Fuse box or consumer unit? How to tell what you have

They are the same thing: the box where your electricity arrives and splits into circuits. "Fuse box" is what it was called when it contained actual fuses; "consumer unit" is the current term. Which matters, because if yours genuinely still contains fuses, that tells you something — and you can work out which of four generations you have in about thirty seconds, without opening anything.

Identify yours from the outside

Look at the front of the board. Do not open it, and do not remove the cover — you do not need to.

The quickest single tell is the test button count. None means no RCD protection. One or two means split-load. One per circuit means you already have the good arrangement.

Why the box being metal is a rule, not a fashion

A modern consumer unit in a home has to have a non-combustible enclosure, which in practice means steel. The reasoning is specific: if a connection inside the board works loose and overheats, the resulting fire should stay inside the box rather than escaping into the fabric of the building. A plastic board cannot make that promise.

That does not make your plastic board illegal — it complied when it was installed, and compliance is judged against the standard of the day. What it does is date the installation, which is useful information: a plastic board tells you roughly when the electrics were last touched, and therefore what era the circuits behind it are likely to be from.

The difference that actually matters: RCD vs RCBO

This is the one thing worth understanding before anyone quotes you, because it is the decision you will be asked to make and the one most likely to be made for you by default.

That last row is worth dwelling on if your current problem is a board that trips for no obvious reason. Every modern appliance leaks a tiny, entirely legal amount of current to earth; put thirty of them behind one RCD and the total can sit just under the threshold until the dishwasher starts. Nothing is broken — the board is arranged badly. Full diagnosis in why an RCD keeps tripping.

Do you need a new one?

If you let the property, or it is an HMO

Two things change. First, the statutory inspection interval applies — at least every five years, with the report going to the tenant, and a maximum penalty that rose to £40,000 in May 2026. See landlord electrical safety certificate.

Second, and less well known: arc fault detection devices are mandatory in houses in multiple occupation. Regulation 421.1.7 requires AFDDs on single-phase final circuits supplying socket-outlets up to 32 A in higher-risk residential buildings, HMOs, purpose-built student accommodation and care homes. In an ordinary house they are recommended, not required. If you let an HMO and are replacing the board, this is a requirement and it affects the price — raise it before the quote rather than after.

What to do next

1. Count the test buttons. That is your generation.
2. Photograph the board, front and the label if there is one.
3. If nothing is wrong, do not rush. A working dual-RCD board is not an emergency.
4. If something is tripping, diagnose before you buy.
5. If you are replacing it, specify all-RCBO explicitly and get the difference in writing.
6. If the circuits are of unknown condition, an EICR first tells you whether the board is really the priority or whether the wiring is.

Prices, what legitimately adds to them, and what certificates you should end up holding are all on consumer unit replacement cost. A board change is notifiable under Part P, so check the contractor on the Registered Competent Person Electrical register before booking.