It's tempting to want a simple rule ("replace after 10 years", say), but that's not how it really works in practice. We've repaired 15-year-old boilers that had years of life left, and seen 6-year-old boilers where replacement made more sense. The honest answer comes from weighing a few factors together, not any single one.
Boiler age
Most boilers are designed to last 10–15 years, and parts availability tends to drop off for older, discontinued models. Age alone isn't a reason to replace, but it does affect whether a part is even obtainable.
What's actually failed
A failed pump, PCB, or valve is usually a straightforward, worthwhile repair on a boiler that's otherwise sound. A cracked heat exchanger — the core of the boiler — is a different story, and often the point where replacement becomes the more sensible option regardless of age.
Repair history
One repair doesn't tell you much. Three unrelated call-outs in the last two years does — it's a pattern worth factoring in, not just the cost of this specific fix.
Cost of the repair vs. a new boiler
As a rough guide, if a repair is going to cost more than a third of the price of a straightforward replacement, it's at least worth discussing both options properly rather than assuming repair is automatically cheaper long-term.
Efficiency
A boiler more than 10–15 years old is very likely significantly less efficient than a current model, which affects running costs regardless of whether it's currently faulty.
Our honest approach
We'll tell you plainly which way we'd lean and why — but the decision is yours. We're not on commission for pushing new boilers, and a repair that gets you another few reliable years is often the right call. For real pricing on both sides of that decision, see our repair cost guide and our Worcester and Baxi installation pricing.