EV charger cable size calculator
Work out the cable size for a home EV charger from its rated current, the length of the run and how the cable is installed. The calculator below starts with a 7.4 kW single-phase charger (32 A) on a 20 m run; change it to match yours.
Copper conductors, IEC 60364-5-52 Annex B current-carrying capacities at 30 °C, temperature factors from Table B.52.14 (rounded up to the next 5 °C step) and grouping factors for bunched circuits from Table B.52.17. The breaker is the smallest standard rating at or above the load current, and the cable must carry at least that rating after derating (Ib ≤ In ≤ Iz). Not covered here: buried cables (method D), aluminium, fault-loop disconnection times and short-circuit checks. Guidance only: check the standard, the cable maker's data and your national wiring rules. The installer remains responsible for the design.
Typical sizes for home chargers
Copper PVC cable at 30 °C, not grouped with other circuits, sized for a 3% voltage drop on the charger circuit. The breaker equals the charger's rated current.
| Charger | Installation | 15 m | 30 m | 50 m |
|---|---|---|---|---|
| 7.4 kW (32 A, 1-phase 230 V) | C (clipped direct) | 4 mm² | 10 mm² | 16 mm² |
| 7.4 kW (32 A, 1-phase 230 V) | A1 (insulated wall) | 6 mm² | 10 mm² | 16 mm² |
| 11 kW (16 A, 3-phase 400 V) | C (clipped direct) | 1.5 mm² | 2.5 mm² | 4 mm² |
| 11 kW (16 A, 3-phase 400 V) | A1 (insulated wall) | 2.5 mm² | 2.5 mm² | 4 mm² |
| 22 kW (32 A, 3-phase 400 V) | C (clipped direct) | 4 mm² | 4 mm² | 6 mm² |
| 22 kW (32 A, 3-phase 400 V) | A1 (insulated wall) | 10 mm² | 10 mm² | 10 mm² |
Why the rated current, not the power
A charger draws its full rated current for hours at a time, so IEC 60364-7-722 treats it as a continuous load: size the circuit for the charger's rated current, with no diversity. A 7.4 kW charger is a 32 A load. If the charger lets you set a lower current (for example 16 A), size the cable for the setting you will actually use, and remember it may be raised later.
Also check
- A dedicated circuit for each charging point.
- RCD protection. Each charging point needs its own RCD, and the charger or the RCD must handle DC fault current (often a type A RCD plus 6 mA DC detection in the charger, or a type B RCD). The charger's installation manual says which.
- Outdoor and buried runs. Buried cables (method D) and cables in direct sun need other factors than this calculator covers.
- Your supply. The main fuse and the rest of the house load must have room for the charger. Many chargers can limit their current to protect the main fuse.
Questions
What size cable do I need for a 7 kW EV charger?
A 7.4 kW charger draws 32 A on 230 V. Clipped direct over 15 m that is 4 mm², and at 30 m the voltage drop pushes it to 10 mm² (3% limit). Run through an insulated wall it needs 6 mm² even on a short run. Check your own length and installation in the calculator above.
What size cable for an 11 kW charger?
11 kW is 16 A per phase on 400 V three-phase. Clipped direct it needs 1.5 mm² at 15 m and 4 mm² at 50 m.
What size cable for a 22 kW charger?
22 kW is 32 A per phase on 400 V three-phase. Clipped direct it needs 4 mm² at 15 m and 6 mm² at 50 m; in an insulated wall 10 mm² at 15 m.
Can I rely on the result without checking?
No. It is guidance based on IEC 60364. Follow the charger's installation manual and your national wiring rules, which may add requirements. The installer remains responsible for the design.
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