Peak demand logging is the continuous measurement and recording of a site’s highest electrical demand (typically in kW or kVA) over time, usually aligned to utility-defined demand intervals (often 15 or 30 minutes). For EV charging sites, it captures when and why demand peaks occur—across chargers and other building loads—and stores this data for analysis, reporting, and control.
Why Peak Demand Logging Matters in EV Charging
Peak demand logging is essential for cost control and reliable scaling because it helps operators and site owners:
– Identify the true drivers of peaks (chargers vs HVAC vs production loads)
– Reduce demand charges where billing is based on maximum kW
– Verify compliance with maximum site demand limits or grid connection agreements
– Tune load management and prevent trips of main breakers/fuses
– Plan expansions using evidence (not assumptions)
– Support audits, tenant billing, and energy reporting
How Peak Demand Logging Works
A typical peak demand logging setup includes:
– Metering or power measurement at the site incomer (and optionally per charger group)
– Time-stamped interval data stored in a database (CPMS, EMS, BMS, or SCADA)
– Calculations that track:
– Maximum demand per interval (rolling maximum)
– Daily/weekly/monthly peak values
– Peak time-of-day patterns and seasonal variations
– Dashboards/alerts that notify when demand approaches limits
Where Peak Demand Logging Data Comes From
Common data sources in EV charging projects include:
– Utility or building interval meters (main supply meter)
– Sub-metering in LV panels (CTs/energy meters for charger feeders)
– Charge Point Management System (CPMS) site-level load aggregation
– Building Management Systems (BMS) for non-EV loads
– Grid monitoring modules at the PCC for sites with strict connection rules
What a Good Peak Demand Log Captures
To be actionable, logs typically include:
– kW/kVA demand per interval and the maximum recorded value
– Per-phase currents/voltages where relevant (phase imbalance detection)
– Charger group demand vs total site demand
– Charger utilization metrics (active sessions, power setpoints, throttling events)
– Event markers: load shedding, faults, tariff changes, shift start times
– Alarms: “80% of site limit,” “limit exceeded,” “meter offline”
Key Benefits
– Evidence-based tuning of dynamic load balancing and scheduling
– Lower operating costs through reduced peak charges and penalties
– Improved reliability by detecting abnormal peaks and system issues early
– Better CAPEX planning by understanding real simultaneity and headroom
– Stronger reporting for landlords, fleets, and multi-tenant cost allocation
Limitations and Practical Considerations
– Requires accurate time sync and stable data collection (avoid gaps)
– Different utilities use different demand interval rules and billing definitions
– CPMS-only data may miss non-EV loads unless integrated with building metering
– Storing high-resolution data increases data volume and retention requirements
– Data privacy and security controls apply when logs are tied to users or vehicles
Related Glossary Terms
Peak Demand
Maximum Demand
Demand Charges
Interval Metering
Load Measurement
Load Profile
Load Management
Dynamic Load Balancing
Maximum Site Demand Limit
Energy Management System (EMS)