🔢 The 50% Rule — A Simple Guide
The most useful rule of thumb for the repair vs replace decision:
If the repair cost is more than 50% of a new boiler's cost — replace it.
A new combi boiler installed in London typically costs £2,000–£3,600 (with FE Maintenance, a combi swap is from £1,900). So if a repair costs more than about £1,000, a new boiler is likely better value.
A new combi boiler installed in London typically costs £2,000–£3,600 (with FE Maintenance, a combi swap is from £1,900). So if a repair costs more than about £1,000, a new boiler is likely better value.
But the 50% rule is just a starting point. You also need to consider the age of the boiler.
📊 Boiler Age vs Repair Decision
| Boiler Age | Repair Recommendation | Reason |
|---|---|---|
| Under 5 years | ✅ Always repair | Should still be under warranty |
| 5-8 years | ✅ Repair if under £400 | Many years of life left |
| 8-12 years | ⚖️ Depends on cost | Apply the 50% rule |
| Over 12 years | ⚠️ Consider replacing | Efficiency and reliability declining |
| Over 15 years | 🔄 Replace recommended | Parts becoming unavailable |
💷 New Boiler Costs in London 2026
| Job | FE Maintenance | Typical London range |
|---|---|---|
| Combi swap (old combi out, new combi in) | from £1,900 | £2,000 – £3,600 |
| New system boiler with hot water cylinder | from £2,500 | £2,800 – £6,000 |
| Conversion: tanks and cylinder to a combi | from £3,500 | Top of the range |
New boilers from FE Maintenance come with up to a 10-year warranty, a free quote on the phone and a fixed price before work starts. Our prices are the total — no VAT added. Not sure which type you need? See combi vs system boiler. For a full price breakdown, see boiler replacement cost in London.
Frequently Asked Questions
A well-maintained boiler should last 15-20 years. Boilers that are serviced annually typically last significantly longer than those that aren't. After 12-15 years, efficiency declines and parts become harder to source, making repairs more expensive.
A 10-year-old boiler can still have 5-8 years of life left if it's been well maintained. For repairs under £400, it's usually worth repairing. For repairs over £500-600, getting a quote for a new boiler makes sense — the energy savings from a modern boiler can offset the cost over time.
We recommend a boiler from a well-established manufacturer with good parts availability, sized correctly for your home. New boilers from FE Maintenance come with up to a 10-year warranty. Call 020 8445 1303 for a free quote on the phone and a recommendation for your home.
The government's ECO4 scheme provides free or subsidised boiler replacements for qualifying households on certain benefits. FE Maintenance can advise if you may be eligible. Call 020 8445 1303 for a free assessment.
A straightforward like-for-like combi boiler replacement typically takes one day. If the installation involves moving the boiler location, upgrading pipework, or changing from a system to a combi boiler, it may take 2 days. FE Maintenance will give you a timeline before starting work.
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