What this tool does
This tool converts electric vehicle (EV) efficiency from miles per kilowatt-hour (mi/kWh) to kilowatt-hours per 100 miles (kWh/100 mi). These are two of the most common ways to express EV energy consumption in the United States. Miles per kWh tells you how far an EV can travel on a single kilowatt-hour of electricity, while kWh per 100 miles indicates how much energy is required to cover a standardized distance of 100 miles. The EPA uses the kWh per 100 miles format on new vehicle window stickers, making it the standard metric for comparing efficiency across different electric vehicles sold in the US market. By entering your vehicle's mi/kWh rating, you instantly get the equivalent kWh/100 mi value along with related metrics like MPGe (miles per gallon equivalent) and watt-hours per mile.
How it works
The conversion uses a straightforward inverse relationship formula:
kWh per 100 miles = 100 / miles per kWh
This works because miles per kWh measures distance per unit of energy, while kWh per 100 miles measures energy per unit of distance. They are inversely proportional. If an EV gets 4 mi/kWh, it uses 0.25 kWh per mile, which scales to 25 kWh per 100 miles.
The tool also calculates MPGe (miles per gallon equivalent) using the EPA standard where 1 gallon of gasoline contains 33.705 kWh of energy. The formula is: MPGe = miles per kWh multiplied by 33.705. This allows direct comparison between electric and gasoline vehicle efficiency using a familiar unit. Additional metrics include kWh per mile and watt-hours per mile, which are useful for calculating trip energy costs and comparing with charging station pricing that is often listed per kWh.
Who should use this
1. Electric vehicle owners who want to understand their car's EPA efficiency rating in kWh/100 mi format, which appears on the Monroney sticker and is used for official comparisons. 2. Car shoppers comparing electric vehicles side by side, since manufacturers sometimes report efficiency in mi/kWh while the EPA uses kWh/100 mi. 3. Fleet managers tracking energy costs across electric vehicle fleets who need to convert between efficiency formats for standardized reporting. 4. Automotive journalists and reviewers translating real-world test results into the formats their readers expect. 5. EV enthusiasts monitoring their driving efficiency through onboard displays that show mi/kWh and wanting to compare against EPA benchmarks listed in kWh/100 mi. 6. Energy analysts estimating electricity demand from EV adoption using per-mile consumption rates.
Worked examples
Example 1: A Tesla Model 3 achieves 4.0 mi/kWh in normal driving conditions.
kWh/100 mi = 100 / 4.0 = 25.00 kWh/100 mi MPGe = 4.0 x 33.705 = 134.8 MPGe kWh per mile = 1 / 4.0 = 0.25 kWh/mi Wh per mile = 0.25 x 1000 = 250 Wh/mi
At an electricity rate of \$0.12/kWh, this vehicle costs \$3.00 per 100 miles to operate.
Example 2: A Rivian R1T pickup truck gets 2.6 mi/kWh during a road trip.
kWh/100 mi = 100 / 2.6 = 38.46 kWh/100 mi MPGe = 2.6 x 33.705 = 87.6 MPGe kWh per mile = 1 / 2.6 = 0.385 kWh/mi Wh per mile = 0.385 x 1000 = 384.6 Wh/mi
At the same \$0.12/kWh rate, this truck costs \$4.62 per 100 miles to operate.
Example 3: A Hyundai Ioniq 6 achieves an impressive 4.2 mi/kWh.
kWh/100 mi = 100 / 4.2 = 23.81 kWh/100 mi MPGe = 4.2 x 33.705 = 141.6 MPGe
This makes the Ioniq 6 one of the most efficient EVs available, consuming about 38 percent less energy per mile than the R1T truck in Example 2.
Limitations
1. Real-world efficiency varies significantly based on driving speed, ambient temperature, terrain, use of climate control, and driving style. The conversion assumes a fixed efficiency value that may not represent all conditions. 2. Cold weather can reduce EV efficiency by 20 to 40 percent due to battery heating requirements and increased cabin heating loads, meaning actual kWh/100 mi values may be much higher than rated. 3. Highway driving at speeds above 65 mph typically reduces efficiency compared to city driving, unlike gasoline vehicles where highway fuel economy is usually better. 4. The MPGe calculation uses the EPA thermal equivalence of 33.705 kWh per gallon, which measures energy content but does not account for differences in how electricity and gasoline are produced, transmitted, and used. 5. Battery degradation over time reduces effective efficiency, so a vehicle that achieved 4.0 mi/kWh when new may only manage 3.6 mi/kWh after several years of use. 6. Regenerative braking efficiency varies by model and driving conditions, affecting the actual energy consumed per mile in stop-and-go versus highway driving.
FAQs
Q: What is a good kWh per 100 miles rating for an electric vehicle? A: Most modern EVs fall between 25 and 35 kWh per 100 miles. Highly efficient sedans like the Hyundai Ioniq 6 or Tesla Model 3 achieve around 23 to 25 kWh/100 mi, while larger SUVs and trucks typically range from 35 to 45 kWh/100 mi. Lower numbers indicate better efficiency.
Q: How does kWh per 100 miles relate to fuel cost? A: Multiply your kWh/100 mi value by your electricity rate. For example, at \$0.12 per kWh, a vehicle rated at 30 kWh/100 mi costs \$3.60 per 100 miles. Compare this to a 30 MPG gasoline car at \$3.50 per gallon, which costs \$11.67 per 100 miles, making the EV roughly three times cheaper to fuel.
Q: What does MPGe mean and why is it included? A: MPGe (miles per gallon equivalent) is an EPA metric that converts electric efficiency into a gasoline-equivalent format. It uses the fact that one gallon of gasoline contains 33.705 kWh of energy. An EV rated at 100 MPGe can travel as far on 33.705 kWh of electricity as a 100 MPG gasoline car could on one gallon of fuel.
Q: Why do EV dashboards show mi/kWh instead of kWh/100 mi? A: Most EV dashboards display mi/kWh because it behaves like a real-time fuel economy gauge where higher numbers mean better efficiency, which is more intuitive for drivers. The EPA uses kWh/100 mi on window stickers because it is easier to use for calculating total energy costs over a given distance.
Q: How does speed affect EV efficiency? A: Aerodynamic drag increases with the square of speed, so highway driving at 75 mph can consume 30 to 50 percent more energy per mile than driving at 55 mph. An EV rated at 4.0 mi/kWh at moderate speeds might only achieve 2.8 mi/kWh at sustained highway speeds, significantly increasing the kWh/100 mi value.
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