How many ways does a standard UK house consumer unit need?

Most three-bedroom homes are properly served by a 10 to 12-way board. That covers upstairs and downstairs lighting, upstairs and downstairs sockets, kitchen ring, cooker, shower, smoke alarms and immersion, with two or three spare ways for future circuits.

What does 'way' mean on a consumer unit?

A way is a single module position on the busbar, each taking one protective device. An RCBO occupies one way and protects one circuit. A main switch and any surge protection device also occupy ways, so a '10-way' board does not give you 10 usable circuits.

Do I need RCBOs or an RCD split-load board?

RCBOs are now the default choice. Each circuit has its own combined RCD and MCB, so a fault on one circuit does not take out half the house. Split-load boards with shared RCDs are cheaper but a single earth fault can disconnect several circuits at once.

Does a new consumer unit have to be metal?

Yes, for domestic premises. Since Amendment 3 to BS 7671 in 2016, consumer units in domestic installations must have a non-combustible enclosure or be housed in one — in practice this means a steel enclosure.

Do I need surge protection?

BS 7671 requires an assessment of the risk. In practice a Type 2 SPD is fitted in most new domestic boards, and it is strongly recommended where the property has significant electronic equipment, solar PV, an EV charger or a heat pump. It occupies one or two ways.

Consumer Units

What size consumer unit do I need?

By Steve Green · Updated 6 August 2026 · 6 min read

Most UK three-bedroom homes need a 10 to 12-way consumer unit populated with RCBOs. Count one way per circuit, add one for the main switch, one or two for a surge protection device, and leave at least two spare ways for future circuits such as an EV charger, heat pump or garden supply. Flats often manage on 8 ways; large or extended houses commonly need 16 to 18.

Step 1: count your circuits

A typical modern house has more circuits than people expect. Tick off the ones that apply:

Downstairs lighting
Upstairs lighting
Downstairs sockets (ring or radials)
Upstairs sockets
Kitchen sockets — usually a dedicated circuit
Cooker / hob
Electric shower
Immersion heater
Boiler or heating controls
Smoke and heat alarms
Outside sockets or garden lighting
Garage, shed or outbuilding supply
EV charge point
Solar PV / battery / heat pump

Step 2: add the non-circuit ways

Item	Ways used
Main switch (100A DP)	2 on most ranges
Type 2 surge protection device	1–2
Each RCBO-protected circuit	1
Recommended spare capacity	2+

This is the point people get caught out. A "10-way" board with a main switch and an SPD leaves roughly seven usable circuits — not ten.

Quick sizing by property

Property	Typical circuits	Recommended board
1-bed flat	5–6	8-way
2-bed flat / small terrace	6–8	10-way
3-bed semi	8–10	12-way
4-bed detached	10–13	16-way
Extended / annexe / home office	13–16	18-way or split boards

Step 3: plan for what's coming

The single most common reason we return to a board within five years is an EV charger installation. A charge point needs its own way, and load management or a heat pump will want another. Specifying two spare ways at the outset costs very little compared with replacing the board again later.

RCBOs versus split-load boards

A split-load board shares one RCD across several circuits, so a fault on the fridge can also kill the lighting. An all-RCBO board isolates faults to the single affected circuit. For anyone working from home or with a freezer, the discrimination is worth the difference in price. All-RCBO boards also make fault finding considerably faster.

Also check the incoming supply

Board size is only half the picture. The main fuse (usually 60A, 80A or 100A), earthing arrangement (TN-S, TN-C-S or TT) and main protective bonding all have to be right before a new board is energised. If bonding to gas and water is undersized, it must be upgraded as part of the work — a legitimate cost, not an upsell.

Not sure whether you need a new board at all? Read fuse board vs consumer unit, or see our consumer unit replacement service for what is included and what it costs.

Frequently asked

How many ways does a standard UK house consumer unit need?: Most three-bedroom homes are properly served by a 10 to 12-way board. That covers upstairs and downstairs lighting, upstairs and downstairs sockets, kitchen ring, cooker, shower, smoke alarms and immersion, with two or three spare ways for future circuits.
What does 'way' mean on a consumer unit?: A way is a single module position on the busbar, each taking one protective device. An RCBO occupies one way and protects one circuit. A main switch and any surge protection device also occupy ways, so a '10-way' board does not give you 10 usable circuits.
Do I need RCBOs or an RCD split-load board?: RCBOs are now the default choice. Each circuit has its own combined RCD and MCB, so a fault on one circuit does not take out half the house. Split-load boards with shared RCDs are cheaper but a single earth fault can disconnect several circuits at once.
Does a new consumer unit have to be metal?: Yes, for domestic premises. Since Amendment 3 to BS 7671 in 2016, consumer units in domestic installations must have a non-combustible enclosure or be housed in one — in practice this means a steel enclosure.
Do I need surge protection?: BS 7671 requires an assessment of the risk. In practice a Type 2 SPD is fitted in most new domestic boards, and it is strongly recommended where the property has significant electronic equipment, solar PV, an EV charger or a heat pump. It occupies one or two ways.

Need a straight answer about your own property?

Call 0203 576 6961 — answered by a real person, available 24/7 — or request a free written quote.