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EV Charging Demand Load

NEC 625.42 · EVSE Demand Load & Service Impact

When to use: Sizing the service or feeder impact of EV charging equipment. Per NEC 625.42 EVSE is a continuous load, so conductors and overcurrent protection are sized at 125% of the rated current. An energy management system or load calculation may permit a diversity / demand factor below 100% to reduce the connected load. Use this to assess whether an existing service can absorb the new EVSE load.

EVSE Parameters

Number of EVSE Chargers

Power per Charger

Diversity / Demand Factor100 = none

Existing Service Load

Service Voltage

Service Phase

Calculation Steps

Connected = 6 × 11.5 = 69.00 kW

Demand = 69.00 × 100% = 69.00 kW

I = (69.00 × 1000) / 240 = 287.5 A

Continuous = 287.5 × 1.25 = 359.4 A

Demand Current

287.5A

Continuous sizing × 1.25 = 359.4 A

Results

Connected Load69.00 kW

Demand Load69.00 kW

Demand Current287.5 A

Continuous Sizing (×1.25)359.4 A

Total Service Load109.00 kW

Diversity Factor100 %

NEC References

NEC 625.42 — EVSE load calculation

EVSE is a continuous load (×1.25)

Energy management permits diversity

NEC 220 — Service/feeder demand