Convert between electric car efficiency units: mi/kWh, Wh/mi, Wh/km, kWh/100km, km/kWh, and MPGe. Includes conversion formulas, quick reference tables, and technical context.
EV Efficiency Unit Converter
Mathematical Conversion Formulas
Electric car efficiency units fall into two main metrics: Consumption (how much electricity is used over a set distance) and Economy (how far the car goes on a set amount of electricity). To convert between these units, use the base conversion constants below:
Constant: 1 Mile = 1.609344 KilometersConstant: 1 Gallon of Gasoline Equivalent = 33.705 kWh (EPA Standard)
1. Converting Consumption to Economy (Wh/mi to mi/kWh)
To convert energy used per mile to distance per kilowatt-hour, divide 1,000 by the consumption rating:
Miles per kWh (mi/kWh) = 1,000 ÷ Wh/miKilometers per kWh (km/kWh) = (1,000 ÷ Wh/km)
2. Converting Economy to Consumption (mi/kWh to Wh/mi)
To reverse the process and find energy consumed per mile or kilometer:
Wh/mi = 1,000 ÷ (mi/kWh)Wh/km = Wh/mi ÷ 1.609344
3. Converting to MPGe (Miles per Gallon Equivalent)
MPGe measures distance traveled relative to the chemical energy equivalent of one gallon of gasoline (33.705 kWh):
MPGe = mi/kWh × 33.705MPGe = 3,370.5 ÷ (kWh/100 mi)
EV Efficiency Benchmarks Quick Reference Table
This table compares common efficiency classes across the seven primary measurement standards, from highly streamlined commuter cars to large electric trucks.
| Efficiency Tier | mi/kWh | km/kWh | Wh/mi | Wh/km | kWh/100km | MPGe |
|---|---|---|---|---|---|---|
| Excellent (e.g., Hyundai Ioniq 6) | 4.5 mi/kWh | 7.24 km/kWh | 222 Wh/mi | 138 Wh/km | 13.8 kWh/100km | 152 MPGe |
| Good (e.g., Tesla Model Y RWD) | 3.5 mi/kWh | 5.63 km/kWh | 286 Wh/mi | 178 Wh/km | 17.8 kWh/100km | 118 MPGe |
| Average (e.g., Audi Q8 e-tron) | 2.5 mi/kWh | 4.02 km/kWh | 400 Wh/mi | 249 Wh/km | 24.9 kWh/100km | 84 MPGe |
| Low (e.g., Rivian R1T / Hummer EV) | 2.0 mi/kWh | 3.22 km/kWh | 500 Wh/mi | 311 Wh/km | 31.1 kWh/100km | 67 MPGe |
Understanding EV Efficiency Metrics
Gasoline cars are traditionally evaluated on economy (MPG). However, because electricity is sold in kilowatt-hours (kWh) and electric drivetrains operate with high thermodynamic efficiency, additional units are used to describe how a vehicle uses stored charge.
Consumption vs. Economy
- Economy Units (mi/kWh, km/kWh, MPGe): Higher numbers indicate better efficiency. These tell you how far you can travel per unit of energy. Your dashboard often displays these units because they make calculating remaining range simple.
- Consumption Units (Wh/mi, Wh/km, kWh/100km): Lower numbers indicate better efficiency. They represent the exact amount of grid energy required to move a set distance. These units are helpful for calculating long-term energy costs and home charging grid demand.
What is MPGe?
Established by the United States Environmental Protection Agency (EPA) in 2010, MPGe (Miles per Gallon Equivalent) allows consumers to compare alternative fuel vehicles to conventional gasoline models.
Based on standards defined by the National Institute of Standards and Technology (NIST), the chemical energy in one US gallon of gasoline matches 33.705 kilowatt-hours (kWh) of electricity. A car with a rating of 118 MPGe travels 118 miles on 33.705 kWh of electricity.
Variables Affecting Real-World EV Efficiency
Actual energy usage varies from EPA label figures based on real-world driving conditions:
- Speed: Electric motor and drivetrain efficiency is high at lower speeds (urban traffic), but aerodynamic drag increases exponentially at highway speeds (above 65 mph or 105 km/h), causing consumption (Wh/mi) to rise.
- Temperature: Cold weather slows battery chemical reaction times and requires cabin heating. Generating cabin heat in an EV uses high-voltage PTC heaters or heat pumps, drawing power directly from the traction battery and reducing driving range.
- Regenerative Braking: City driving leverages regenerative braking to capture kinetic deceleration energy and return it to the battery cells, preserving overall efficiency.
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