Peak demand is the maximum electrical power drawn by a site (or a specific load group) during a defined period. It is typically measured in kilowatts (kW) or kilovolt-amperes (kVA) and can be tracked as an instantaneous peak or as a utility-defined demand interval (commonly 15 or 30 minutes).
In EV charging, peak demand often refers to the maximum combined load from chargers plus other building loads at the same time.
Why Peak Demand Matters in EV Charging
Peak demand directly affects electrical design, operating costs, and scalability. Managing it helps:
– Avoid tripping the main fuse or exceeding the import capacity
– Reduce demand charges where utilities bill based on peak kW
– Prevent costly grid upgrades (transformer, feeder, switchboard reinforcement)
– Improve reliability for multi-charger sites, fleets, and multi-tenant buildings
– Enable more chargers within the same connection limit using load management
How Peak Demand Is Created
Peak demand typically occurs when multiple loads operate simultaneously:
– EV chargers start charging at the same time (arrival patterns, shift changes)
– HVAC, lifts, cooking equipment, or industrial machinery run concurrently
– Seasonal peaks (winter heating or summer cooling) overlap with charging
– Unmanaged charging ramps up during the same interval used for billing demand
Peak Demand in EV Charging Sites
At charging locations, peak demand can be driven by:
– Number of active charge points and their set power limits (e.g., 10 × 22 kW)
– Vehicle onboard charger limits and charging behavior
– Simultaneity factor (how many chargers run at full power at once)
– Phase imbalance in single-phase heavy sites
– Mixed AC and DC loads (depots with exception DC fast chargers)
How Peak Demand Is Measured and Controlled
Peak demand is usually tracked via:
– Building meters or interval metering
– Load measurement and real-time monitoring modules in LV panels
– CPMS dashboards showing site-level load and per-charger draw
Peak demand is controlled by:
– Dynamic load balancing against a site limit
– Load shedding or throttling chargers during peaks
– Scheduled charging and staggered start times (especially for fleets)
– On-site energy storage or solar (where applicable)
– Setting a maximum site demand limit for the EV load group
Key Benefits of Peak Demand Management
– Lower operating costs (reduced demand charges and penalties)
– More charge points without immediate grid upgrades
– Better user experience (fewer faults, stable charging sessions)
– Improved safety and thermal performance in cables and switchgear
– Better planning for future expansion phases
Limitations and Considerations
– Limiting peak demand can reduce charging speeds during busy periods
– Requires accurate measurement and stable communications between chargers and controllers
– Poorly configured limits can cause driver dissatisfaction if not communicated
– Demand billing rules vary by utility and region, affecting ROI calculations
Related Glossary Terms
Maximum Demand
Maximum Site Demand Limit
Demand Charges
Import Capacity
Load Management
Load Balancing
Load Shedding
Load Shifting
Interval Metering
Load Profile
Peak Shaving