Load balancing is a method of automatically distributing available electrical power across one or multiple EV chargers to prevent the site from exceeding its grid connection limit or main breaker capacity. In EV charging, load balancing keeps charging reliable and safe by adjusting charging current in real time based on building consumption, charger demand, and defined priority rules.
What Is Load Balancing?
Load balancing (also called dynamic load management) continuously monitors site load and allocates power to chargers so the total stays within a safe limit. It can work:
– Within a single charger (e.g., splitting power between two sockets)
– Across a group of chargers in a shared electrical feed
– Across an entire site, accounting for building loads like HVAC, lighting, and machinery
Load balancing typically adjusts charging by changing the current limit (A) per connector or per charger.
Why Load Balancing Matters in EV Charging Infrastructure
Without load balancing, multiple EVs charging at the same time can overload the electrical connection, causing:
– Tripped breakers and site downtime
– Reduced charger availability and poor user experience
– Costly grid upgrades or larger main connections
Load balancing enables scalable deployments by maximizing existing electrical capacity while maintaining compliance with electrical protection limits and site constraints.
How Load Balancing Works
A typical load balancing system includes:
– A measurement point (smart meter, CT clamps, or energy meter) tracking total site consumption
– A controller (charger controller, gateway, or CPMS) applying site rules
– Chargers that can accept real-time setpoints (often via OCPP)
The control logic usually follows steps:
– Measure current site load and remaining headroom to the main limit
– Calculate available power for EV charging
– Distribute power across active charging sessions
– Update charger current limits continuously (seconds to minutes)
If headroom decreases (e.g., building load spikes), charging power is reduced. If headroom increases, chargers can ramp up again.
Types of Load Balancing
Load balancing can be configured in different ways depending on the site:
– Static load balancing: fixed maximum per charger group (no live building measurement)
– Dynamic load balancing: real-time adjustment based on actual building consumption
– Local load balancing: chargers balance power within a cluster without cloud dependence
– Centralized load balancing: a site controller or backend coordinates many chargers
– Phase-aware load balancing: considers phase distribution to avoid unbalanced currents in three-phase systems
Key Benefits of Load Balancing
– Prevents overloads and improves electrical safety
– Enables more chargers on the same connection without major upgrades
– Improves site uptime and user experience
– Supports smarter energy strategies like peak shaving and demand management
– Helps optimize CAPEX by reducing transformer, cabling, and switchgear oversizing
Limitations and Practical Considerations
Load balancing is not a substitute for adequate electrical design. Important considerations include:
– Measurement accuracy (CT orientation, meter calibration, update rate)
– Network reliability and fallback behavior if communication fails
– Minimum charging current requirements (EVs may stop below certain thresholds)
– Fairness and priority rules (first-come-first-served, equal share, fleet priority)
– Electrical constraints such as phase imbalance, cable limits, and breaker ratings
Poor configuration can cause unstable charging, frequent ramping, or uneven user experience.
Load Balancing in AC vs DC Charging
– In AC charging, load balancing typically changes the AC current limit per connector (e.g., 6–32 A)
– In DC fast charging, power sharing can be more complex because chargers allocate DC power across dispensers and may coordinate with battery acceptance limits
In both cases, the EV and charger work together to apply the requested power safely.
Related Glossary Terms
Dynamic load management
Peak shaving
Demand response
Phase balancing
Power throttling
Charge Point Management System (CPMS)
OCPP
Smart metering
Site power limit