The short answer
If your boiler is fairly young, has been reliable until now and the fault is a single part, repairing it usually makes sense. If it is old, breaks down repeatedly or needs parts that are hard to get, a new combi is usually the better use of your money. Age, repair history and the nature of the fault matter more than any one symptom. The prices other homeowners actually paid are shown separately on this page, so use this guide to decide which route suits you, then compare quotes.
How they differ
Boiler repair means a Gas Safe registered engineer finds the fault and fixes or replaces the failed part. Common faults include a broken diverter valve, a failed pump, a faulty thermostat or sensor, a blocked condensate pipe, low pressure caused by a leak, or ignition problems. The rest of your heating system stays as it is, and the work is often finished in a single visit.
A new combi means removing the old boiler and fitting a combination boiler, which heats radiator water and provides hot water on demand without a hot water cylinder or cold water tank. It is a bigger job. The installer may need to move pipework, fit a new flue, connect the condensate drain, add a filter and install new controls. If you currently have a regular or system boiler with a cylinder, switching to a combi is a larger change than swapping like for like.
A combi is not right for every home. It depends on mains water pressure and flow, and a household with several bathrooms in use at once may find a single combi struggles to keep up.
Cost: what makes each more or less expensive
A repair is almost always cheaper on the day than a new boiler. A new boiler is a much larger one-off expense, though it removes the risk of further repair bills for some time.
What pushes a repair up or down:
- The part. Small, common parts are cheaper than major components such as a heat exchanger or main circuit board.
- Availability. Parts for older or less common models can be costly or hard to source, which adds time and money.
- Labour and access. A boiler in a cupboard or loft takes longer to work on than one on an open wall.
- Diagnosis. Intermittent faults can take longer to track down.
- Repeat visits. Several small repairs over a year or two can add up to a large share of the cost of a replacement.
What pushes a new boiler up or down:
- Boiler choice. Output, brand, warranty terms and built-in features all affect the price.
- Scope of work. Swapping a combi for a combi in the same spot is simpler than converting from a regular system, which may mean removing a cylinder and tanks.
- Flue and pipework. Moving the boiler or running a longer flue adds labour and materials.
- System condition. Old radiators and pipework may need cleaning or a powerflush, and a magnetic filter is a sensible addition.
- Controls. A smart or programmable thermostat costs more than a basic one.
- Running costs. A modern boiler is generally more efficient than an old one, so it may cost less to run, but this is a long-term saving rather than a way to recover the purchase price quickly.
Lifespan and upkeep
A repair only extends the life of the boiler you already have. A fixed part does not make the rest of the boiler any younger, so other components may fail later. Boilers that have been serviced regularly tend to last longer and are cheaper to keep going. Ask the engineer to be honest about how worn the rest of the unit looks.
A new combi starts with a clean slate. Most come with a manufacturer's warranty, and the terms often depend on the boiler being installed by an approved installer and serviced regularly. Read the conditions before you buy, because missing a service can invalidate cover.
Whichever you choose, an annual service is worth having. It helps catch problems early, keeps the boiler running efficiently and is part of looking after your safety. A carbon monoxide alarm should be fitted near any gas appliance.
When to choose Boiler repair
Repair is the better choice when:
- The boiler is relatively young and has a good service history.
- The fault is clear, limited and involves a readily available part.
- This is the first or second fault, not part of a pattern.
- You are planning to move soon and do not want to spend heavily on the heating.
- Your current setup suits you, and a combi would not suit your water pressure or household needs.
- You need heat and hot water quickly and cannot arrange a full installation straight away.
It can also be a sensible stopgap if you want to spread the cost, as long as the engineer thinks the boiler is safe to keep running.
When to choose New boiler
A new combi is the better choice when:
- The boiler is old and the engineer says parts are scarce or no longer made.
- Repairs are becoming frequent, so you are paying for call-outs on a regular basis.
- The fault is major, such as a failed heat exchanger, and the repair would cost a large share of a replacement.
- The boiler is inefficient, noisy or struggling to heat the house.
- An engineer has condemned it as unsafe. Do not keep using a boiler that has been marked as dangerous.
- You want to free up space by removing a hot water cylinder and tanks, and your mains water supply can support a combi.
If you do replace, the work must be carried out by a Gas Safe registered installer. Building regulations apply to boiler replacement, and a registered installer will normally deal with notifying this for you. Planning permission is not usually needed for a like-for-like swap, but a new flue position or a listed building or conservation area could change that, so check with your installer or local council.
Questions to ask a tradesperson
- Are you Gas Safe registered, and can I see your ID?
- What exactly is the fault, and how confident are you in the diagnosis?
- Is the part available, and how long will it take to get?
- How old is my boiler, and how much life do you think it has left?
- If I repair it, what else is likely to fail next?
- Is a combi suitable for my home, given the water pressure and the number of bathrooms?
- Does the quote include removal of the old boiler, a filter, flue work, controls and making good?
- What warranty comes with the repair or the new boiler, and what are the servicing conditions?
- Can you give me a written, itemised quote for both options so I can compare them?