The average gas boiler lasts 12–15 years. Some fail at 10 years; others run reliably for 20+ years. The difference comes down to three factors: brand, annual servicing, and system condition.
Lifespan by brand (average)
- Viessmann: 15–20+ years
- Worcester Bosch: 12–18 years
- Vaillant: 12–18 years
- Ideal / Baxi: 10–15 years
- Budget brands: 8–12 years
The biggest factor: annual servicing
A boiler that is serviced every 12 months will consistently outlast one that isn't. Annual servicing catches small issues (limescale, worn seals, dirty burners) before they cause expensive failures.
System water quality matters too
Black sludge (magnetite) is the most common cause of premature boiler failure. A magnetic filter on the return pipe and annual inhibitor top-ups dramatically extend boiler life by preventing this build-up from reaching the heat exchanger.
When is it time to replace?
Once a boiler is over 12 years old and requiring regular repairs, replacement is usually more cost-effective than continued maintenance. A modern A-rated boiler can cut heating costs by 20–30% compared to an older G-rated unit.