Energy throttling logic is the set of rules and control algorithms that intentionally reduce EV charging power (kW) or limit energy delivery under certain conditions. The goal is to keep the site within electrical constraints, reduce costs, protect equipment, and maintain stable operation—while still delivering the required energy to vehicles as efficiently as possible.
What Is Energy Throttling Logic?
The energy throttling logic determines when throttling should occur, how much power to reduce, and which chargers or vehicles to prioritize.
– Enforces a site-wide import limit (grid connection or transformer capacity)
– Prevents breaker trips by staying under feeder and distribution board limits
– Manages simultaneous charging sessions across many connectors
– Protects equipment from overheating or abnormal operating conditions
– Supports tariff strategies (avoid peak periods, demand charge windows)
Throttling can be applied dynamically in real time and adjusted continuously based on measured load.
Why Energy Throttling Matters for EV Charging
Without controlled throttling, multi-charger sites can overload quickly.
– Avoids nuisance trips and downtime caused by electrical overloads
– Enables more chargers on the same connection using controlled power sharing
– Reduces peak demand and exposure to demand charges
– Helps fleets meet “energy by departure” targets without exceeding site limits
– Improves stability of charging sessions and reduces aborted sessions due to power events
How Energy Throttling Logic Works
A typical control loop uses measurement, decision, and command.
– Measure: site load, charger demand, and available headroom (kW)
– Decide: allocate power across chargers based on priorities and constraints
– Command: set charging limits per charger/connector (often via OCPP or local controller)
– Validate: confirm delivered power matches limits and adjust if conditions change
Throttling can be local (charger-level) or centralized (site controller/EMS coordinating many chargers).
Common Triggers for Throttling
– Site import approaches a contractual or technical limit (e.g., transformer rating)
– Peak-demand windows where costs are highest
– PV output drops and onsite supply is no longer available
– BESS reserve threshold reached (battery must stop supporting load)
– Thermal limits inside a charger or cabinet (temperature protection)
– Power quality events or abnormal grid conditions
– Emergency operating modes (reduced power to keep essential vehicles charging)
Common Throttling Strategies
Fair-share throttling
– Split available power evenly across active sessions
– Works well for employee and destination charging where “fairness” matters
Priority-based throttling
– Prioritize specific vehicles/users (fleet readiness, emergency vehicles, VIP bays)
– Allocate remaining power to others
Energy-by-departure throttling
– Allocate power based on required kWh and departure time
– Minimizes wasted peak demand while meeting operational targets
Price-aware throttling
– Reduce charging during expensive tariff periods; increase during cheaper periods
– Often paired with scheduling and energy arbitrage if storage is available
DER-aware throttling
– Increase charging when PV is abundant; reduce when PV drops
– Coordinate with BESS dispatch and import/export rules
Key Inputs to Throttling Logic
– Real-time site metering (import kW, feeder loads)
– Charger status and requested power (active sessions, connector states)
– Vehicle constraints (max acceptance, single/three-phase limits, SoC targets)
– Tariff and demand charge rules
– PV generation and battery SoC (if integrated)
– Priority rules and access policies
– Safety limits (thermal sensors, fault states)
Benefits of Well-Designed Throttling Logic
– Higher overall site uptime and fewer overload-related outages
– Lower energy costs by avoiding demand peaks and expensive periods
– Better user experience through predictable behavior and fewer failed sessions
– Improved scalability: more connectors without immediate grid upgrades
– Operational control for fleets: readiness targets with constrained infrastructure
Limitations to Consider
– Aggressive throttling can increase charge times and frustrate drivers if not communicated
– If power is reduced too much, some EVs may stop charging or behave inconsistently
– Requires accurate metering and reliable control channels; delays can cause overshoot
– Fairness vs readiness trade-offs must be defined (equal share may not meet fleet priorities)
– Complex sites may need commissioning and tuning to avoid unintended peaks
Related Glossary Terms
Active Power Throttling
Load Management
Dynamic Load Balancing
Energy Management System (EMS)
Demand Charges
Peak Shaving
Battery Energy Storage System (BESS)
Renewable Integration