Rewireable fuse boards — the kind with porcelain or ceramic holders and a thin piece of fusewire strung between two brass screws — were standard in British homes right up to the late 1980s. They were never great, but for decades there was no legal obligation to replace them. That changed with the 18th Edition of BS 7671 (the UK wiring regulations), and the growing insistence of mortgage lenders, insurers, and building surveyors across Somerset on seeing an up-to-date consumer unit before a sale can proceed.
The good news: if you have a rewireable board, upgrading it to a modern all-RCBO 18th Edition consumer unit is a single-day job. No replastering. No replumbing. In most homes it is done in four to six hours, and you leave with a full Electrical Installation Certificate (EIC) and automatic Building Control notification through our NAPIT registration.
Is Your Board Due an Upgrade?
Most people already know something is wrong before they call us. But for those who are unsure, here are the five situations where an upgrade is not just beneficial but necessary.
1. You have rewireable fuses
Open your consumer unit. If you see a row of ceramic or Bakelite holders with a thin wire threaded through — that is a rewireable fuse. When the fuse blows, you re-thread a new piece of wire and reset it. The problem is not nostalgia: it is that these boards have no RCD (Residual Current Device) protection whatsoever. An RCD cuts power in 40 milliseconds when it detects current leaking to earth — fast enough to save your life if you drill into a live cable. A rewireable board offers no such protection.
2. You have a wooden-backed board
Some older boards — often from the 1960s and 1970s — are mounted on a timber backing board rather than enclosed in a housing. Timber is combustible. Since the 16th Edition of the wiring regulations, all new consumer unit enclosures have been required to be non-combustible (now mandated as steel or equivalent under the 18th Edition). A wooden-backed board does not meet this standard and will receive a C2 code — potentially unsafe — on any Electrical Installation Condition Report (EICR).
3. No RCD protection on socket or bathroom circuits
Even some more modern boards — dual RCD split-load units from the early 2000s — may not provide RCD protection on every circuit. If your sockets, bathroom lighting, or outdoor circuits are not RCD-protected, you are not compliant with the 18th Edition. This matters if you are renting out a property: landlords in England and Wales are required by law to have an EICR carried out every five years, and an unprotected circuit will flag immediately.
4. Tripping problems that keep coming back
An RCD or breaker that trips repeatedly — especially one that trips even with all appliances unplugged — is telling you something about the state of the circuit or the board itself. Older RCDs become progressively more sensitive with age and will nuisance-trip at progressively lower fault currents. Sometimes the right fix is not chasing faults around the house but replacing the board entirely, at which point all that sensitivity disappears with the old unit.
5. You are selling or remortgaging
Mortgage surveyors in Wells, Bath, Frome, Shepton Mallet, and across Somerset are now routinely flagging old or non-compliant consumer units as a condition of sale. A lender will not lend on a property with a rewireable board or an unenclosed installation. Sorting it out before you go to market is always cheaper than renegotiating mid-sale — and a current EIC in the vendor's pack is a positive selling point.
Not sure if your board qualifies?
Book a £99 fuse board health check. We inspect, advise, and credit the £99 against your upgrade if you go ahead.
What You Get With an 18th Edition RCBO Upgrade
We specify an all-RCBO board for the vast majority of our domestic upgrades. Here is what that means in practice.
- Individual RCBO on every circuit — an RCBO (Residual Current Breaker with Overcurrent protection) combines the function of an RCD and a MCB in a single device. If a fault develops on one circuit, only that circuit trips. With an older split-load board, a single RCD covers multiple circuits — one faulty appliance on the ring main can take out half the house. With individual RCBOs, everything else stays on.
- Type 2 Surge Protection Device (SPD) — the 18th Edition introduced a requirement to consider SPD installation in all new and upgraded consumer units. An SPD absorbs transient voltage spikes — from nearby lightning strikes or switching events on the network — before they reach your appliances and wiring. We include a Type 2 SPD as standard.
- Non-combustible metal enclosure — all our boards are housed in a steel consumer unit enclosure. If a breaker were ever to fail internally, the steel box contains the fault and prevents it from spreading.
- Fully labelled circuits — every breaker is labelled before we leave. Upstairs lights, downstairs sockets, cooker, shower, immersion, garage — you know exactly what controls what.
- Earth bonding verified — during the upgrade we check and verify the main protective bonding to your gas and water services, and to any structural steel. If the bonding is undersized or missing, we make it right as part of the job.
- Full test schedule — every circuit is tested for insulation resistance, earth fault loop impedance, RCD trip time, and polarity before we issue your EIC. Nothing is left on assumption.
What Does a Consumer Unit Upgrade Cost in 2026?
Prices depend on the number of circuits, whether any remedial bonding is needed, and access to the existing installation. As a guide:
| Board Type | Typical Fitted Cost | Best For |
|---|---|---|
| All-RCBO 18th Edition (up to 12 ways) | From £450 | 2–3 bed property, straightforward installation |
| All-RCBO 18th Edition (up to 16 ways) | From £550 | 3–4 bed property with garage or outbuilding |
| All-RCBO with SPD + bonding remedials | From £650 | Older property requiring earth bonding update |
| Large property / extended installation | From £850 | 5+ bed, multiple sub-boards, complex wiring |
All prices include supply and fit of a new metal consumer unit with individual RCBOs, a Type 2 SPD, full test schedule to BS 7671:2018, an Electrical Installation Certificate, and NAPIT Part P notification to Building Control — at no extra cost. Our £99 fuse board health check is credited in full against the upgrade cost, so if you have already booked a check and decide to go ahead, you pay only the difference.
Read what our customers across Somerset say about the process on our testimonials page — the upgrade is consistently one of the jobs homeowners tell us they wish they had done sooner.
Timeline: What Happens on the Day
A standard consumer unit upgrade takes four to six hours from arrival to completion. Here is the sequence:
- Morning arrival and assessment — we count circuits, check the existing board, inspect earthing and bonding, and confirm the scope. Any unexpected work (e.g. missing bonding, deteriorated tails) is flagged before we start.
- Power off — we isolate at the meter and remove the old board. If you have a rewireable unit, we photograph it for records. The power will be off for the duration of the installation — plan for a few hours without it.
- New board installed — the metal enclosure is fixed, the individual RCBOs are populated and the circuits are landed. The SPD is wired in at the incoming supply.
- Testing — every circuit is tested in full with a calibrated multifunction tester. RCD trip times, insulation resistance, loop impedance, and polarity are all recorded on the test schedule.
- Circuits labelled, documentation issued — you receive your Electrical Installation Certificate before we leave. We submit the job to NAPIT and Building Control automatically — there is nothing you need to do.
Part P Notification Included
A consumer unit replacement is a notifiable job under Part P of the Building Regulations. As NAPIT-registered contractors we self-certify and register every board we install with your local Building Control authority. You receive a NAPIT Completion Certificate in addition to the EIC — invaluable documentation for any future sale or remortgage. This is included in the price; we do not charge separately for notification.
Domestic Electrical Work in Somerset
Consumer unit upgrades are one of the core services we carry out across Somerset as part of our domestic electrical offer. Whether you are in Wells, Radstock, Midsomer Norton, Castle Cary, or a rural property outside Bruton, the process is the same: one day, fully documented, with no disruption beyond the planned power-off window.
If you are unsure whether your board needs replacing, our £99 fuse board health check includes a full visual and functional inspection, an RCD trip-time test, and a written report with our recommendation. There is no obligation to proceed — and if you do, the £99 comes straight off the upgrade price.