EV Charger Cable & Breaker Size Calculator
Get the right electrical spec for your wallbox: cable cross-section, breaker rating and voltage drop, based on power, voltage and distance.
Breaker rating
Cable cross-section
Current draw
Voltage drop
Recommended specs by charger size
| Charger | Current | Breaker | Cable (10-25 m) |
|---|---|---|---|
| 3.7 kW 1-phase | 16 A | 20 A | 2.5-4 mm² |
| 7.4 kW 1-phase | 32 A | 40 A | 6-10 mm² |
| 11 kW 3-phase | 16 A/phase | 20 A | 4-6 mm² |
| 22 kW 3-phase | 32 A/phase | 40 A | 10 mm² |
These are planning guides only — have a qualified electrician size and install your circuit. Local codes may require different ratings.
Frequently asked questions
What size cable do I need for an EV charger?
For a 7.4 kW charger at 230V you need roughly 6-10 mm² copper over typical runs. Longer runs need thicker cable to avoid voltage drop. Always consult an electrician.
What breaker size do I need?
A 7.4 kW single-phase charger needs a 32A breaker; 11 kW three-phase needs 16A per phase; 3.7 kW needs 16A. Size up for continuous loads (chargers run for hours).
Can I install a 22 kW charger on a standard panel?
Rarely — 22 kW three-phase demands significant service capacity and often a panel upgrade. Most homes install 7.4 or 11 kW without changing the main service.
Why do EV chargers need special breakers?
Chargers run at continuous full load for hours, which heats circuits. Breakers must be rated for continuous duty (typically 125% of load), and circuits need proper grounding.