How do I know if my fuse box needs upgrading?

If it has rewirable fuses, no RCD test buttons, a wooden back, or cast iron switches, it needs upgrading. A modern consumer unit will have MCBs (switches) and at least one RCD with a test button.

Is it a legal requirement to upgrade my fuse box?

There is no law requiring homeowners to upgrade, but it is a legal requirement for rented properties to have a satisfactory EICR — and an old fuse box will almost certainly fail the inspection. It is also required under BS 7671 when any new circuits are added.

How long does a consumer unit replacement take?

A straightforward replacement takes 4–8 hours. The power will be off for most of that time, so plan accordingly. The electrician will also need to test every circuit in the property.

Will I need to rewire as well?

Not necessarily. If the existing wiring is in reasonable condition, a consumer unit upgrade can be done without rewiring. The electrician will check during testing and advise if any circuits need attention.

What is the difference between RCDs and RCBOs?

An RCD protects multiple circuits from earth faults, but a trip on one circuit takes out all circuits on that RCD. An RCBO combines RCD and MCB protection in one device, so each circuit is independently protected. RCBO boards cost more but are more convenient.

Caution

Updated 30 August 2026

Old Fuse Box — Do I Need To Upgrade?

Your fuse box is old and you are wondering whether it needs replacing with a modern consumer unit.

What would yours cost?

We'll tell you the price for this, then find a local electrician to do it.

on your first booking

Get my instant quote

What's happening?

An old fuse box (also called a fuse board) uses rewirable fuses or cartridge fuses rather than modern MCBs (miniature circuit breakers) and RCDs (residual current devices). These older boards lack the safety features of a modern consumer unit — specifically, they do not have RCD protection, which guards against electric shock from earth faults. If your fuse box has a wooden back, cast iron switches, or rewirable fuse carriers, it is almost certainly due for an upgrade.

What usually causes it?

Property has not been upgraded since it was built (often pre-1990s)
Fuse box still uses rewirable fuses with fuse wire
No RCD protection on any circuits
Board does not have enough ways for the number of circuits needed
Modifications have been made by adding external RCDs or additional fuse boxes

Is it dangerous?

An old fuse box is not immediately dangerous if the wiring is in good condition, but it provides significantly less protection than a modern consumer unit. Without RCDs, there is no protection against earth faults — the type of fault most likely to cause electric shock. Old rewirable fuses can also be fitted with the wrong rated fuse wire, defeating the overcurrent protection.

Can I fix it myself?

No. Consumer unit replacement involves work close to the incoming supply and should be carried out by a competent electrician. In England it is notifiable under Part P: a registered competent person can self-certify, or the work must follow the Building Control route.

When should you call an electrician?

Get a quote for a consumer unit upgrade if your fuse box has rewirable fuses, no RCD protection, a wooden back board, or is running out of space for circuits. It is also required when selling a property and may be flagged in a buyer's survey or EICR.

What will the electrician actually do?

Assess the existing installation and confirm suitability for upgrade
Remove the old fuse box and fit a new 18th Edition consumer unit
Install RCDs or RCBOs to protect all circuits
Test every circuit in the property (insulation resistance, earth fault loop impedance, RCD function)
Label all circuits clearly on the new board
Issue an Electrical Installation Certificate and notify Building Control