EV chargers are one of the highest-draw appliances in a home. A Level 2 charger on a 50A circuit draws more power than most other household appliances. Proper wire sizing is critical for safety and charging speed.
Level 1 (120V, 12A): Uses a standard 20A outlet — 12 AWG on existing circuit. Level 2 (240V, 30-50A): Dedicated circuit required — 10 AWG for 30A, 8 AWG for 40A, 6 AWG for 50A. Level 2 (240V, 60-80A): For Tesla Wall Connector or high-power units — 4 AWG for 60A, 3 AWG for 80A.
NEC Article 625 requires that EV charger circuits be sized at 125% of the continuous load. A 40A charger needs a 50A breaker and wire rated for 50A. This means 6 AWG copper (rated 65A at 75°C). The charger must be on a dedicated circuit — no other loads on the same breaker.
Many EV chargers are installed in detached garages, requiring long wire runs. For a 50-foot run at 40A (240V), 6 AWG copper has about 1.1% voltage drop — well within limits. For 100+ foot runs, consider upsizing to 4 AWG to keep voltage drop under 3%.
If budget allows, install a 60A circuit even if your current charger only needs 40A. EV battery sizes keep growing, and faster Level 2 chargers are becoming common. Running 6 AWG or 4 AWG now avoids having to re-wire later. Also consider installing conduit rather than direct wiring, which allows future upgrades without opening walls.
Disclaimer: This guide is for informational purposes only. Always consult a licensed electrician and follow local building codes for actual installations. Wire sizing depends on specific conditions including ambient temperature, conduit fill, and derating factors.