EV Charger Wire Size Calculator

NEC Article 625.42 requires EV charger (EVSE) branch circuits to be rated at 125% of the maximum charger output current — because EV charging sessions commonly last 3 or more hours, which meets the NEC definition of a continuous load (Article 100). This means the wire and breaker must be sized to 125% of the charger's rated current.

A 32A EVSE is the maximum continuous load the circuit should supply. Per NEC 125% rule: 32 × 1.25 = 40A. You need a 40A breaker and wire rated for at least 40A at 75°C (8 AWG copper or 6 AWG aluminum minimum, though voltage drop may require larger).

Most home Level-2 chargers are set to 24A, 32A, or 40A output depending on the unit. Most EVs can accept up to 48A, but most homeowners install 32A–40A circuits. A 40A EVSE (on a 50A circuit) provides about 9.6kW charging, which adds roughly 30–40 miles of range per hour for most EVs.

Yes — especially if your electrical panel is far from the garage or driveway. Voltage drop at 40A over 100+ feet can require stepping up a wire gauge. This calculator accounts for voltage drop so you get the right size for your specific run.

Aluminum conductors are permitted for circuits 6 AWG and larger. On longer runs, aluminum is commonly used for its cost advantage. You must use aluminum-rated connectors and apply anti-oxidant compound at all terminations. Always verify with your local AHJ and a licensed electrician.

In virtually all US jurisdictions, yes. A dedicated 240V branch circuit is a permitted electrical alteration. The inspector will verify the wire size, breaker rating, outlet or hardwired connection, and grounding. Do not skip the permit — it protects your home and your insurance.