Heating
Repair or replace your boiler?
If your boiler is a condensing model, a new one will use little less gas, so a reasonable repair is often the cheaper choice. Safety, parts and repeated breakdowns can change that.
Updated 2 October 2026 · energy.org.uk editorial team
The short answer
Gas and LPG boilers fitted since 1 April 2005, and oil boilers since 2007, have had to be condensing. A working condensing boiler is already close to the efficiency of a new one, so replacing it saves little fuel. An older, non-condensing boiler is less efficient, but the saving still has to cover the extra cost of replacing it.
The repair or replace calculator compares your two quotes with any gas saving.
When replacing is usually right
- A Gas Safe registered engineer says the boiler is unsafe or cannot be repaired safely.
- Parts are no longer available.
- It has broken down repeatedly and the repair costs are adding up.
- You are planning another heating change soon, such as a heat pump, so a large repair would be wasted.
Check
What to check first
- Is it condensing? Condensing boilers have a plastic flue and a small waste pipe running to a drain.
- What exactly is the fault, and whether the repair comes with a guarantee.
- What the replacement quote includes: removal of the old boiler, a system flush, controls and the warranty.
- Your yearly gas use, from your bill, rather than a typical figure.
Do
Practical next steps
- Get a written repair quote and at least one replacement quote.
- Enter both in the repair or replace calculator.
- If you replace, consider whether a heat pump would suit your home; see the heat pump calculator and the Boiler Upgrade Scheme grant.
- Whatever you choose, lower the boiler's flow temperature to save gas; see heating controls and flow temperature.
Take care
Important limitations
- The calculator compares fuel savings only. It leaves out future repairs, servicing and warranty cover.
- Older boilers vary in efficiency. Without your boiler's own figure, the calculator shows two illustrations rather than a single answer.
- Only a Gas Safe registered engineer should work on a gas boiler.