Free Home EV Charging Time calculator with clear step-by-step results.
Charging time is the energy the battery needs divided by charger output, but the grid has to supply more than the battery receives because of conversion and thermal losses. Applying charging efficiency to the grid side is what makes both the time and the cost figures come out right.
Energy needed
Battery kWh = usable capacity x (target SOC - start SOC) / 100
Charging time
Hours = battery kWh / charging efficiency / charger kW
AC charging tapers above roughly 80% on many vehicles, and staying below it reduces calendar ageing of the cells. Charge to 100% when you need the full range.
Only if the vehicle's onboard charger can accept it. Many models are limited to 3.6 or 7.4 kW single phase regardless of what the wallbox can supply.