The short answer
Repair the boiler if it is reasonably young, the fault is a one-off and parts are available. Consider replacing it if it is older and breaking down repeatedly, parts are becoming hard to get, it has had a major failure such as a heat exchanger, or it is an old non-condensing model. An honest engineer should tell you which makes more sense for your boiler.
When a repair makes sense
Most boiler faults are routine. Pumps, diverter valves, sensors and fans wear out and can be replaced without touching the rest of the boiler. If your boiler has been reliable up to now and has been serviced regularly, one repair is usually the sensible choice.
- The boiler is still within or close to its warranty period.
- It has been reliable and serviced every year.
- The fault is a common, replaceable part.
- The repair cost is small compared with a new boiler.
Signs it may be time to replace
Some patterns suggest money spent on repairs will not last. If several of these apply, it is worth getting a replacement quote alongside the repair quote:
- Repeated breakdowns over the last year or two.
- A major component failure such as the heat exchanger.
- The manufacturer no longer supplies parts for the model.
- An old non-condensing boiler, which is far less efficient than modern condensing models.
- Hot water that no longer keeps up with how the household uses it.
- Rising energy bills with no change in how you use the heating.
Efficiency: the hidden cost of keeping an old boiler
Since 2005, new gas boilers fitted in England and Wales have had to be high-efficiency condensing models. Older non-condensing boilers lose much more heat up the flue. That lost heat is paid for every month, which is why replacing a very old boiler can make sense even when a repair is possible.
Questions to ask your engineer
A good engineer will explain the options rather than push one. Useful questions include:
- What exactly has failed, and why?
- Is this likely to be the start of more failures?
- Are parts still readily available for this model?
- What would a suitable replacement be for my home?
- Would my system need other work, such as a flush, if I replace the boiler?
If you decide to replace
A replacement starts with a survey so the new boiler is sized for your home. For many homes a combi is the right choice; for larger homes with several bathrooms, a system boiler with a cylinder can be better. Our installation guide explains how long the work takes, and boiler finance can spread the cost if that helps.
If you decide to repair
Keep up with annual servicing, keep an eye on system pressure and fit a magnetic filter if there is not one already. These simple steps help an older boiler last longer and make breakdowns less likely.
Combi, system or regular: choosing a replacement type
If replacement wins, the type of boiler matters as much as the brand. A combi heats water on demand straight from the mains, needs no tanks and suits most flats and homes with one or two bathrooms. A system boiler stores hot water in a cylinder, which suits homes where several showers run at once. A regular, or heat-only, boiler works with a cold water tank in the loft and a cylinder, and can be the simplest swap in older homes with that setup already in place.
Switching type is possible but adds work, so it is best decided at survey after the engineer has checked mains pressure, flow rate and how many people use hot water at the same time.
Frequently asked questions
Is it worth repairing an old boiler?
It can be, if the fault is minor and the boiler has otherwise been reliable. If it is breaking down often or parts are hard to find, replacement is usually better value.
What is the most expensive boiler repair?
Heat exchanger failure is typically one of the costliest repairs, and on older boilers it is often the point where replacement makes more sense.
Will you tell me honestly if a repair is not worth it?
Yes. We explain the fault and the options, and leave the decision to you.
Can I spread the cost of a new boiler?
Yes, boiler finance is available. See our boiler finance page for details.