What is a
Consumer Unit?
A plain English homeowner guide to the metal box that controls every circuit in your home. What it does, the parts inside, why metal boards are now the legal standard plus when yours needs replacing.
A consumer unit (also called a fuse board or distribution board) is the main electrical control box in your home. It sits between the incoming meter supply plus every circuit in the property. It carries three jobs: switching the supply on or off, protecting against faults plus distributing power to lights, sockets, cookers, showers plus EV chargers. Modern UK consumer units are made of metal, comply with BS 7671 (the 18th Edition Wiring Regulations) plus must be installed by a Part P registered electrician.
Four figures
worth knowing
These are not preferences. They are baseline standards every modern domestic consumer unit must meet under BS 7671 plus Part P of the Building Regulations.
Typical Main Switch
The standard incoming rating on a UK domestic service. Your main switch is sized to match it plus isolates the whole property in one move.
Typical Way Count
The number of circuit positions in a domestic board. A 3-bed home typically needs 10 to 12 ways once EV plus solar are factored in.
Typical Lifespan
A modern metal board fitted to BS 7671 normally serves a property reliably for 25 to 30 years before replacement is sensible.
Notifiable Work
Installing or replacing a consumer unit is always notifiable. It must be done by a registered electrician then certified.
What is actually
inside the box
Open the front cover plus you find four components doing four jobs. Every modern UK consumer unit has all four. The way they connect changes between board styles.
Main Switch
A double-pole isolator at one end of the board. Operate it once plus the entire property is dead. The first thing you reach for when something goes wrong.
Busbar
A copper strip running across the board carrying power from the main switch to every protective device. Hidden under the front cover but the spine of the board.
RCBOs or RCDs
The protective devices for each circuit. They trip on overload, short circuit or earth fault. RCBOs cover one circuit each. RCDs cover banks of circuits.
Earthing Terminal
The main earthing terminal where the supply earth lands plus where main protective bonding to gas plus water originates. Every CPC traces back here.
A consumer unit is the brain of your home electrics
Your home gets one electrical supply from the National Grid. That supply enters the property through a meter plus the meter feeds your consumer unit. From there, the consumer unit splits the single incoming supply into separate circuits: one for upstairs lights, one for downstairs sockets, one for the cooker, one for the shower, one for an EV charger plus so on. Each of those circuits then has its own protection so a fault on one circuit does not knock out the whole house.
That is the practical job. The technical name varies: consumer unit, fuse board, distribution board, fuse box, CU. They all mean the same metal box. The terminology has changed as the technology has changed, which is why an older homeowner might still call it a fuse box even though there have not been actual rewireable fuses inside one for decades.
Where it sits in the property
In most UK homes the consumer unit is mounted close to the meter on an internal wall, usually in a hallway, cupboard, garage or downstairs WC. The meter tails (two thick insulated cables) run from the meter into the consumer unit's main switch. Beyond the main switch the supply is split out by the busbar to every circuit in the property.
The board itself is now almost always made of steel. Since the 2016 amendment to BS 7671, all domestic consumer units must have a non-combustible enclosure. That rules out the older plastic units which have been a known fire risk in real-world installs. Plastic boards are still legal where already installed. A like-for-like replacement of a plastic board with another plastic board is not compliant on a new install.
The protective devices
Inside the box, every circuit terminates at its own protective device. There are three types you will see in 2026 boards:
- MCBs (Miniature Circuit Breakers) trip on overload (too much current) or short circuit. They do not provide RCD shock protection on their own.
- RCDs (Residual Current Devices) trip on earth fault, providing shock protection at 30mA. Older boards group several circuits under one RCD.
- RCBOs (combined RCD plus MCB) give every circuit its own dedicated RCD plus MCB. This is the modern standard on full RCBO boards.
You may also see AFDDs (Arc Fault Detection Devices) on circuits feeding sleeping accommodation in newer installs, plus SPDs (Surge Protection Devices) protecting the whole installation against transient overvoltage. Both are now BS 7671 recommendations.
