Most modern gas boilers last between 10 and 15 years, and a well-serviced one will reach the top of that range. Past about 12 years, repairs start costing more than they are worth, parts get harder to source, and efficiency has usually dropped enough that a new boiler starts paying for itself.
Not age, exactly. What kills boilers is the condition of the system around them.
A boiler pumping water full of sludge and corrosion debris is working against a restriction every day of its life. The heat exchanger runs hotter than it should, the pump works harder, and the whole thing wears out years early.
This is why a power flush and a magnetic filter are not upsells. A boiler fitted onto a filthy system will not last, and most manufacturers will not honour the warranty if it was not cleaned properly first.
Bills going up while nothing else changed. Efficiency drops as a boiler ages, so you burn more gas for the same heat.
Repeated breakdowns. Two callouts in a winter is a message.
Losing pressure regularly. Banging or kettling. Radiators taking an age to warm up. Error codes appearing.
And the quiet one: parts becoming hard to get. Once a manufacturer stops supporting a model, a repairable fault becomes a replacement anyway.
The rough rule: if the repair costs more than a third of a new boiler, and the boiler is over ten years old, replacing usually makes more sense.
But it depends on what has broken. A heat exchanger or a gas valve on an old boiler is a bad bet. A diverter valve on an eight-year-old boiler is worth fixing.
We will tell you which one you are looking at rather than defaulting to selling you a boiler.
If your boiler is on its last legs, this is the moment to think, not to panic-buy the same thing again.
If you are off the gas grid on oil or LPG, the Boiler Upgrade Scheme puts £9,000 towards an air source heat pump for eligible properties from 21 July 2026, against £7,500 for homes on mains gas. Another oil boiler will still be there in 2040.
Read our heat pump page before you commit, or our oil to heat pump guide if you are on oil.
Between 10 and 15 years for most modern condensing boilers. A well-serviced boiler on a clean system reaches the top of that range. One running on a sludged-up system will not.
As a rough guide, if the repair costs more than a third of a new boiler and the boiler is over ten years old, replacement usually makes more sense. It also depends what has failed: a heat exchanger on an old boiler is a bad bet, a diverter valve on a newer one is worth fixing.
Yes, materially. Sludge and corrosion debris restrict flow through the heat exchanger, which makes the boiler run hotter and work harder. Most manufacturers also require the system to be cleaned before a new boiler goes in, or the warranty does not stand.
It depends on the property and whether you are on mains gas. Off-grid homes on oil or LPG get a larger grant and a stronger running-cost case. We survey properly and give you an honest answer rather than a sales pitch.
We diagnose the actual fault before quoting to fix it. No jargon, no scare tactics.
