How this calculation works
A fleet can have enough energy available over a day yet still miss a departure because several vehicles need it in the same short window. This page allocates charging power slot by slot, keeping the site ceiling, plug count and individual vehicle power limits separate.
Grid energy required = battery energy/efficiency; each whole slot allocates available kW by earliest departure, limited by plugs and vehicle powerA worked example
The two vans each require eighteen battery kWh at ninety percent efficiency, or twenty grid kWh each. With ten-kW vehicle limits and two plugs, the example can deliver all thirty-six battery kWh within their entered windows. Reducing the site power to five kW makes the deadlines much tighter even though two physical plugs remain. More plugs do not create electrical capacity, and more site power cannot help a vehicle whose own power limit is already binding.
Good to know
Slot-average scheduling only; no battery taper, SOC curve, tariff, fixed plug assignment, hardware control or optimal feasibility guarantee. The assumptions are not an electrical installation design. Validate real charging curves, utility supply, charger compatibility and departure requirements before making infrastructure commitments.
Reference: US Department of Energy — electric vehicles for fleets (opens in a new tab) ↗
What this model answers
A fleet can have enough energy available over a day yet still miss a departure because several vehicles need it in the same short window. This page allocates charging power slot by slot, keeping the site ceiling, plug count and individual vehicle power limits separate.
Vehicles with earlier departure times receive priority among those available for a complete slot. That earliest-deadline rule is a transparent heuristic. It is not an optimization proof and a shortfall under this schedule does not prove every possible schedule would fail.
The Delivery route time windows calculator follows the travel and service timeline. Charging windows must be based on genuine depot dwell periods; a route return time can inform an arrival assumption but does not supply battery energy needs.
Measure the right inputs
Enter battery energy still required, not total battery capacity or driving distance. The calculator reverses your grid-to-battery efficiency to obtain grid energy demand. Vehicle power is a grid-side limit so losses are not applied twice.
Arrival and departure are hours from one origin. Only slots lying entirely within that interval are used. A vehicle arriving halfway through a thirty-minute slot cannot charge until the next slot; changing to fifteen-minute slots can reduce that deliberate conservatism.
Read the result in context
The load graph shows slot-average power, not an instantaneous charger trace. A vehicle that completes its energy allocation early still occupies its plug for that whole modeled slot. Another vehicle cannot inherit a fractional leftover plug-time within that slot.
Read unmet battery energy separately for each vehicle. Summed delivered battery energy should equal grid energy multiplied by the entered efficiency. The simulation assumes vehicles can change plugs between slots without travel or reconnection time.
Work through the numbers
The two vans each require eighteen battery kWh at ninety percent efficiency, or twenty grid kWh each. With ten-kW vehicle limits and two plugs, the example can deliver all thirty-six battery kWh within their entered windows.
Reducing the site power to five kW makes the deadlines much tighter even though two physical plugs remain. More plugs do not create electrical capacity, and more site power cannot help a vehicle whose own power limit is already binding.
Where the model stops
Slot-average scheduling only; no battery taper, SOC curve, tariff, fixed plug assignment, hardware control or optimal feasibility guarantee.
The assumptions are not an electrical installation design. Validate real charging curves, utility supply, charger compatibility and departure requirements before making infrastructure commitments.
A few questions, answered
Why can finer slots change the result?
They capture more usable time around arrivals and departures and allow earlier modeled reassignment of plugs.
Is battery kWh the same as grid kWh?
No. With efficiency below one hundred percent, the grid must supply more energy than reaches the battery.