What Size Wire for a 32 Amp EV Charger?

A 32A EV charger needs #8 copper or #8 aluminum conductors on 75°C-marked terminations (#8 copper or #6 aluminum at 60°C or on NM-B cable) on a 40A breaker. EV charging is a continuous load, so the circuit is sized at 125% of the charger's output (32 × 1.25 = 40A, rounded up to a 40A standard breaker per NEC 625.41 and 210.20(A)). The wire is sized at the 75°C column of NEC Table 310.16, which on a circuit of 100A or less holds only where the breaker and the charger are both listed and marked for 75°C conductors (NEC 110.14(C)(1)(a)). The equipment grounding conductor is #10 copper per NEC Table 250.122. These sizes are at 86 F ambient with 1-3 current-carrying conductors, which is the basis the ampacity tables are printed at. A hotter run, or more current-carrying conductors sharing the raceway, derates the conductor under NEC 310.15(B)(1) and NEC Table 310.15(C)(1) and can call for a larger one. The Intry EV charger calculator sizes for the conditions you enter. On 60°C terminations, or if the run uses NM-B cable (Romex), the 60°C column applies (NEC 110.14(C)(1)(a), 334.80), so use #8 copper instead.

A 40A double-pole breaker. Because EVSE is a continuous load, NEC 625.41 requires the overcurrent device to be rated at least 125% of the charger's output: 32 × 1.25 = 40A, and the next standard breaker size is 40A.

Yes. A 32A Level 2 charger, whether hardwired or plug-in, must be on its own dedicated branch circuit that serves no other load (NEC 625.40). NEC 625.40's own Exception permits one branch circuit to feed multiple EVSEs where 625.42(A) or (B) allows it; it does not permit an EVSE to share a circuit with an ordinary appliance. A plug-in unit on a NEMA receptacle also needs GFCI protection at the breaker (NEC 625.54); most hardwired units have built-in CCID/GFCI and do not.

#8 Cu carries a 40A circuit at ampacity, but on long runs voltage drop, not ampacity, sets the limit. Past roughly 100 feet you may need to upsize one gauge to stay within the 3% drop recommendation. Enter your exact distance in the calculator below to check.