EV Load-Management (EVEMS) Diversified Load (NEC 625.42)
The diversified service load of a bank of EV chargers under a NEC 625.42(A) energy management system.
Example
You enter
- Number of EVSE (chargers) 4
- Per-charger continuous rating (A) 40
- EVEMS aggregate limit (A, 0 = no management) 80
- Apply the 2026 125% factor to the setpoint? true
You get
- Un-managed sum (125% of all) 200 A
- Managed demand 100
- Freed headroom 100
Checked against published worked examples from: NEC 2023 625.42(A) / 2026 625.48.
Details, formula, and sources
ScopeWithout an EVEMS the service carries the SUM of every charger at 125% (forcing an upgrade); with a listed EVEMS the demand is 125% of the aggregate limit it enforces, not the sum. Four 40 A chargers held to 80 A: 200 A sum vs 100 A managed -- 100 A freed, so four chargers land on the capacity of two.
Formula or tableunmanaged_sum = 1.25 x per_charger x count; managed_demand = evems_limit > 0 ? (setpoint125 ? 1.25 : 1.0) x evems_limit : unmanaged_sum; freed_headroom = unmanaged_sum - managed_demand.
Source and editionNEC 2023 (NFPA 70). Article 625 (625.42(A) energy management systems) with the 2026 625.48 continuous factor on the EVEMS setpoint.
Free accessFree read-only access at nfpa.org/freeaccess.
What governsEstimate. AHJ and licensed electrician govern. Verify against the NEC edition adopted in your jurisdiction.
API field namescharger_count, per_charger_a, evems_limit_a, apply_125_setpoint, unmanaged_sum_a, managed_demand_a, freed_headroom_a
- Diversified demand with a listed EVEMS the demand is the aggregate limit it enforces, not the sum of all chargers at 125%NEC 2023 625.42(A)
- 2026 setpoint factor the 2026 NEC (625.48) applies the 125% continuous factor to the EVEMS setpoint; the EVEMS must be listed and enforced in hardwareNEC 2026 625.48; the AHJ governs