Why can't every car charge at full power?
An office car park with 20 AC charge points of 11 kW. Between 8:00 and 8:30 AM, fourteen cars plug in.
The building's connection leaves 80 kW for charging. Fourteen cars at full power would need 154 kW.
The questionWhy is the connection smaller than the chargers, and what happens to the cars?
Guess firstTwenty cars park for nine hours and each needs about 12 kWh. What average power do they need together?RevealHide
About 27 kW: 240 kWh spread over nine hours. The twenty charge points could deliver 220 kW, eight times as much.
A composed example. Without management the peak would reach 187 kW; with it, the same energy flows over a longer time, and every car is full long before 5 PM.
Why the connection is smaller
- Cost. A larger connection costs more to build and, in many tariffs, more every month.
- Grid. The local grid may simply not have more capacity, or only after works that take years (see Charging infrastructure, stop 02).
- Need. Cars that park for hours need far less power than their charge points could deliver.
Energy matters more than power
A car that stands for nine hours does not need 11 kW; it needs enough kWh by the evening. turns a peak into a plateau: the same energy, spread over the time the cars stand anyway. The units behind this are explained in eMobility and EV basics, stop 04.
Check your understanding
3 questions. Answer all of them to complete this stop. Each answer explains itself.
Why is the building's connection smaller than the sum of all charge points?
Cost, grid capacity and actual need all point the same way: cars standing for hours need energy, not peak power.
What does load management change for a car parked for nine hours?
The energy reaches the car over a longer time. By the evening, the result is the same.
Twenty cars each need 12 kWh over nine hours. What average power do they need together?
20 × 12 kWh = 240 kWh; divided by 9 hours, about 27 kW.
- Load management Shares a site's grid connection between the cars charging at the same time. EV charging fundamentals, stop 04 Glossary