A broken boiler in winter feels like an emergency - and the price tag varies wildly depending on the fault. Here is what each common repair typically costs, when a new boiler is the smarter spend, and how to keep the bill down.
A diagnostic call-out is usually £70-£120. Small part swaps land around £100-£250; a circuit board or pump is the dearer end. A full replacement starts near £1,800.
Typical UK Prices
| Job | Typical price |
|---|---|
| Diagnostic call-out | £70-£120 |
| Replace a faulty thermostat | £100-£250 |
| Fix low pressure / minor leak | £100-£300 |
| Replace a circulation pump | £200-£400 |
| Replace a circuit board (PCB) | £300-£550 |
| Replace a heat exchanger | £350-£600 |
| New combi boiler (supplied & fitted) | £1,800-£3,500 |
What the Common Faults Cost - and Why
- No heating, hot water fine
- Often a diverter valve or motor - a mid-range part, usually £150-£350 fitted.
- Losing pressure
- Could be a leak or a failed expansion vessel. Cheap if it's a top-up, dearer if it's a part.
- Boiler keeps locking out
- Frequently the PCB or a sensor - the PCB is one of the priciest single repairs.
Repair or Replace?
- Boiler under 8 years old with a one-off fault - almost always worth repairing
- Over 12 years old and breaking down repeatedly - replacement usually wins on running cost
- If a single repair tops half the price of a new boiler, get a replacement quote too
- No longer able to get parts? That decides it for you
Before the Engineer Arrives
Most modern boilers show a code on the display. Read it out when you book - it speeds up diagnosis.
If it reads below 1 bar, low pressure may be the whole problem and a quick fix.
No heating but hot water working (or vice versa) points to a specific part, not the whole unit.
How to Cut the Cost of Repairs
- Service your boiler yearly - it catches small faults before they become big ones
- Keep the warranty paperwork; many repairs are covered for the first few years
- Bleed your radiators each autumn to avoid pump strain
- Don't ignore early warning signs like banging, weak flow, or rising pressure
Try These Checks Before You Pay for a Call-Out
A surprising share of "broken boiler" call-outs turn out to be something the homeowner could have fixed in minutes. Before you book, it's worth ruling out the easy stuff.
- Low pressure - top it up to 1.5 bar with the filling loop
- A frozen condensate pipe in cold weather - thaw it gently with warm water
- A knocked thermostat or timer - our boiler not working checklist runs through all six checks
- One cold radiator isn't a boiler fault - see why a radiator won't heat up
Is a Service Plan Worth It?
Annual cover and service plans spread the cost and usually include a yearly check, but they're not always the cheapest route - especially on a newer boiler still under warranty.
- New boiler under warranty
- Most repairs are already covered for the first 5-10 years, so a separate plan often duplicates it.
- Older, out-of-warranty boiler
- A plan can make sense if breakdowns are getting frequent - but compare it against the cost of replacement.
- Pay-as-you-go
- For a reliable boiler, simply paying for the rare repair is often cheaper over time than monthly cover.
What Drives the Final Bill
Two boilers with the same fault can cost very different amounts to fix. The part itself, how buried it is in the unit, the time of day you call, and whether parts are still made for an older model all feed into the price.
When a New Boiler Wins
If your boiler is over twelve years old and breaking down most winters, the repair bills add up fast - and an older, less efficient unit quietly costs you on every gas bill. Once a single repair approaches half the price of a replacement, it's worth getting a new-boiler quote alongside the repair so you can weigh the two properly.
All gas work must be carried out by a Gas Safe registered engineer. Prices are typical 2026 UK ranges and vary by boiler make and region. No heat or hot water right now? Get an emergency heating engineer on the way fast.