NEC 625.42 Automated Load Management (ALM) & NEC 705.13 Power Control Systems for EV Fleets
Under traditional NEC Article 220 load calculations, EV chargers are classified as 125% continuous loads—meaning ten 19.2 kW chargers require 240 kW of dedicated busbar capacity. NEC 625.42 and NEC 705.13 revolutionize commercial fleet engineering by permitting AHJs to size service conductors, feeder panels, and transformers based on the maximum firmware-enforced Power Control System (PCS) setpoint rather than the sum of nameplate ratings.
Unmitigated Utility Grid vs. Solar + BESS Microgrid Architecture
| Engineering Parameter | Unmitigated Utility-Only EVSE | Solar Canopy + BESS Microgrid | Operational & Capex Advantage |
|---|---|---|---|
| NEC Feeder Sizing Basis | 125% of sum of all EVSE nameplate ratings (NEC 625.41) | 100% of maximum firmware-locked ALM / PCS current setpoint (NEC 625.42) | Allows 3x to 4x more physical charging ports on an existing 800A/1200A panelboard |
| Solar + BESS Busbar Backfeed | 120% Busbar Rule limit (NEC 705.12(B)(3)(2)) caps solar/BESS size | NEC 705.13 UL 1741 PCS dynamically monitors busbar current | Connects large solar + BESS arrays to existing switchgear without main breaker derating |
| Fail-Safe Loss of Telemetry Behavior | N/A | Hardwired CT feedback loop drops EVSE output to safe fallback amps (<2 seconds) | Guarantees main breaker never trips even if cloud internet or Wi-Fi drops |
| OCPP 2.0.1 Dynamic Solar Tracking | Static fixed amperage output regardless of solar production | Modulates charger kW every 5 seconds to match real-time PV + BESS surplus | Maximizes 100% behind-the-meter solar self-consumption |
24-Hour Depot Load Profile & 15-Minute Peak Shaving Dispatch
| Shift / Operating Window | EV Fleet Load (kW) | Solar Output (kW) | BESS Dispatch (kW) | Net Utility Meter (kW) |
|---|---|---|---|---|
| 08:00 – 12:00 (Facility Base Load + Cloud Transients) | 180 kW (Dynamically throttled by ALM) | 140 kW | +40 kW | 120 kW (Facility Base Load Only) |
| 12:00 – 15:30 (Clear-Sky Solar Surplus Ramp) | 340 kW (ALM ramps up EVSE to absorb PV) | 380 kW | -40 kW | 100 kW |
| 15:30 – 19:00 (Facility HVAC Peak + Fleet Plug-In) | 110 kW (ALM curtails non-priority chargers) | 70 kW | +190 kW | 150 kW (Strict NEC 705.13 Busbar Cap Held) |
| 19:00 – 06:00 (Nighttime HVAC Drop & Full Fleet Allocation) | 360 kW (Full panel headroom allocated to EVs) | 0 kW | 0 kW | 380 kW (Below 400 kW Service Rating) |
3-Step Commercial Engineering & Commissioning Protocol
NEC 220.87 12-Month Peak Demand Recording
Obtain 12-month utility maximum demand data (or 30-day continuous load logger recording) under NEC 220.87 to prove actual existing spare capacity on the 480V main switchboard.
UL 1741 PCS & Revenue-Grade CT Commissioning
Install Rogowski coils / split-core CTs on main service entrance conductors and solar/BESS feeders wired to a local edge controller with password-protected AHJ lockouts.
AHJ Plan Check Submittal with Code Citations
Include explicit callouts to 2023/2026 NEC 625.42(A)-(B) and NEC 705.13 on Sheet E-002 (Single-Line Diagram) showing the firmware maximum current setting.
Utility Interconnection & NEC 705.13 PCS Engineering Notice Template
Copy and customize this technical brief for your utility fleet electrification representative or AHJ electrical plan examiner.
SUBJECT: AHJ Plan Check Note — NEC 625.42 Automated Load Management & NEC 705.13 PCS Compliance Permit Application: [PERMIT_NUMBER] | Sheet Reference: E-002 Single-Line Diagram To Electrical Plan Check Examiner / AHJ Inspector: 1. Code Compliance Basis: Pursuant to 2023 NEC 625.42, where an Energy Management System (EMS) controls EVSE loads, the maximum equipment load on service and feeder conductors shall be the maximum load permitted by the automatic load management system ([ALM_MAX_AMPS] Amps @ 480V 3-Phase). 2. Busbar Protection: Pursuant to NEC 705.13, a listed UL 1741 Power Control System (PCS) monitors main busbar and feeder currents, dynamically limiting combined utility, solar PV, and BESS currents to prevent any overload of the existing [PANEL_RATING]A switchboard.
Model Your Exact Fleet Size & Utility Demand Tariff
Run custom 15-minute peak shaving numbers and export a CFO Pro-Forma PDF in our interactive calculator.
Frequently Asked Engineering & Tax Equity Questions
Can an inspector force a fleet to size the electrical panel for 100% of all chargers running at once?
Not under the 2020, 2023, or 2026 National Electrical Code if a listed Automated Load Management (ALM) / Energy Management System is installed per NEC 625.42. The code explicitly states that the feeder and service load shall be sized to the maximum amperage limit enforced by the load management controller.
What happens if the local network router or internet connection fails at the depot?
UL 1741 PCS and NEC 625.42 compliant controllers use local hardwired RS-485/Modbus or local LAN loops with a heartbeat timer. If a charger loses communication with the local controller for more than 5–10 seconds, it automatically drops to a pre-programmed fail-safe minimum current (e.g., 6A or 0A) so the breaker can never be overloaded.