What Size Cable
for an EV Charger?

What size cable a UK EV charger actually needs

Cable sizing for UK EV chargers follows BS 7671 (the IET Wiring Regulations) which specify how cable cross-section relates to current capacity, run length and install method. The cable must handle the EV charger's continuous load (32A for typical 7kW installs) without exceeding safe temperature limits. Get the sizing wrong and the cable can overheat which damages the insulation and creates fire risk.

Standard UK home EV charger sizing

For a typical 7kW (32A) home EV charger with cable run under 15 metres in standard install conditions (cable clipped to wall surface or run through standard chase), 6mm² twin-and-earth (6242Y or similar) is the standard answer. This size handles 32A continuous load comfortably with appropriate margin for UK environmental conditions.

When you need 10mm² instead

Several scenarios require stepping up to 10mm². Cable run over 15 metres adds resistance which causes voltage drop. 10mm² maintains the voltage at the charger end. Buried armoured cable (SWA) for runs through gardens or detached outbuildings adds insulation that reduces heat dissipation, requiring larger cable to compensate. Cable runs through hot environments (loft spaces in summer, near boilers) reduce capacity and may need upsize. Multiple cables in the same conduit derate each other.

The installer calculates these factors during the site survey using the BS 7671 derating tables. Most UK 7kW home installs end up at 6mm² or 10mm² depending on the specific situation. Larger sizes (16mm² or 25mm²) are rare in domestic settings and usually indicate three-phase or commercial installations.

What about the charging cable itself

The cable from the charger to your EV (Type 2 cable) is sized differently because it is rated as part of the charging assembly. UK Type 2 cables for 7kW use are typically 6mm² conductors with appropriate insulation. 11kW and 22kW Type 2 cables use larger conductors. The cable rating is marked on the cable itself and matched to the charger maximum output. This is a portable equipment specification, not the building wiring specification.

Three-phase considerations

Three-phase UK installations (rare in domestic, more common in commercial) need different cable sizing because the load is balanced across three phases. A 22kW three-phase install pulls only around 32A per phase rather than 96A on single phase. Cable size is similar to single-phase 7kW installs (typically 6mm² per conductor) but requires four-core SWA cable rather than twin-and-earth. Three-phase installs always use Part P registered electricians familiar with the requirements.