When it needs replacing
A consumer unit does not have a fixed expiry date. It is replaced when one of these conditions applies: the board is plastic plus failing on EICR (typically C2 coded). The board is wired in rewireable fuses or older MCB-only protection without RCDs. The board is full plus needs more circuits added (EV charger, solar, kitchen extension). Or visible damage, scorching or corrosion is present. A landlord EICR or a property sale survey is the most common trigger.
Typical replacement
cost ranges
Pricing depends on board size, RCBO vs split-load, accessibility plus whether remedial work is needed. These are typical Milton Keynes plus Bedfordshire ranges in 2026.
Consumer Unit Replacement Cost Bands
Prices include parts, labour, EIC certification plus Building Control notification. Remedial work uncovered during testing (faulty cabling, missing bonding) is quoted separately.
Four generations
of UK consumer unit
UK consumer units have evolved through four broad generations. If your board predates the late 2000s it is almost certainly worth upgrading.
Rewireable Fuses
Plastic boards with rewireable fuse wire. No RCD protection. Slow plus dangerous to operate. Almost all gone now but still found in older homes.
MCB Boards
Plastic boards with miniature circuit breakers replacing fuses. Faster operation but still no RCD shock protection on most circuits.
Dual RCD Boards
Plastic split-load boards with two main RCDs covering banks of MCBs. Major safety improvement. Still common in homes built or rewired in this window.
Metal RCBO Boards
Steel enclosure mandatory. Full RCBO protection (one device per circuit) is now the standard on new installs. AFDDs plus SPDs increasingly added.
Four facts about your
consumer unit
Know where yours is
You should be able to find your consumer unit plus operate the main switch in the dark. Take 30 seconds today to locate it plus check it is accessible.
Plastic boards still pass for now
An existing plastic consumer unit is not automatically illegal. It only fails an EICR if there is a separate safety issue. New installs must be metal.
Test the RCD twice a year
Press the test button on your RCD or RCBO every six months. It should trip instantly. If it does not, call an electrician. Do not reset plus forget.
Keep the certificate
Your Electrical Installation Certificate plus Building Control notice prove the work is compliant. You will need both for sale, EICR plus insurance claims.
Consumer Unit Upgrades in Milton Keynes
C-Lec Electrical fits new metal consumer units to BS 7671 across Milton Keynes, Bedford plus the surrounding Bedfordshire area. Free quote, certified install, EIC plus Building Control notification handled in full.
Modern metal board vs
older plastic board
If your existing board is plastic plus more than 10 years old, the case for upgrading is straightforward. The differences are not cosmetic.
Compliant 2026 standard
- ✓Steel enclosure contains internal faults. Required on every new install since 2016.
- ✓RCBO protection on each circuit means a fault only affects one circuit not half the house.
- ✓SPD plus AFDD ready with space allocated for surge plus arc fault protection.
- ✓EV plus solar ready with capacity for the modern household load profile.
- ✓25 to 30 year service life expectation when fitted to BS 7671.
Pre-2016 install
- ✗Plastic enclosure can support combustion. The reason the regulation was changed in 2016.
- ✗Single faults take out half the house on dual RCD boards. One fault, lots of circuits offline.
- ✗No SPD or AFDD provision on most older boards. Limited surge plus arc fault protection.
- ●May still pass an EICR if no separate safety issue is present. Not automatically illegal.
- ●Likely to be flagged on property sale or new tenancy regardless of EICR result.
For the wider context on RCDs, RCBOs, AFDDs plus when an upgrade is genuinely needed, head back to our full guide to consumer units where every common homeowner question is answered in one place.
Back to the Consumer Units Guide
This article sits inside our complete Consumer Units knowledge base. The hub covers everything from board types plus RCBOs through to landlord requirements plus BS 7671 wiring regulations.
More on consumer
unit basics
If you want to understand exactly how a consumer unit is wired together, our walkthrough on how to wire a consumer unit sets out the four stages a registered electrician follows on the day. To understand the older split-load boards still found in many UK homes, the explainer on what is a dual RCD board covers what they protect against plus their main weakness. For the formal wiring rules, our consumer unit wiring regulations guide breaks down the BS 7671 sections that apply. If you need a board fitted in Milton Keynes or Bedford, our consumer unit upgrades service page is the fastest route to a quote.