A consumer unit replacement swaps an old fuse box for a modern board with RCD or RCBO protection, and a surge protection device where required, installed and certified to BS 7671. It is often needed after an unsatisfactory EICR or before an extension or new kitchen. BritCertify replaces domestic consumer units across London from £299 inc. VAT and commercial boards from £799, priced after survey.
When does a fuse box need replacing?
A consumer unit should be replaced when it can no longer give the protection the installation needs, or when an EICR codes it as dangerous or potentially dangerous. Age alone is not the test: a modern board in good condition with proper RCD protection may need nothing more than relabelling.
The signs our electricians look for are:
- rewireable or cartridge fuses instead of circuit breakers;
- no RCD protection, or a single RCD covering every circuit so one fault blacks out the whole home;
- scorch marks, a burning smell, buzzing, or a board that feels warm to the touch;
- a C1 or C2 observation against the board on an EICR;
- no spare capacity for an extension, a new kitchen, an electric shower or an EV charger;
- a cracked or damaged enclosure, or a cover that no longer closes.
If your board is in good order, we will say so. Sometimes adding protection to individual circuits is all that is needed.
What does a modern consumer unit include?
In a home, a new consumer unit has a non-combustible enclosure, 30 mA RCD protection for the circuits that need it, and a surge protection device where one is required. BS 7671 requires domestic consumer units to be made of non-combustible material or housed in a non-combustible enclosure, which in practice means a steel board.
| Component | What it does |
|---|---|
| Main switch | Isolates the whole installation for maintenance or in an emergency |
| RCBOs | Combine overload protection and 30 mA RCD protection on each circuit, so a fault trips only the circuit concerned |
| Dual RCD arrangement | Two RCDs, each protecting a group of circuits; lower cost, but one fault can switch off several circuits at once |
| Surge protection device (SPD) | Limits transient overvoltages, for example from lightning or switching on the network, that can damage electronics |
| Labelling and circuit chart | Identifies every circuit so occupants and future electricians can isolate safely |
BS 7671 requires 30 mA RCD protection for socket outlets, for lighting circuits in homes and for cables concealed in walls without other protection. It also requires the risk from transient overvoltages to be assessed on new work, and we explain on survey whether an SPD is required for your property. For rented homes we generally recommend RCBOs: a tenant’s faulty toaster then trips one kitchen circuit rather than the fridge freezer and the lights.
Does replacing a consumer unit need Part P notification?
Yes. In homes in England, replacing a consumer unit is notifiable work under Part P of the Building Regulations. Our electricians notify it through their NICEIC or NAPIT registration, so you do not need a separate building control application, and a Building Regulations compliance certificate is issued to the householder once the work is registered.
You also receive an Electrical Installation Certificate (EIC) with a schedule of test results for every circuit connected to the new board. Keep both documents together: buyers’ solicitors, letting agents and future electricians will ask for them, and landlords can send the EIC as written confirmation that EICR remedial work is complete.
Part P applies to dwellings only. Commercial distribution boards are still designed, installed and certified to BS 7671 with an EIC on completion, but without Part P notification. Electrical inspections are carried out by NICEIC / NAPIT registered electricians, qualified to BS 7671.
Why is testing before the swap so important?
Because a new board with RCD protection exposes faults that old fuses tolerated for years. Before connecting anything, our electrician tests the existing circuits for insulation resistance, continuity and polarity, and checks the earthing arrangement and main protective bonding to the gas and water pipes.
The faults this uncovers include damp in cables, nails or screws through cables, and borrowed neutrals, where one circuit’s neutral returns through another. Each of these will trip an RCD repeatedly. They have to be put right before the circuit is connected, so we tell you what we have found and agree the cost before continuing. If a circuit cannot be repaired the same day, it is left safely disconnected and labelled, and we explain the options.
The supply also has to be isolated to change the board. Where there is no isolator between the meter and the fuse box, the main fuse at the cut-out has to be withdrawn, which can mean arranging a visit from UK Power Networks, the network operator for London, first. We check this on survey so it does not hold up the job.
What do we find when replacing boards in London homes?
- Victorian conversions: boards in shared hallways or basements, long meter tails, and lighting circuits that still cross between flats created from a single house.
- Older houses: occasional runs of rubber-insulated or lead-sheathed cable still in use. These are tested carefully, and where they have deteriorated we recommend rewiring those circuits rather than connecting them to a new board.
- Ex-local authority and mansion block flats: rewireable fuse boards with no RCD protection, and main protective bonding that is missing or undersized.
