🔢 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 £2,000-2,500. So if a repair costs more than £1,000-1,250, a new boiler is likely better value.
A new combi boiler installed in London typically costs £2,000-2,500. So if a repair costs more than £1,000-1,250, 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
| Boiler Type | Supply & Install | Annual Saving vs Old Boiler |
|---|---|---|
| Standard combi (e.g. Worcester 4000) | £1,800 – £2,200 | £150 – £300/year |
| Mid-range combi (e.g. Worcester 8000) | £2,200 – £2,600 | £200 – £350/year |
| Premium combi (e.g. Vaillant ecoTEC) | £2,400 – £3,000 | £250 – £400/year |
| System boiler + cylinder | £2,500 – £3,500 | Varies |
A new A-rated boiler can pay for itself in energy savings within 7-10 years, while providing reliable heat with a 10-12 year warranty.
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.
FE Maintenance installs Worcester Bosch, Vaillant and Baxi boilers — all reliable brands with good parts availability and manufacturer warranties of 10-12 years. Worcester Bosch is consistently rated the most reliable brand in the UK. Call 020 8445 1303 for a free recommendation based on 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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