Peak shaving is an energy management strategy that reduces a site’s peak demand (the highest kW/kVA draw) by temporarily limiting, shifting, or supplying part of the load from alternative sources. In EV charging, peak shaving is used to keep total site power below a maximum site demand limit, avoid overloading electrical infrastructure, and reduce costs where demand charges apply.
Why Peak Shaving Matters in EV Charging
EV charging can add large, simultaneous loads—especially at fleet depots, workplaces, and multi-tenant sites. Peak shaving helps operators and site owners:
– Avoid tripping the main breaker or exceeding import capacity
– Reduce demand charges and peak-related penalties (tariff-dependent)
– Delay or reduce the need for grid upgrades (transformer, feeders, switchboards)
– Increase the number of chargers supported within existing capacity
– Improve reliability and predictability during high-demand periods
How Peak Shaving Works
Peak shaving typically combines monitoring and control to keep demand under a target threshold:
– Measure total site demand using interval metering or real-time power meters
– Define a site limit (contracted capacity, main fuse rating, or operational threshold)
– When demand approaches the limit, reduce EV load via load management
– Optionally supply shortfalls using battery energy storage (BESS) or on-site generation
– Restore normal charging power when demand falls below the threshold
Common Peak Shaving Methods for EV Charging
– Dynamic load balancing: throttle chargers in real time to stay under a site limit
– Load shifting: move charging to off-peak hours (e.g., scheduled overnight charging)
– Staggered charging starts: prevent simultaneous ramp-up (especially for fleets)
– Priority-based control: allocate power to vehicles with earliest departures or lowest SoC
– BESS-assisted shaving: batteries discharge during peaks and recharge off-peak
– PV + smart charging coordination: align charging with on-site solar output (site-dependent)
Where Peak Shaving Is Commonly Used
– Fleet depots with many vehicles plugging in at the same time
– Workplace charging with morning/afternoon building load peaks
– Retail and mixed-use properties with limited electrical headroom
– Multi-tenant residential sites with synchronized evening charging
– Sites with strict grid connection limits or expensive capacity upgrades
Key Benefits
– Lower peak-related costs and improved tariff performance
– More chargers and higher utilization without immediate grid reinforcement
– Reduced risk of overload events and nuisance trips
– Better planning and scalability for phased infrastructure rollout
– Improved operational control through data and automation
Limitations and Considerations
– Throttling can increase charging time during busy periods
– Battery-based peak shaving adds CAPEX, space, and maintenance requirements
– Effectiveness depends on utility demand interval rules and tariff structure
– Requires accurate monitoring, time sync, and reliable control communications
– Poorly tuned limits can reduce user satisfaction or create queues
Related Glossary Terms
Peak Demand
Demand Charges
Maximum Site Demand Limit
Import Capacity
Interval Metering
Load Management
Load Balancing
Load Shifting
Peak Demand Profiling
Battery Energy Storage System (BESS)