How the estimate works
The calculator first determines how much battery energy is needed: usable battery capacity multiplied by the percentage-point increase. It then uses the lower of the charger rating and the vehicle’s acceptance limit. The practical estimate adds the charging loss you entered, a modest allowance for changing power below 80%, and a larger taper allowance for energy added above 80%.
The fastest road-trip session is often the one that ends when charging power drops—not necessarily when the display reaches 100%.
The U.S. Department of Energy notes that charging time depends on battery depletion, capacity, battery type, the vehicle’s internal charging capacity, charger power, and electrical service. See the Alternative Fuels Data Center charging overview.
Frequently asked questions
Why is practical charging time longer than battery kWh divided by charger kW?
The car may accept less power than the charger can supply, charging incurs losses, and DC charging power generally falls as the battery approaches a high state of charge.
Does a 350 kW charger always charge at 350 kW?
No. Actual power is limited by the vehicle, battery temperature, state of charge, station power sharing, and charger conditions.
Why does the estimate slow down above 80%?
Most EVs reduce charging power at high state of charge to protect the battery. The exact charging curve varies by model and conditions.