Fuse Box vs Consumer Unit: Do You Need an Upgrade?

Short answer: "fuse box" is the older term for what's now called a consumer unit. Modern consumer units include RCD or RCBO protection that cuts power automatically if a fault is detected, which older rewireable fuse boxes don't have, and this is usually the main reason an upgrade is recommended.

What's actually changed

Older fuse boxes use rewireable fuses or simple MCBs (miniature circuit breakers) that protect against overload and short circuit, but don't protect against earth leakage, which is what causes electric shocks from a faulty appliance or damaged cable. Modern consumer units add RCD (residual current device) or RCBO protection on top of MCBs, which detects earth leakage and cuts power in a fraction of a second.

Signs your consumer unit is outdated

• A wooden-backed or black bakelite fuse box with visible rewireable fuses
• No RCD protection listed on the unit, or only one RCD covering every circuit in the house
• Frequent nuisance tripping, or no tripping at all even when it should
• Visible signs of scorching, heat damage or a burning smell near the unit

When an upgrade is typically required

A consumer unit upgrade is commonly needed as part of a full rewire, when adding a new circuit for an extension or outbuilding, following a failed EICR (Electrical Installation Condition Report), or where a landlord's insurer or mortgage lender specifically requires RCD protection. It's also often recommended proactively on older properties even without a specific trigger, given the safety improvement involved.

What the job involves

Replacing a consumer unit means isolating the supply, removing the old unit, fitting the new one with RCBOs for individual circuit protection, and testing every circuit before signing it off with an Electrical Installation Certificate. On a straightforward installation this is typically a one-day job, though older wiring occasionally reveals issues that need addressing at the same time.

Regulations, certification requirements and grant limits referenced here are correct at the time of publication and are reviewed and updated from time to time by government and local authorities. Always confirm the current position with a qualified, registered professional or your local authority before relying on it.