Consumer Unit or Fuse Box: What's the Difference, and Do You Need an Upgrade?

The box on your wall that controls the circuits in your home goes by several names depending on how old it is and who you’re talking to. Fuse box, fuse board, consumer unit, distribution board. They’re not all the same thing, and the differences matter if you’re planning electrical work or selling your property.

What’s a Fuse Box?

“Fuse box” is the colloquial term for older-style boards that use rewirable fuses or cartridge fuses to protect circuits. These were standard in UK homes up until the 1970s and into the 1980s.

When a circuit draws too much current, the fuse wire melts (or the cartridge blows), cutting power to that circuit. To restore it, the fuse needs to be replaced or rewired. Some older boards also had a main switch and very little else.

The critical limitation of old fuse boards is that they don’t have RCD protection. A residual current device (RCD) cuts the power within 30 milliseconds if it detects a current leak to earth. That speed of disconnection is what protects you from electric shock if a cable is damaged. Without it, a fault can be lethal before any conventional fuse blows.

What’s a Consumer Unit?

A consumer unit is the correct term for a modern fuse board. Instead of fuses, it uses miniature circuit breakers (MCBs) that trip automatically and reset with a switch. It also includes one or more RCDs, providing the shock protection that older boards lack.

Since 2016, Building Regulations have required consumer units in domestic properties to have metal enclosures rather than plastic, to reduce fire risk. If your consumer unit has a white plastic casing, it predates this requirement.

When Do You Need to Upgrade?

An old fuse board doesn’t automatically mean you need to replace it immediately. But there are specific situations where an upgrade becomes necessary or strongly advisable:

You’re having a full house rewire. A new consumer unit is always included in a full rewire. The two go together.

You’re having an EV charger installed. A 7kW home charger requires a dedicated 32-amp circuit with RCD protection. If your existing board can’t accommodate this safely, an upgrade or a dedicated consumer unit addition is required as part of the installation.

You’re adding solar panels or battery storage. Generation circuits need to be correctly integrated with your supply. An old fuse board can’t handle this safely, and most inverter manufacturers specify the board requirements in their installation documentation.

You’re selling your home. An Electrical Installation Condition Report (EICR) is increasingly expected by buyers and their solicitors. An old fuse board will almost always generate observations on the report, and some conveyancers push for an upgrade to be completed before exchange.

You’re having a significant extension built. New circuits for additional rooms need to be connected to the consumer unit. If the existing board is full or out of date, an upgrade is done as part of the extension electrical work.

What Does an Upgrade Involve?

For a straightforward consumer unit swap where the existing circuit wiring is in reasonable condition, the process is relatively quick. The old board is removed, the new dual-RCD consumer unit is installed, and all existing circuit cables are re-terminated into the new board. The installation is then tested and an Electrical Installation Certificate is issued.

For most properties, this is a half-day to full-day job.

Worth knowing: during testing, existing circuit wiring sometimes reveals faults that weren’t apparent beforehand, particularly on older installations. A good electrician will tell you upfront if anything comes to light during the job rather than pressing on regardless.

What Does a Consumer Unit Upgrade Cost?

In Derbyshire and the surrounding area, a consumer unit replacement typically costs between £400 and £650, including all testing and the certificate.

If the circuit wiring is found to have faults that require remedial work, that’s additional. But in many properties where the wiring is otherwise sound, a consumer unit swap resolves the compliance issue cleanly and at a predictable cost.

Is It Worth Upgrading as a Standalone Job?

If you have an old fuse board and you’re planning any significant electrical work in the next couple of years — an EV charger, an extension, a kitchen renovation — it usually makes sense to upgrade the board either as a standalone job now or fold it into the next project.

Running older wiring from a new, properly protected consumer unit is substantially safer than the original setup, and you avoid the disruption of two separate jobs.