Boiler Repair Cost Calculator
Pick the symptom and this prices the likely repair, then tells you honestly whether a boiler of that age is worth fixing at all.
Open the calculator →Price your boiler fault in 30 seconds
4 steps. Covers diagnosis, the part and labour, boiler age and region — with a repair-or-replace steer at the end.
How this calculator works
The calculator prices by symptom, because that is all you can know before an engineer looks. Note the fault code on the display first if there is one — it usually identifies the component and can turn a diagnostic visit into a parts-in-hand repair. Most modern combis flash a code rather than cut out silently — F.28 or F.29 on a Vaillant, or an EA lockout on a Worcester, both point at ignition rather than anything structural, so noting it before you phone can turn a diagnostic call-out into a parts-in-hand fix. And if the boiler is under five years old, check the paperwork before you pay for anything: a five to ten year manufacturer warranty is standard on the mainstream brands now, and a fault inside that window is the maker’s problem, not yours.
Age does not change what a repair costs, but it changes whether you should do it. Past ten years, a repair over roughly £500 is money spent on an appliance near the end of its life, with worse efficiency and thinning parts availability. The calculator flags that rather than quietly encouraging the repair. A useful sanity check on any repair quote for an older boiler: ask the engineer what the same fault would cost to fix again in a year, because on a boiler shedding parts one repair often leads to the next, and that pattern is usually the real signal it is time to replace. When you reach that point it pays to read up on which makes hold up best before committing — our guide to the best boiler brands in the UK weighs reliability and parts backing, and the boiler replacement cost guide sets out what a like-for-like swap runs to in 2026 so you can hold it against the repair figures in the table above.
On gas safety: only a Gas Safe registered engineer may legally work on your boiler. We do not check that for you — ask to see the ID card and verify the licence number on the Gas Safe Register itself, and check the back of the card lists the appliance type being worked on.
Boiler repair costs by fault (2026)
| Fault | Typical 2026 cost | Notes |
|---|---|---|
| Diagnostic call-out | £60–£120 | Often credited against the repair |
| Thermostat or pressure fault | £150–£250 | Sensor or expansion vessel |
| Pump or diverter valve | £250–£450 | The classic combi failure |
| Fan or gas valve | £300–£500 | Noise, or lockout on ignition |
| PCB (circuit board) | £400–£600 | Common write-off point on older units |
| Heat exchanger | £500–£800+ | Usually the moment to price a replacement |
| Out-of-hours call-out | +£80–£150 | Evenings, weekends, bank holidays |
Figures match our boiler repair cost guide. Gas work is legally restricted to Gas Safe registered engineers — check the register yourself before anyone starts.
Boiler repair calculator FAQs
The common rule is past ten years and over about £500 of repair. At that point you are spending on an appliance with limited life left, worse efficiency than a current model, and parts that are getting harder to source. A replacement also restarts a warranty of 5–12 years.
Usually it is credited against the work if you go ahead on the same visit. Confirm that when you book — it is standard, but not universal, and it is easier to agree up front than to argue afterwards. It is also worth asking whether the fee still applies if the boiler turns out to be beyond economic repair, since a fair firm will usually put a diagnostic toward a replacement quote rather than charging you twice to reach the same conclusion.
Ask for the ID card, then type the licence number into the Gas Safe Register yourself rather than relying on the card. Cards expire and can be borrowed. Check the back too: it lists which appliance types that engineer is qualified for.
Not usually. It is often a leaking radiator valve, a failed expansion vessel or a passing pressure relief valve, typically £150–£250 fixed. It is worth acting on quickly, because repeatedly topping up introduces fresh oxygenated water and accelerates corrosion through the system. If the same fault comes back after a repair, ask the engineer to check the expansion vessel pressure specifically, as a vessel that has lost its charge is the most commonly missed cause and cheap to recharge or replace before it drags in bigger bills.
Related cost guides
- Boiler repair cost guide — every fault priced in detail
- Boiler replacement calculator — when replacing beats repairing
- Boiler service calculator — what an annual service costs
- Central heating repairs — faults beyond the boiler itself
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