This article discusses NEC 2023 or 2026. ZinaVee's calculators use NEC 2017.
Published: June 2026 Technical Level: Advanced Category: Power Systems Design
EV charging infrastructure design requires the engineer to address three distinct engineering problems simultaneously: the NEC 2023 Article 625 installation requirements that govern the EVSE equipment itself, the service entrance and feeder sizing that must accommodate both the EVSE load and the existing facility load, and the grid impact assessment that determines whether the local distribution transformer and feeder can support the additional demand without requiring utility infrastructure upgrades. NFPA 70 Articles 210, 220, and 625 together establish the wiring method, load calculation, and EVSE installation requirements; IEEE Standard 2030.1.1 and the SAE J-series standards govern the connector and communication interfaces; and NEC Section 625.42 provides the load management system provisions that allow demand-managed EVSE to be designed for reduced service entrance capacity. This paper addresses all three engineering problems in the sequence that a practicing engineer would encounter them in a commercial EVSE project.
NEC 2023 Article 100 and Article 625 classify EVSE by output type and power level. Level 1 EVSE operates at 120 V AC, 15 or 20 A, providing 1.4 to 1.9 kW of charging power. Level 2 EVSE operates at 240 V AC single-phase or 208 V three-phase, 15 to 80 A, providing 3.3 to 19.2 kW. DC Fast Charging EVSE (Level 3) provides DC output at 200 to 1,000 V DC, up to 350 kW, with the AC-DC conversion performed within the EVSE rather than the vehicle's on-board charger.
NEC Section 625.40 requires that each EVSE be supplied by a dedicated branch circuit or individual circuit. NEC Section 625.41 establishes the minimum branch circuit rating: the branch circuit must be rated at not less than 125 percent of the EVSE's maximum load, consistent with NEC Section 210.20's continuous load rule. A 19.2 kW Level 2 EVSE on a 208 V three-phase circuit draws A; the branch circuit must be rated at least A, requiring a 70 A circuit.
The service entrance load calculation for a facility with EV charging follows NEC Article 220, with the EVSE loads calculated per NEC Section 625.42. For uncontrolled EVSE (no energy management system), the full nameplate load of all EVSE is included in the service entrance calculation at 100 percent. For EMS-controlled EVSE per Section 625.42(B), the load is calculated as the maximum simultaneously permitted output of the EMS.
The feeder from the service entrance to the EVSE distribution panel must be sized for the total EVSE load at 125 percent (continuous load rule) plus any existing loads on the same feeder. A 100 A EVSE distribution panel serving five 7.2 kW Level 2 EVSE (36 kW total, uncontrolled) requires a feeder rated at A minimum, so a 150 A feeder circuit is appropriate.
Large EVSE installations may require coordination with the serving utility before construction. Utilities typically require notification for EVSE installations that add more than 50 kW of new demand at a service point, and they may require a service upgrade or transformer replacement before the EVSE can be energized. The notification requirement varies by utility tariff; the engineer should confirm the applicable threshold with the serving utility during the preliminary design phase to identify whether a utility upgrade is on the critical path and to include the utility upgrade timeline in the project schedule.
For installations that trigger a utility transformer upgrade, the upgrade cost may be allocated to the customer, the utility, or shared depending on the utility's tariff structure and the regulatory framework in the applicable state. This cost should be identified in the preliminary budget estimate and escalated to the project owner for financial planning.
[1] NFPA 70, National Electrical Code, Articles 210, 220, 625, 2023 edition, NFPA, 2023.
[2] SAE J1772, SAE Electric Vehicle and Plug-in Hybrid Electric Vehicle Conductive Charge Coupler, SAE, 2017.
[3] SAE J3400, NACS Electric Vehicle Coupler, SAE, 2023.
[4] IEEE Standard 2030.1.1-2021, Standard Technical Specifications of a DC Quick and Bi-directional Charger, IEEE, 2021.
[5] IEC 61851-1:2017, Electric Vehicle Conductive Charging System: General Requirements, IEC, 2017.
[6] EPRI, Electric Vehicle Supply Equipment (EVSE) Installation Guide, EPRI Technical Report, 2022.
[7] UL 2594, Standard for Electric Vehicle Supply Equipment, UL, 2021.
[8] NREL, Charging Infrastructure Deployment and Grid Integration, NREL/TP-5400-74198, 2019.