EVSE Circuit Sizing Quick Reference (NEC 625.42)
| EVSE Output | Circuit Breaker (125% rule) |
Min. Copper AWG | Min. Aluminum AWG | Outlet Type | Calculate VD |
|---|---|---|---|---|---|
| 16A (Level 2 basic) | 20A | #12 AWG (25A) | #10 AWG (30A) | NEMA 6-20 or hardwired | Calculate |
| 24A | 30A | #10 AWG (35A) | #8 AWG (40A) | NEMA 6-30 or hardwired | Calculate |
| 32A | 40A | #8 AWG (50A) | #6 AWG (50A) | NEMA 14-50 or hardwired | Calculate |
| 40A | 50A | #6 AWG (65A) | #4 AWG (65A) | NEMA 14-50 or hardwired | Calculate |
| 48A (most common max) | 60A | #6 AWG (65A) | #4 AWG (65A) | Hardwired | Calculate |
| 80A (commercial/fast) | 100A | #1/0 AWG (150A) | #3/0 AWG (155A) | Hardwired | Calculate |
Circuit breaker per NEC 240.6(A) standard sizes. Wire ampacity at 75°C per NEC Table 310.15(B)(16). Continuous load factor per NEC 625.42. Always verify with EVSE manufacturer specifications before installation.
NEC 625.42 — The Continuous Load Rule for EV Chargers
NEC 625.42 classifies EV charging equipment as a continuous load — a load expected to remain on for three or more continuous hours. Under NEC 210.20(A), circuits supplying continuous loads must have the breaker and conductors sized at 125% of the continuous load current.
This means a 48A EVSE requires a 60A circuit (48 × 1.25 = 60A), and the supply conductors must have at minimum 60A of ampacity at the applicable temperature column. The 60A breaker protects the circuit, and the conductors are sized to carry 60A safely.
Common Residential EV Charger Setups
- 32A EVSE (Tesla Wall Connector, ChargePoint, etc.) → 40A circuit: #8 AWG copper, 40A double-pole breaker. Most common residential installation. Delivers about 25 miles of range per hour of charging on most EVs.
- 48A EVSE → 60A circuit: #6 AWG copper, 60A double-pole breaker. Maximum for many US residential panels without service upgrade. Delivers about 37 miles per hour for most EVs.
- NEMA 14-50 outlet → 40A EVSE: Installing a NEMA 14-50 outlet lets you use a portable EVSE. The outlet requires a 50A circuit and #6 AWG copper, but limits the EVSE to 40A output per NEC 625.42.
Voltage Drop for EV Charger Circuits
Garage EV charger circuits are often 50–100 feet from the main panel. At 48A (on a 60A circuit), #6 AWG copper maintains NEC 3% voltage drop to about 38 feet. For longer garage runs or subpanel installations, upsize to #4 AWG copper (60 feet) or #2 AWG copper (94 feet) at 48A/240V. Use the calculator links in the table above to check your specific run length.
Frequently Asked Questions
It depends on the EVSE output rating. Per NEC 625.42 (125% continuous load): 32A EVSE → 40A circuit / #8 AWG copper; 40A EVSE → 50A circuit / #6 AWG copper; 48A EVSE → 60A circuit / #6 AWG copper. See the table above for all common sizes.
NEC 625.42 classifies EV chargers as continuous loads. Under NEC 210.20(A), the circuit breaker and conductors must be sized at 125% of the EVSE output current. A 48A charger therefore requires a 60A circuit.
48A × 125% = 60A. Use a 60A double-pole breaker with #6 AWG copper or #4 AWG aluminum conductors (both rated 65A at 75°C).
No. A 32A EVSE needs a 40A circuit. #10 AWG copper (35A at 75°C) is insufficient — use #8 AWG copper (50A rated) for a 32A EVSE on a 40A circuit.
The Tesla Wall Connector is configurable. Most homeowners set it to 48A, requiring a 60A circuit with #6 AWG copper. At 40A output (a 50A circuit), #6 AWG copper or #4 AWG aluminum is correct.
Yes. Level 2 chargers operate on 240V single-phase (or 208V commercial). They require a dedicated 2-pole breaker, 4-wire 240V circuit (two hots, neutral, ground), and a proper EVSE outlet or hardwired connection.