The accepted standard for electrical wiring in the UK is the IEE wiring regulations, formally known as BS 7671 :2001 and colloquially referred to as "the regs". For most practical purposes, these regulations have the force of law and must be adhered to for all new electrical installations or when altering an existing system.

The standard nominal supply voltage in domestic installations is 230V AC at 50Hz, single-phase. This voltage was chosen as the harmonised standard across Europe but in practice the supply voltage in the UK remains at 240V which is within the required tolerance of 230V +10%/-6%. Commercial and industrial premises may be supplied with three-phase star-wired (US: wye) power at nominal 400V (actual 415V) phase to phase.

The standard wiring colours in appliance flexes are earth - green/yellow striped; live - brown; neutral - blue.

The standard colours in fixed wiring are currently changing to harmonise with other European countries. For a transitional period (April 2004 - April 2006) either set of colours may be used, provided that any changes in the colour scheme are clearly labelled. From April 2006, only the new colours may be used in new wiring.

The colour changes have been controversial, because the colour blue which was previously used as a phase colour is now the colour for a neutral conductor, and the colour black which was previously used for neutral is now a phase colour. Any confusion between these conductors could be very dangerous. Additionally, it has been suggested that it will be more difficult to differentiate between the new phase colours particularly in low-light conditions.

British wiring has some unusual features such as the ring circuit.