EV Charger Circuit Calculator — Breaker, Wire & Range/hr
Planning a Level 2 EV charger at home? Pick your charger's amperage and this calculator shows the required breaker size (NEC 125% continuous-load rule), minimum copper wire gauge, estimated miles of range per hour of charging, and whether a NEMA 14-50 outlet or a hardwired connection is required.
Why the breaker is bigger than the charger
EV charging is a textbook continuous load — it can run for 3+ hours at full current. NEC 625.42 therefore requires the circuit to be rated at 125% of the charger's output: a 48 A charger needs a 60 A breaker and 6 AWG copper, not a 50 A circuit. Plug-in installations top out at 40 A on a 50 A circuit because NEMA 14-50 receptacles and plugs are only rated for 40 A continuous; anything faster must be hardwired.
Range-per-hour assumes ~3.5 miles per kWh (typical modern EV). Your vehicle's onboard charger may cap AC intake below the station's rating — a car limited to 7.7 kW won't charge faster on a 19.2 kW unit. 80 A installations frequently require a panel or service upgrade. Wire sizes assume copper 75°C conductors; long runs over ~100 ft should be upsized for voltage drop. Always have EV circuits installed by a licensed electrician.