Consumer units explained: types and how to choose

The consumer unit is the quiet hub of a building's electrics - the modern fuse board where the incoming supply splits out to every circuit, and where the protection that keeps those circuits (and the people using them) safe all lives. Most people never think about it until something trips, but if you're specifying one for a refurbishment, a rental or a commercial fit-out, a little understanding goes a long way.

One thing to say plainly up front: choosing a consumer unit is something you can do informed; fitting or replacing one is not a DIY job. It's notifiable work under the Building Regulations and must be carried out by a competent, registered electrician. This guide is about understanding what you're buying and why - the installation itself belongs with a professional.

What a consumer unit actually is

A consumer unit - the term that's largely replaced "fuse box" - is the enclosure that receives the main supply and distributes it around the building as separate circuits: lighting, sockets, the cooker, the shower and so on. Inside, a main switch lets you isolate everything at once, a busbar feeds power along the unit, and a row of protective devices sits on a DIN rail, one or more guarding each circuit. Larger commercial installations use the same idea on a bigger scale and call it a distribution board.

The protective devices are the important bit, and they come in a few forms - MCBs for overload and short circuit, RCDs for earth faults and shock protection, RCBOs combining both in one module, and surge protection (SPDs) against voltage spikes. We won't relitigate the differences here; our guide to circuit breakers covers how MCBs, RCDs and RCBOs compare, and you can browse the devices themselves in the circuit breakers range.

The main types

Current best practice leans towards protecting each circuit individually - typically a board populated with RCBOs - so that a fault on one circuit doesn't plunge half the building into darkness. Your electrician will specify the arrangement that suits the installation and the current edition of the wiring regulations (BS 7671, the 18th Edition), but it helps to know the language when you're comparing options.

What to consider when choosing

A handful of things shape the right unit. First, the number of ways - the module positions for circuits - with enough spare capacity to add a circuit later without starting again; a board that's full on day one is a false economy. Then the type of protection: individual RCBO protection is increasingly the norm for resilience, and surge protection is worth designing in. For domestic use, note that consumer units are now specified with a non-combustible (metal) enclosure, which is why you'll rarely see the old plastic boards fitted today. Match the main switch rating and the overall board to the supply and the load, and for a commercial site think in terms of a three-phase distribution board rather than a domestic unit. Beyond that, tie it into the wider electrical installation and add surge protection where sensitive equipment justifies it.

Domestic, rental or commercial

The setting changes the priorities. In a home or a refurbishment, it's about safe, modern protection and a bit of room to grow. For landlords, a compliant, well-protected consumer unit is part of keeping a property safe and inspection-ready. In commercial and industrial premises, you're usually into distribution boards, higher loads and often three-phase supplies, where getting the specification right from the start saves disruption later. In every case the same rule holds: specify with understanding, then have it installed and certified by a registered electrician.

The short version

A consumer unit distributes and protects a building's circuits; choose one with enough ways to grow into, the level of protection the installation needs (increasingly RCBO-per-circuit), a metal enclosure for domestic use, and surge protection where it earns its place. Then leave the fitting to a qualified electrician - it's notifiable work for good reason.

Browse our range of consumer units and the wider electrical and lighting range, or request a quote if you're specifying for a project or a portfolio.

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Frequently asked questions

What is a consumer unit?

A consumer unit is the enclosure that takes a building's incoming electricity supply and distributes it to separate circuits, while protecting each one. It contains a main switch to isolate everything, a busbar to carry the supply, and a row of protective devices. It's the modern equivalent of what many people still call the fuse box.

Is a consumer unit the same as a fuse box?

Effectively yes - "consumer unit" is the current term for what used to be called a fuse box or fuse board. The big difference is what's inside: modern units use switchable protective devices such as MCBs, RCDs and RCBOs rather than the old rewireable fuses.

Do I need an electrician to replace a consumer unit?

Yes. Replacing or installing a consumer unit is notifiable work under the Building Regulations and must be carried out by a competent, registered electrician who can test and certify the installation. It isn't a DIY task - you can choose and specify the unit, but the fitting belongs with a professional.

How many ways should a consumer unit have?

Enough for every circuit the installation needs, plus some spare ways so a circuit can be added later without replacing the board. The exact number depends on the property and its circuits, which your electrician will confirm - but building in a little spare capacity is always sensible.

Why are modern consumer units made of metal?

Domestic consumer units are now specified with a non-combustible enclosure - in practice, steel - to contain any fault that could otherwise cause a fire. That's why the older all-plastic boards are no longer the standard choice for new installations.