About a third of the people who call us about a "failing fuse board" don't actually need a new one. The other two-thirds absolutely do — and waiting makes it worse. Here's how to tell which camp you're in before you book anyone.
Five signs you probably need a new consumer unit
- Rewirable fuses. If you still have ceramic wire fuses rather than switches, your board predates the 17th Edition and almost certainly predates RCD protection. Time to go.
- A plastic enclosure on the main switch. The 18th Edition requires metal enclosures in domestic installations, driven by post-Grenfell fire research. Plastic boards aren't illegal, but they're non-compliant for new work.
- A single 30 mA RCD covering the whole house. One fault anywhere kills every circuit. Modern RCBO boards isolate faults to the affected circuit only.
- Discoloration or a burning smell near the busbar. This is a loose connection slowly roasting itself. Replace now, not next month.
- The main switch gets warm. Not hot, not dangerous, but noticeably warm under normal load is a sign that the board is struggling. Pair this with repeated nuisance trips and it's time.
Five signs that aren't (always) the board
- "My lights flicker when the kettle goes on." Usually a voltage-drop issue on a long ring main, not the board. Diagnose the circuit first.
- "My RCD tripped once last Tuesday." RCDs trip for real reasons. One trip in six months is almost always an appliance. Two or three in a week is worth investigating.
- "I can hear a buzzing sound." Most 50 Hz hum from a board is harmless — loose laminations, ageing MCBs. If it's sudden and new, investigate. If it's been there for years, it's likely fine.
- "The previous owner had an EICR done and it said C3 'consumer unit not to 18th Edition'." C3 means "improvement recommended" — not dangerous, not urgent.
- "I'm adding an EV charger and I've been told I need a new board." Sometimes true, often not. A proper load calculation usually shows headroom. Get a second opinion.
The cost conversation
A like-for-like 18th-Edition upgrade with RCBOs is £495–£795 for most Watford homes. Larger houses or ones needing a main earth upgrade at the same time land between £800 and £1,200. Anyone quoting under £400 is either going to cut corners or come back with extras.
It's a one-day job and every install we do is Part P notified and signed off with a BS 7671 Electrical Installation Certificate. If you're on the fence, book a survey — we don't charge for it and we'll tell you honestly if the existing board can wait another five years.
