How UK Home Electrics Are Laid Out

UK homes are supplied with single-phase 230V AC from the distribution network. The supply enters through a sealed meter (owned by your energy supplier) and feeds your consumer unit (CU) — typically a metal-encased box you'll find under the stairs, in a cupboard, or on a wall. Since January 2016 all new and replacement consumer units in domestic premises must have a non-combustible (metal) enclosure (BS 7671 Reg 421.1.201); older plastic units may still exist in properties wired before that date.

The Consumer Unit

MainsConsumerUnitRing main (32A)Lighting (6A)

Each MCB (Miniature Circuit Breaker) in the CU protects one circuit. If a fault occurs, the MCB trips — disconnecting only that circuit, not the whole house.

The Circuits

Most UK homes have:

  • Ring final circuit — powers all standard socket outlets (13A sockets) in a room or floor. Runs as a ring: one cable leaves the CU, loops around the sockets, and returns to the same MCB.
  • Lighting circuit — powers ceiling lights and their switches. A radial (single-run) circuit, typically protected by a 6A or 10A MCB depending on the total load.
  • Radial circuits — single-run circuits for higher-load appliances (kitchen, utility room).
⚡ Open the Design canvas to try building a circuit

What You Can Do Yourself

Under Part P of the Building Regulations, some electrical work is notifiable (requires a registered electrician or local authority approval) and some is not. As a DIYer, you can generally:

  • Add a socket or light to an existing circuit (non-notifiable)
  • Replace like-for-like fittings (non-notifiable)

You cannot do the following yourself without notification:

  • Install a new circuit from the consumer unit
  • Work in bathrooms or outdoors (all electrical work is notifiable)
  • Install new circuits in kitchens (like-for-like replacement in a kitchen is not notifiable in England since the 2013 revision of Approved Document P)

See Part P — what DIYers can & can't do for the full rules.