How long does a boiler last?

What actually wears a boiler out

Three things age a boiler faster than the calendar. Sludge is the big one: iron oxide from the radiators settles in the heat exchanger, makes the boiler work harder for the same heat, and eventually blocks or corrodes it. A magnetic filter and clean system water slow this to a crawl, which is why installers fit them as standard now.

The second is short cycling. An oversized boiler reaches temperature quickly, shuts down, cools and fires again, over and over, and every one of those cycles is thermal stress on the components. The third is simple neglect: an annual service is when small faults get caught while they are still small, and a boiler that has never been serviced usually shows it inside.

The signs a boiler is near the end

No single symptom means the end on its own, but a pattern is telling. Breakdowns arriving more than once a year. Radiators taking noticeably longer to warm. A pilot or flame that burns yellow rather than blue, which needs an engineer promptly for safety reasons. Banging or kettling noises from the heat exchanger. And energy use creeping up while nothing else in the house has changed.

Age matters alongside the symptoms because parts availability falls away. Manufacturers typically keep parts for around ten years after a model is discontinued, so a fifteen-year-old boiler can become unrepairable in practice even when the fault itself is minor.

When repairing stops making sense

A useful rule: if a repair costs more than about a third of a replacement, and the boiler is past ten years old, the money is usually better going towards the new one. A £400 repair on a twelve-year-old boiler that will need another £400 next winter is the expensive route to the same destination.

The other half of the sum is efficiency. A boiler from the mid-2000s running at around 80% costs meaningfully more in gas each year than a new one at 90%, so an ageing boiler has a running cost penalty on top of its repair bills. Replacement prices for most UK homes sit between £1,800 and £3,500 fitted, and you can compare boiler quotes from local installers to see where your job lands.

If the boiler still works and you are weighing the decision rather than facing a breakdown, start with a service. A good engineer will tell you honestly whether yours has years left, and what a new boiler costs in 2026 is there when the answer is no.