How to Use the EV Charging Loss & Real Cost Calculator
The kWh number shown on a charging station is how much power it delivered, not necessarily how much ends up stored in the battery. Some energy is lost during conversion, and how much depends on the charging method.
Level 2 (AC) charging routes power through the car's onboard charger, which typically loses around 10% along the way. DC fast charging delivers direct current straight to the battery, so losses tend to be lower — closer to 5%. This calculator takes the displayed kWh and charging method and shows you the real amount stored in the battery, plus what the loss actually cost you.
Because most networks bill based on the delivered kWh shown on the charger rather than what actually lands in the battery, higher-loss charging means you're paying more per mile of real range than the sticker price suggests. If you rely mostly on Level 2 charging, factoring this in gives a more accurate picture of your true cost per mile.
Actual loss rates shift with battery temperature, cable length, and how worn the charging equipment is, so the figures here are reasonable averages rather than exact numbers. If you want a precise reading, compare the state of charge (SOC) before and after a session against the kWh the charger reported.
Frequently Asked Questions
Level 2 (AC) charging typically loses around 10% during conversion, while DC fast charging loses closer to 5%. Actual loss varies with battery temperature and cable length.
Most charging networks bill based on the kWh the charger delivered, which is the number shown on the display — not the smaller amount that actually ends up stored in the battery.