How to calculate EV charging cost
Multiply usable battery capacity by the percentage points being added to find energy stored in the battery. Because some electricity is lost as heat and used by battery conditioning, divide by charging efficiency to estimate energy measured by the utility meter. Charging cost is wall energy multiplied by your electricity rate.
Wall kWh = battery kWh added ÷ charging efficiency
Charging cost = wall kWh × electricity price
Why charging losses matter
The battery may gain 45 kWh while the wall supplies 50 kWh. Ignoring that difference understates the bill. Losses vary with temperature, equipment, battery conditioning and charging speed. If you do not have measured data, 85–92% is a useful scenario range.
EV charging time estimate
Estimated time equals wall energy divided by charger power. Real charging can take longer because the vehicle and station may not hold their rated power continuously, especially near a high state of charge. For home charging, use the lower of the EV’s onboard charger limit and the charging station’s rated output.
Home rate vs. public charging price
Enter the full per-kWh price for the session. A home rate may include generation and delivery charges. Public networks can add session, idle or parking fees, which are not included in a per-kWh calculation and should be added separately.