- HMOs: a separate landlord’s board feeding communal lighting, the fire alarm and emergency lighting. We keep those supplies on clearly labelled circuits so they are not switched off by mistake.
When should landlords schedule the replacement?
Ideally between tenancies, or promptly within the 28-day window after an unsatisfactory EICR. An empty property means nobody is left without power for the day, and any faulty circuits found during pre-installation testing can be repaired without working around a tenant. If the board is coded C2 and the property is occupied, do not wait for the tenancy to end: the 28-day deadline still applies, so give notice and book straight away.
How should you prepare for the work?
Expect the power to be off for most of the day on a typical domestic job. To keep things smooth:
- tell tenants in writing, and ask them to keep fridge and freezer doors shut while the power is off;
- clear the area around the board and any loft or cupboard access;
- in flats, check whether the meter or board sits in a communal area that needs freeholder or managing agent access;
- be ready to reset clocks, timers, heating controls and alarm panels afterwards;
- send us your latest EICR if the replacement is a remedial item, so we can quote against it.
Domestic replacements start from £299 inc. VAT and commercial boards from £799 inc. VAT, with the final price confirmed after survey. Bonding upgrades and SPDs are itemised in your quote, and any faults found during testing are priced before work continues. You can request a survey online, and business owners may also need a commercial EICR.
Consumer unit replacement prices in London (inc. VAT)
| Option | Price (inc. VAT) | Notes |
|---|---|---|
| Domestic consumer unit replacement | From £299 | Final price confirmed after survey |
| Commercial distribution board replacement | From £799 | Final price confirmed after survey |
Prices include VAT. The final price is confirmed after a survey of the existing board, earthing and circuits. Central London parking or Congestion Charge may be added; we always confirm before booking.
Book this serviceWhat's included
- Survey and fixed quote before work starts
- Metal consumer unit for domestic properties
- RCD or RCBO protection to BS 7671
- Surge protection device where required
- Testing of every circuit before and after the swap
- Clear circuit labelling and chart
- Electrical Installation Certificate
- Part P notification for domestic work
How it works
Survey
We look at your existing board, earthing, bonding and circuits, then confirm a fixed price and anything that must be fixed first.
Pre-installation testing
On the day, circuits are tested before connection so hidden faults are found and dealt with, not left to trip the new RCDs.
Installation
The new consumer unit is fitted, each circuit connected to the right protective device, and the board fully labelled.
Certification
You receive an Electrical Installation Certificate and, for homes, Part P notification with a Building Regulations compliance certificate to follow.
Fuse Box Replacement: frequently asked questions
How much does a fuse box replacement cost in London?
Domestic consumer unit replacements start from £299 inc. VAT and commercial distribution boards from £799 inc. VAT. The final price is confirmed after a survey and depends on the number of circuits, whether you choose RCBOs or a dual RCD board, whether an SPD is needed, and any bonding upgrades. Central London parking or Congestion Charge may be added; we always confirm before booking.
How long does a consumer unit replacement take?
Most domestic replacements are completed within a working day, with the power off for much of it. The time depends on the number of circuits, the condition of the existing wiring and whether faults turn up during pre-installation testing. Commercial boards are planned around trading hours and may be split across visits to keep shutdowns short.
Do I need a metal consumer unit?
For a new or replacement consumer unit in a home, yes. BS 7671 requires domestic consumer units to be enclosed in non-combustible material, which in practice means steel. An existing plastic board is not automatically unsafe and will not necessarily fail an EICR on that point alone, but any replacement must meet the current requirement.
Why does my new RCD keep tripping?
Usually because the RCD has found a fault the old fuses could not detect, such as damp in a cable, a faulty appliance or a borrowed neutral. Unplug everything on the affected circuit and reset it. If it holds, plug items back in one at a time to find the culprit. If it trips with nothing connected, the circuit needs testing.
What certificates will I receive?
You receive an Electrical Installation Certificate with a full schedule of test results. For homes in England, the work is also notified under Part P of the Building Regulations, and a Building Regulations compliance certificate follows. Landlords can use the EIC as written confirmation that consumer unit remedial work from an EICR has been completed.
Can a consumer unit be replaced without rewiring?
In most cases, yes. A new board can be fitted to the existing wiring as long as the circuits pass insulation resistance and continuity tests. Where testing reveals badly deteriorated or very old cabling, such as rubber-insulated wiring, we tell you before installing and explain whether individual circuits or a full rewire are needed.
Sources and official guidance
Written and checked by the BritCertify technical team. Last reviewed 6 October 2026.