EV Charger Circuit Calculator

Size the circuit breaker, wire gauge, and estimate installation cost for a home Level 2 EV charger.

Results

Visualization

How It Works

EV charging is a continuous load under the NEC, meaning the circuit must be sized at 125% of the charger amperage. A 40A charger needs a 50A breaker, not a 40A. Wire gauge depends on the breaker size and the distance from the panel to the charger.

The Formula

Breaker = Charger Amps x 1.25 (round up to standard size). Wire sized per NEC 310.16 ampacity table.

Variables

  • Charger Amps — Maximum continuous current draw of the EV charger
  • 1.25 — NEC continuous load multiplier (125%)
  • AWG — American Wire Gauge -- smaller number means thicker wire
  • Run Length — Distance from electrical panel to charger location

Example

A 40A hardwired charger on 240V: breaker = 40 x 1.25 = 50A. Wire = 6 AWG copper for runs up to 100 ft. Daily capacity = 40A x 240V / 1000 x 8 hrs = 76.8 kWh -- enough for about 250 miles of range.

Tips

  • A 48A charger is the fastest Level 2 option and adds about 37 miles of range per hour on most EVs.
  • NEMA 14-50 outlets are convenient because the charger can be unplugged and taken with you when you move.
  • Hardwired installations look cleaner and may allow higher amperage than a plug-in setup.
  • Check if your utility offers an EV time-of-use rate -- charging overnight can cut costs by 50% or more.
  • Make sure your main panel has enough capacity for the new circuit before starting the installation.