A Level 2 EV charger runs at a continuous load for hours, so the NEC treats it as continuous and requires extra capacity. This guide walks through the breaker, wire and panel checks for a typical home installation.
The 125% rule
Under NEC 625.41 and 210.19(A)(1), the circuit rating must be at least 125% of the charger's rated current. The common pairings are:
- 32 A charger: 40 A breaker
- 40 A charger: 50 A breaker
- 48 A charger: 60 A breaker
Choosing the wire
With 75°C terminals, copper THHN in conduit needs 8 AWG for a 40 or 50 A breaker (50 A at 75°C) and 6 AWG for 60 A (65 A at 75°C). If you use NM-B cable, the 60°C column applies, so a 50 A circuit needs 6 AWG (55 A) and a 60 A circuit needs 4 AWG (70 A). Long runs may need a larger size to keep voltage drop near 3%.
Check the panel
Add the charger's 125% value to the home's existing calculated load (Article 220 or measured demand) and compare it with the service rating. Example: a 200 A service with a 120 A calculated load has 80 A available, so a 48 A charger needing 60 A fits with 20 A left.
Load management
If the panel is too full, an energy management system under NEC 625.42 can limit the charger's draw automatically, allowing a smaller breaker or a bigger charger on the same service. CEC Rule 8-106(11) offers a similar approach in Canada.
Other practical points
- Hardwired chargers avoid receptacle heat issues; if you use a receptacle, choose a rated, high-quality one.
- Permits and inspection are required in most jurisdictions.
- Have a licensed electrician confirm the load calculation, especially on older panels.
Try the calculators
For informational and educational purposes only. Always consult a licensed electrician and local code authority. See our Electrical & Legal Disclaimer. Found an error? Tell us.