An automated load management system (ALMS), called an energy management system (EMS) in the National Electrical Code, is the software and controls that share a fixed amount of electrical capacity across many EV chargers, so their combined draw never exceeds what the service can supply.
Without load management, an electrical design must assume every charger draws full power at once, which can require large and expensive service upgrades. With it, the system throttles and schedules sessions, and the code allows the service to be sized to the managed maximum rather than the sum of every charger. Because most parked cars sit for hours and need only part of a full charge, the cars still leave charged.
What it can do
- Cap total charging power and divide it among active sessions.
- Prioritize vehicles by departure time, energy needed or customer type.
- Shift charging into lower-cost time-of-use periods and around building load and on-site solar. See time-of-use rate and demand charges.
- Respond to utility signals in managed-charging programs. See managed charging.
What to check
- Whether the system is listed and accepted by the local electrical inspector as an energy management system.
- How it behaves if communication is lost: it should fail to a safe, limited output.
- Whether it works across charger brands, usually through OCPP.
The Parkonomics view
Load management is how a fixed electrical service serves a growing number of chargers. Design for it from the first charger, because adding capacity later through software is far cheaper than adding it through switchgear.
Related terms: Managed Charging, Demand Charge, Make-Ready Infrastructure, kW versus kWh, OCPP
Further reading: Plugging In Wisely