Old Fuse Box: Do I Need To Upgrade?

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

Who fixes this

• Consumer unit replacement
• EICR

What it usually costs

Fuse Box Replacement Cost

£350–£800

EICR Cost

£100–£330

Questions people ask

Sources & References

1. IET: BS 7671 Guidance Publications
2. Electrical Safety First: Best Practice Guides
3. NICEIC: Householder Guidance
4. BS 7671: IET Wiring Regulations (18th Edition)