Electric Vehicle Efficiency: MPGe, kWh per 100 Miles, and Cost per Mile

Conversion Formulas

MPGe = 33.7 × miles per kWh = 3,370 ÷ (kWh per 100 miles). Miles per kWh = 100 ÷ (kWh per 100 miles). In metric terms, 25 kWh per 100 miles is 15.5 kWh per 100 km, or 6.4 km per kWh. Typical modern EVs consume 25 to 35 kWh per 100 miles (4.0 to 2.9 miles per kWh), and efficient models can reach 22 or less. Larger trucks and SUVs may use 40 to 55 kWh per 100 miles.

The EPA label lists the kWh per 100 miles and MPGe. Real-world consumption depends on speed, temperature, terrain, tires, and driving style, and is typically 10% to 30% higher in cold weather.

Charging Costs

Cost per mile = (kWh per 100 miles ÷ 100) × price per kWh ÷ charging efficiency. Charging losses are typically 10% to 15%, so for a car using 25 kWh per 100 miles from the battery at $0.16/kWh at home, the cost is about 0.25 × 0.16 ÷ 0.88 = 4.5 cents per mile. A year of 12,000 miles costs about $545, compared with 12,000 miles at 30 mpg and $3.60 gasoline, which is $1,440, or 12 cents per mile. Public fast charging often costs $0.35 to $0.60 per kWh, giving 9 to 15 cents per mile at 25 kWh per 100 miles, which can approach gasoline costs.

Time-of-use rates, solar panels, and workplace charging can reduce costs further.

Comparing With Gasoline Cars

For fair comparisons, compute energy cost per mile for each car. At $0.16 per kWh, home charging costs about 4.5 cents per mile at 25 kWh per 100 miles. A 30-mpg gasoline car at $3.60 per gallon costs 12 cents per mile. A hybrid at 50 mpg costs 7.2 cents. Break-even electricity prices: the EV costs the same as the 30-mpg car at about $0.42 per kWh (home charging losses included). Consider also maintenance savings (fewer moving parts) and the higher purchase price of many EVs. A total cost of ownership analysis over 5 to 10 years, including incentives, is the right framework.

Range and Battery Size

Range equals usable battery capacity divided by consumption. A 75 kWh pack at 25 kWh per 100 miles gives 300 miles. At highway speeds, consumption rises: driving at 75 mph may use 35% more energy than 55 mph. Cold weather reduces range through battery chemistry and cabin heating, often by 20% to 30% in freezing temperatures. Plan charging stops accordingly. Charging from 10% to 80% is typically faster than 80% to 100%, which slows down to protect the battery.

Practical Tips

Charge at home overnight when electricity is cheapest, use preconditioning while plugged in, keep tires properly inflated, and use regenerative braking. Track your actual kWh per 100 miles using the car's display, and compare with the sticker to understand your driving.