EV charger ratings and load management
EV chargers must be rated for the load they serve. The service and feeder may be sized to a lower, managed load when an energy management system or a restricted-access adjustable setting limits the chargers.
What the code requires
EV charging equipment must have a rating that suits the load it serves, and the code treats EV charging as a continuous load. Normally the service and feeder are sized to the full ratings of the chargers. Section 625.42 gives two ways to size for less.
Energy management system, 625.42(A): when an energy management system (EMS) that complies with 750.30 controls the chargers, the service and feeder load is the maximum the EMS allows. The EMS can be built into one unit or be part of a listed multi-unit system, and equipment with built-in load management must be marked. People often say EVEMS, but the 2023 NEC uses the term EMS.
Adjustable settings, 625.42(B): a charger with an adjustable current setting may be rated at the adjusted value when access to the adjustment is restricted under 750.30(C). The adjusted rating goes on a durable rating label on the equipment.
For the load calculation under 220.70, the EMS's maximum setpoint may be used as a single continuous value.
On the job
- When a charger is turned down to fit an existing panel, check that its label shows the adjusted rating and that the circuit is sized from that rating under 625.41.
- Your inspector will want to see how access to the setting is restricted, as 750.30(C) requires.
- An EMS lets several chargers share a service or feeder sized to the managed load instead of the full charger ratings.
What changed in 2023
The 2023 edition split the old single paragraph on automatic load management into (A) energy management systems and (B) adjustable settings, and moved the access-restriction rules to 750.30(C).
Related sections
- NEC 625.40: Dedicated circuits for EV chargers
- NEC 625.41
- NEC 750.30
- NEC 220.57
- NEC 220.70
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