model still supported. Guarantee may apply
Model withdrawn from support
Efficiency
Modern condensing boiler
Pre-condensing or poorly performing unit
The wider system
Clean, protected, no recurring symptoms
Recurring pressure loss, leaks or contamination
One or two right-column answers isn’t decisive. Several together usually are. If it’s mixed, read on.
Is it worth repairing a boiler?
Usually, yes, when the fault is a one-off on a boiler under about ten years old and the part is routine and readily available. It tips the other way when breakdowns repeat, parts are scarce, the manufacturer has withdrawn support, or the wider system is tired. The seven-factor table above is the honest version of the answer. Weigh the factors together rather than leaning on a single rule of thumb.
This plays out differently across West London’s housing stock. A lot of our work is in Victorian and Edwardian conversions, where the boiler often sits on a heating system that’s older than the boiler itself, tucked into a boxed-in kitchen cupboard or a loft with a long flue run. A repairable boiler on a tired, unprotected system in one of these conversions is a different call to the same fault on a newer estate install. The system underneath matters as much as the boiler on top of it.
What does a boiler repair cost?
Across the UK, a typical boiler repair costs £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?
Replacing a combi with a new combi in the same location typically costs £2,500–£4,000 supply and installed across the UK in 2026, with the average total for a gas combi about £3,000. Converting from a regular or system boiler averages nearer £4,000. London usually sits toward the upper end, because labour costs more here. 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 guarantee measured in years. That’s valuable, but it’s not a blanket promise that no repair will ever cost you anything. What’s covered depends on the guarantee’s terms and on the cause of the failure. Damage, system contamination, incorrect installation or missed servicing are commonly excluded or can invalidate cover, and the conditions vary by manufacturer, model and installer scheme. Read the exact current terms. 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.
Manufacturer support. Separate from parts on the shelf. Once a manufacturer withdraws technical support for a model, diagnosis gets harder and future repairs get less predictable. Ask the engineer whether your model is still supported.
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 explains why. Modern condensing boilers capture and reuse heat from flue gases that older models lose. The size of the saving depends on your home, your current boiler and your controls, so it’s worth getting it estimated for your property rather than assuming a headline number. A new boiler won’t pay for itself overnight, but on an old non-condensing unit the running-cost gap is real and permanent.
An ageing system underneath the boiler. The older a boiler, the older the heating system around it. Sludge (black magnetite from internal corrosion) is an important cause of circulation and component problems on a tired circuit, where it can restrict the pump, the diverter valve and the heat exchanger. It’s often part of what tips an older boiler over the edge. A new boiler on a cleaned, well-inhibited system with a magnetic filter effectively starts that clock over. If contamination is suspected, the sensible order is testing the system water first, then proportionate cleaning if it’s confirmed.
When repair is clearly the right call
Balance matters. Plenty of boilers get written off prematurely. Repair with confidence when the boiler is still within its guarantee and the fault falls inside the cover (always check the terms before paying for something that may be covered), when it’s a first fault on a younger boiler, or when the diagnosis is a known, routine 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. Worth being accurate about the compliance side, though. The annual gas safety check (CP12) assesses whether an appliance is safe at that visit, and age alone doesn’t determine the outcome. A well-maintained older boiler can pass, and a newer one with a fault may not. Plenty of landlords we work with across West London still choose to replace proactively rather than nurse a tired boiler through another winter. A new install brings a manufacturer’s guarantee, 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 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 about ten years old, the fault is a one-off, and the part is routine and available. Most UK repairs average around £300. It tips toward “no” when several factors stack up: repeat breakdowns, scarce parts, a withdrawn model and a tired system.
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, the manufacturer has withdrawn support, efficiency is poor, or the wider heating system is in poor condition. Any one of these alone isn’t decisive. Several 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. 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 guarantee?
Yes, and it’s measured in years. We register yours as part of the installation. It isn’t a promise that no repair will ever cost you anything, though. What’s covered depends on the guarantee’s terms and the cause of the failure, so check the exact conditions for your model.
How long does a boiler last?
It varies a great deal with the model, how it was installed, how well it’s been serviced and the condition of the system around it. Boilers kept on a clean, well-protected system and serviced to the manufacturer’s schedule tend to last longest. Once a boiler is well into its second decade 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 manufacturer’s guarantee, fewer call-outs and less disruption for the tenant.
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.
- WhatsApp us. Book in 60 seconds
- Call 020 8051 2124. Our line is answered 24/7 and we’ll get your details to an engineer
- See the services: boiler repairs · boiler installation
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 ranges for budgeting only. Condensing-boiler efficiency background is from the Energy Saving Trust. Guarantee conditions vary by manufacturer, model and installer scheme. Check the exact current terms for your own boiler. Your price depends on your home and the fault. We confirm exact prices with a free survey and fixed written quote.
