Boiler dies. Repair or replace? The rule of thumb is if the repair costs more than 50 percent of a new boiler and yours is over 10 years old, replace. But the real decision has more factors. Here is how to think it through honestly.

The age test

  • Under 7 years old: Almost always repair. It should be under warranty, and a modern boiler at 5 years old has 10+ more years in it.
  • 7 to 10 years: Case by case. See the cost test below.
  • 10 to 12 years: Repair only for cheap fixes (under £250). Otherwise strongly consider replacement.
  • 12+ years: Replace. Any significant repair is money down the drain on a boiler that will fail again soon.

The cost test

  • Repair under £200: Always fix, regardless of boiler age.
  • Repair £200 to £400: Fix if under 8 years old. Replace if over 10.
  • Repair £400+: Replace unless the boiler is under 5 years old.
  • Multiple recent repairs: Replace. Diminishing returns.

The efficiency test

Boilers pre-2005 (non-condensing) are 70 to 80 percent efficient. Modern A-rated condensing boilers are 90+ percent efficient. That is a 15 to 20 percent reduction in gas bills.

Average Leeds household gas bill 2026: £1,600 per year. 20 percent saving = £320 per year. A new boiler pays back its replacement premium in 6 to 8 years, sooner if you had frequent old-boiler repairs.

The reliability test

  • If your boiler has broken down 3+ times in 2 years, replace.
  • If it will not hold pressure, replace (the expansion vessel is usually done and other components follow).
  • If the same fault has recurred after a repair, replace.

The safety test

Some faults are non-negotiable replacements:

  • Cracked heat exchanger (carbon monoxide risk)
  • Failed flue seal on room-sealed unit
  • Corroded case allowing fume leakage
  • Gas leak that cannot be isolated to a valve or joint

Common repair costs

  • Diverter valve: £180 to £280
  • Fan: £220 to £340
  • Expansion vessel replacement: £180 to £250
  • PCB (main circuit board): £280 to £480
  • Pump: £220 to £320
  • Ignition assembly: £180 to £280

The honest conversation

Some engineers push replacement on any borderline job because it is a bigger sale. Others push repair because a callout is easier than a full install. Neither is right. The right answer depends on your specific boiler, its age, and how many faults it has had.

We tell you both prices side by side and let you decide. If we would replace it in our own house, we say so. If we would repair, same.