Mi/kWh vs kWh/100km: EV Efficiency Units Explained
Understanding different EV efficiency metrics and how to convert between them.
Learn to read and compare EV efficiency ratings across different regions and standards.
Reviewed by Eldrivo Editorial Team on February 22, 2026. This guide is maintained alongside our calculator methodology and editorial policy.
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Key Takeaways
- ✓Mi/kWh (higher is better) and kWh/100km (lower is better) are the two main EV efficiency metrics, expressing the same concept in inverted units.
- ✓To convert mi/kWh to kWh/100km: divide 62.137 by the mi/kWh value.
- ✓US manufacturers typically use mi/kWh, while European manufacturers prefer kWh/100km.
- ✓Understanding efficiency metrics is essential for accurately comparing vehicles and calculating charging costs.
What Is Mi/kWh and How to Read It
Miles per kilowatt-hour (mi/kWh) measures how far an EV travels on one unit of electrical energy. A higher number means better efficiency. A Tesla Model 3 achieving 4.0 mi/kWh travels 4 miles for every kWh consumed. This metric is intuitive for US drivers because it parallels miles-per-gallon (MPG) — higher is always better. Most US-market vehicles display efficiency in mi/kWh on the dashboard and in EPA ratings. Typical values range from 2.5 mi/kWh for large trucks and SUVs to 4.5 mi/kWh for the most efficient sedans. Knowing your vehicle's real-world mi/kWh allows you to calculate costs quickly: divide your electricity rate by mi/kWh to get cost per mile. At $0.16/kWh and 4.0 mi/kWh, that is $0.04 per mile.
| Excellent efficiency | 4.0+ mi/kWh |
| Good efficiency | 3.5–4.0 mi/kWh |
| Average efficiency | 3.0–3.5 mi/kWh |
| Below average | Under 3.0 mi/kWh |
What Is kWh/100km and How to Read It
Kilowatt-hours per 100 kilometers (kWh/100km) measures how much energy an EV consumes to travel 100 km. A lower number means better efficiency. This metric is standard in Europe and used by WLTP testing. A Hyundai Ioniq 6 at 14.3 kWh/100km uses just 14.3 kWh to cover 100 km, making it one of the most efficient EVs available. This metric is analogous to liters/100km used for fuel economy in most countries outside the US. It is particularly useful for calculating costs: multiply kWh/100km by your electricity rate and divide by 100 to get cost per km. At €0.30/kWh and 16 kWh/100km, that is €0.048 per km. Typical values range from 13 kWh/100km for the most efficient models to 28 kWh/100km for large trucks.
| Excellent efficiency | Under 15 kWh/100km |
| Good efficiency | 15–18 kWh/100km |
| Average efficiency | 18–22 kWh/100km |
| Below average | Over 22 kWh/100km |
Converting Between Mi/kWh and kWh/100km
The conversion between these two metrics uses the relationship: kWh/100km = 62.137 ÷ mi/kWh, and conversely mi/kWh = 62.137 ÷ kWh/100km. The constant 62.137 represents 100 km expressed in miles. For quick mental math, you can approximate with 62: a vehicle rated at 4.0 mi/kWh has an efficiency of about 62 ÷ 4.0 = 15.5 kWh/100km. Going the other direction, a vehicle rated at 20 kWh/100km achieves about 62 ÷ 20 = 3.1 mi/kWh. There is also a third metric — Wh/km (watt-hours per kilometer) — which is simply kWh/100km multiplied by 10. A vehicle rated at 17.5 kWh/100km uses 175 Wh/km. Our calculators handle all conversions automatically, so you can enter your vehicle's efficiency in whichever format you have.
Why Efficiency Matters for Your Wallet
The efficiency difference between EV models has a direct and significant impact on charging costs. Consider two vehicles: an efficient sedan at 4.0 mi/kWh and a large SUV at 2.8 mi/kWh. Over 12,500 miles per year at $0.16/kWh, the sedan costs $500/year to charge, while the SUV costs $714/year — a $214 annual difference solely from efficiency. Over five years, that efficiency gap adds up to over $1,000 in extra charging costs. This is why efficiency should be a key factor when choosing an EV, alongside range, size, and features. Unlike gasoline cars where engine efficiency is hidden behind MPG numbers, EV efficiency is directly tied to your electricity bill. Using our cost calculator, you can see exactly how much different efficiency levels cost at your local electricity rate.
Frequently Asked Questions
How do I convert mi/kWh to kWh/100km?
Divide 62.137 by the mi/kWh value. For example, 4.0 mi/kWh = 62.137 ÷ 4.0 = 15.5 kWh/100km. For quick mental math, use 62 instead of 62.137. This conversion works because 100 km equals approximately 62.137 miles.
What is a good mi/kWh for an EV?
A good efficiency for an EV is 3.5–4.0 mi/kWh (or 15.5–17.8 kWh/100km). Excellent efficiency is above 4.0 mi/kWh, which is achieved by aerodynamic sedans like the Tesla Model 3 and Hyundai Ioniq 6. SUVs and trucks typically achieve 2.5–3.5 mi/kWh, while compact cars can exceed 4.0 mi/kWh.
Which EV efficiency metric should I use?
Use whichever metric your vehicle displays. In the US, mi/kWh is more common. In Europe, kWh/100km is standard. Both express the same information — just inverted. For comparing vehicles across markets, our calculator accepts both formats and handles conversions automatically.
Does EV efficiency change with driving conditions?
Yes, real-world efficiency varies significantly. Highway driving at 75+ mph can reduce efficiency by 15–25% compared to city driving due to aerodynamic drag. Cold weather reduces efficiency by 15–35% due to battery heating and cabin climate control. Aggressive acceleration also hurts efficiency, while gentle driving with regenerative braking improves it.
How does EV efficiency compare to gas MPG?
EVs are roughly 3–4 times more efficient than gasoline cars at converting energy into motion. A 4.0 mi/kWh EV is equivalent to approximately 120 MPGe (miles per gallon equivalent). Even a less efficient EV at 2.8 mi/kWh equals about 84 MPGe, which is far better than any non-hybrid gasoline vehicle.
How this guide is maintained
Eldrivo guides combine explanatory content with the same assumptions used across our calculators and comparison pages. When we update formulas or page-level assumptions, we review guide language to keep explanations aligned.
For exact cost estimates, use the calculators with your own electricity rate, mileage, and charging mix instead of relying only on example numbers.
Estimate your own costs
Run the calculators with your local electricity rate to get a personalized estimate.
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