EV charging calculator
Enter your battery and charger, get the charging time and cost.
How long does it take to charge an electric car?
Energy needed ÷ charger power. Taking a 75 kWh battery from 20% to 80% puts in 45 kWh; with 90% charging efficiency that is 50 kWh from the grid, about 6.9 hours on a 7.2 kW Level 2 charger.
How fast are Level 1 and Level 2 chargers?
Level 1 is a 120-volt plug — the Department of Energy figures about 1.9 kW, or roughly 5 miles of range per hour. Most home Level 2 chargers run at up to 30 amps on 240 volts, delivering 7.2 kW; Level 2 units range from 2.9 to 19.2 kW.
How much does it cost to charge an EV?
Energy from the grid × your electricity price: 50 kWh at 15¢ per kWh is $7.50. Use the price per kWh on your electric bill.
How much energy is lost while charging?
Some — fueleconomy.gov puts battery charging efficiency at often 84% to 93%. The calculator uses 90% unless you change it.
Why does fast charging slow down near the end?
To protect the battery: as it reaches about 80%, the charging power drops, and the last 10–20% charges slowly, per the Department of Energy. The time shown assumes steady power, so charging past 80% on a fast charger takes longer than shown.
Can I charge overnight from a regular outlet?
It adds a modest amount. At the 1.9 kW the Department of Energy quotes for Level 1, a 12-hour night draws about 22.8 kWh from the wall, and at 90% efficiency roughly 20.5 kWh reaches the battery. That fits a short commute but will not refill a large battery from a low level; the table under the result shows other charger powers.
Why not charge to 100% every time?
The calculator lets you set any start and end level, and most people use a range such as 20% to 80%, because that is where fast charging is quickest. The DOE notes that charging power drops as the battery fills. Check your car’s manual for the manufacturer’s advice on charge limits.
The formula
Energy added to the battery = capacity × (end % − start %) ÷ 100. Energy drawn from the grid = energy added ÷ charging efficiency. Time = energy from the grid ÷ charger power, and cost = energy from the grid × price per kWh. The time assumes constant power from start to end, which is closest to true for a home Level 2 charger and least true for a DC fast charger, whose power tapers as the battery fills.
Worked example: 60 kWh battery, 10% to 90%
The battery gains 60 × 0.80 = 48 kWh. At 90% efficiency the grid supplies 53.3 kWh. On a 7.2 kW Level 2 charger that takes 7.4 hours and, at 15 cents per kWh, costs $8.00. On a 1.9 kW Level 1 outlet the same energy takes 28.1 hours, about 1.2 days, and costs the same $8.00: the price depends on the energy, not on how fast it arrives. Adding 20 percentage points on Level 1 (20% to 40%) takes 7.0 hours.
Common mistakes
Using the nameplate power of the car’s onboard charger when the wall unit supplies less (or the reverse) gives the wrong time, because the slower of the two sets the pace. Forgetting efficiency understates both the time and the bill. Treating a public fast-charging price as your home price is another: networks often charge more per kWh than a home utility, and some bill by the minute or with session fees, which this calculator does not model. For the circuit a home charger needs, see the EV charger circuit calculator.
Sources: U.S. Department of Energy, Alternative Fuels Data Center (charging levels and the slowdown of charging near full) and fueleconomy.gov (charging efficiency). Related: EV charger circuit calculator, EV vs gas calculator, electricity cost calculator and MPGe calculator.