NEC Article 625 EV Charging — The 5 Requirements That Trip Up Installers

Requirement 1: Continuous Load Rating (625.41)

EV charging equipment is a continuous load, full stop. NEC 625.41 states that the branch circuit supplying EVSE must be rated for continuous duty.

This means:

Branch circuit conductor ampacity ≥ 125% of the maximum load (per 210.20(A))
Overcurrent device rated ≥ 125% of the maximum load
A 40A Level 2 charger needs: 40 × 1.25 = 50A circuit minimum

No exceptions, no derating. A 48A Level 2 charger (the maximum for a 60A circuit) needs a 60A breaker and 6 AWG copper conductors.

Requirement 2: GFCI Protection (625.54)

All EVSE must have ground-fault protection for personnel not exceeding 30mA per NEC 625.54. This is typically built into the EVSE unit itself (Level 2 chargers include integral GFCI), but the installer must verify:

The EVSE has listed GFCI protection, OR
An external GFCI device is installed on the branch circuit

For hardwired installations, this means the branch circuit does NOT need a separate GFCI breaker if the EVSE has integral protection. For cord-connected installations, the supply cord and plug must include GFCI.

Note: NEC 2023 moved to requiring GFCI with equipment leakage current detection (ELCI) for some configurations, providing protection against both ground faults and equipment leakage.

Requirement 3: Disconnecting Means (625.43)

A disconnecting means must be provided for the EVSE and must be:

Located within sight of the EVSE, OR
Capable of being locked in the open position (per 110.25)

"Within sight" means visible and not more than 15m (50 feet) from the equipment. For residential garage installations, the panel is often within sight. For commercial parking structures, a local disconnect switch is typically required.

The disconnecting means must simultaneously disconnect all ungrounded conductors.

Requirement 4: Ventilation for Indoor Installations (625.52)

Where EVSE is installed in indoor locations (parking garages), ventilation requirements from the mechanical code apply. NEC 625.52 references:

Mechanical ventilation must be provided per the applicable building code
Ventilation must operate when the EVSE is energised (interlocked or continuous)
Battery charging produces negligible hydrogen in modern EVs (unlike lead-acid), but the code requirement remains

Practical impact: some older parking garage ventilation systems are inadequate for the heat generated by multiple high-power chargers. The electrical designer must coordinate with the mechanical engineer on cooling load.

Requirement 5: Load Management (625.42)

NEC 2023 significantly expanded load management provisions:

Energy Management System (EMS): May be used to limit the total load from multiple EVSE units to stay within the electrical supply capacity
The EMS must be listed and must not reduce any individual EVSE below its minimum operating current
The branch circuit to each EVSE must still be rated for the EVSE's maximum current — the EMS manages the aggregate, not the individual circuit rating
Where an EMS is used, the service or feeder calculation may use the managed (reduced) load per 625.42

This allows, for example, ten 48A chargers on a 200A feeder with an EMS limiting total simultaneous charging to 200A — rather than requiring a 600A feeder for ten units.

Design compliant installations: Size EV charging circuits and load management with the EV Charging Calculator.

Frequently Asked Questions

What standards govern cable sizing calculations?

The primary standards are AS/NZS 3008.1.1:2017 (Australia/NZ), BS 7671:2018 (UK), IEC 60364-5-52 (International), and NEC Article 310 (USA). Each has different assumptions for ambient temperature, installation methods, and derating factors.

Why do different standards give different cable ratings?

Standards differ in reference ambient temperature (AS/NZS uses 40°C, BS 7671 uses 30°C), test conditions, grouping factor calculations, and installation method classifications. A 50mm² XLPE cable can vary by 15% between standards.

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