Formulas
Energy added = Battery × (Target % − Start %)
Energy from grid = Energy added ÷ Efficiency
Cost = Energy from grid × Price per kWh
Energy from grid = Energy added ÷ Efficiency
Cost = Energy from grid × Price per kWh
Example: Charging a 75 kWh battery from 20% to 80% adds 45 kWh. At 90% efficiency you draw 50 kWh; at $0.17 per kWh the charge costs $8.50 and adds about 158 miles (5.4¢ per mile). A 30-MPG gas car at $3.20 a gallon costs 10.7¢ per mile.
Cutting charging costs
- Use your utility’s time-of-use or EV rate and charge overnight.
- Charge to 80% for daily driving — it is faster and easier on the battery.
- Check whether workplace or retail chargers are free.
Financing the car? The auto loan calculator shows the monthly payment.
Frequently asked questions
How much does it cost to charge an electric car?
Energy added ÷ charging efficiency × price per kWh. Charging a 75 kWh battery from 20% to 80% at $0.17/kWh and 90% efficiency costs about $8.50.
How much does an EV cost per mile?
Price per kWh ÷ miles per kWh. At $0.17 and 3.5 mi/kWh that is about 5.4¢ a mile, versus about 10.7¢ for a 30-MPG car with gas at $3.20.
Why include charging efficiency?
Some energy is lost as heat in the charger and battery. Level 2 home charging is about 88–92% efficient; Level 1 (a standard outlet) is lower.
Is public fast charging more expensive?
Usually yes. DC fast chargers often cost $0.35–$0.60 per kWh — two to three times home rates — which can make an EV cost as much per mile as an efficient gas car.