What Duty Cycle Analysis Is
Duty cycle analysis is the evaluation of how a vehicle, charger, or fleet is used over time — including operating periods, idle periods, energy consumption, and charging windows. In EV fleets and charging infrastructure planning, it’s the core method for determining how much energy is needed, when it’s needed, and what charging power and bay count will reliably meet operational schedules.
Why Duty Cycle Analysis Matters
Duty cycle analysis prevents under-designed sites (missed departures) and over-designed sites (wasted CAPEX):
– Right-sizes charger count and power (AC vs DC)
– Predicts peak simultaneity and supports depot power management
– Identifies the best charging windows (overnight, between shifts, opportunity charging)
– Helps estimate grid connection needs and avoid unnecessary upgrades
– Improves total cost of ownership through smarter energy scheduling
What a Duty Cycle Looks Like in Practice
A duty cycle typically maps:
– Vehicle departure and return times
– Distance driven and route energy demand (kWh/day)
– Idle/dwell time at depot or destinations
– Charging opportunities and constraints (site cap, tariff windows)
– Operational exceptions (late returns, seasonal peaks, spare vehicles)
Key Inputs for Fleet Duty Cycle Analysis
To produce a useful analysis, you usually need:
– Vehicle types, battery sizes, and charging limits
– Route profiles: km/day, stop density, payload impacts
– Consumption benchmarks (kWh/100 km) by season and route type
– Shift structure: single-shift vs multi-shift operations
– Depot constraints: site power cap, existing building load, bay layout
– Required SOC targets by departure (buffers for delays and detours)
– Tariffs and demand charges (if optimizing cost as well as readiness)
Core Outputs and Decisions
A good duty cycle analysis typically produces:
– Required energy per vehicle per shift (kWh)
– Required charging time windows and minimum charging power
– Charger quantity and bay allocation (including priority bays)
– Site peak demand profile and recommended load management strategy
– Risk scenarios: what happens on worst-case days (cold weather, late returns)
– Expansion plan: how the solution scales as the fleet grows
Common Analysis Methods
– Energy balance method: daily energy need vs available charging hours
– Simultaneity modeling: how many vehicles charge at once under realistic behaviour
– Constraint-based scheduling: allocate power under a site kW cap to meet deadlines
– Scenario testing: best case / typical / worst case operations
– Sensitivity analysis: impact of colder weather, new routes, more vehicles, tariff shifts
Typical Pitfalls
– Using average km/day without considering peak days and seasonality
– Ignoring dwell time variability (late arrivals compress the charging window)
– Assuming high diversity at depots without enforced load management
– Not including building load peaks (warehouses, refrigeration, HVAC)
– Underestimating driver behaviour effects (plug-in compliance, bay blocking)
– Designing for today only, with no growth pathway
Related Terms for Internal Linking
– Fleet duty cycle
– Depot energy optimization
– Depot power management
– Charging capacity planning
– Charging schedules
– Demand charges
– Diversity factor
– Charging utilization