EV efficiency explained: mi/kWh, kWh/100mi, and MPGe
The three numbers you see on EV window stickers and reviews — mi/kWh, kWh/100mi, and MPGe — are all measuring the same thing, just in different units. Here's how to read each one, when to use it, and the typical numbers across the EV market.
The short version
- mi/kWh — miles driven per kilowatt-hour. Higher is better. Typical EV: 3–4 mi/kWh.
- kWh/100mi — energy used to drive 100 miles. Lower is better. Typical EV: 25–33 kWh/100mi.
- MPGe — miles per gallon equivalent. Higher is better. EPA defines 1 gallon = 33.7 kWh of energy. Typical EV: 100–130+ MPGe.
- They're the same underlying data, just rotated. mi/kWh is the most intuitive for daily use.
The conversions
Worked example
An EV that gets 3.5 mi/kWh uses 100 ÷ 3.5 = 28.6 kWh per 100 miles, which is 3.5 × 33.7 = 118 MPGe.
Convert any value with the MPGe & Efficiency Converter.
When to use each unit
- mi/kWh — daily driving, range planning, trip math. Most intuitive for “how far can I go.”
- kWh/100mi — comparing efficiency between EVs. Like L/100km in Europe — lower wins.
- MPGe — comparing an EV to a gas car. Required by the EPA on US window stickers.
Typical numbers across the market
| Vehicle (example) | mi/kWh | kWh/100mi | MPGe |
|---|---|---|---|
| Hyundai Ioniq 6 (efficient) | 4.0 | 25 | 134 |
| Tesla Model 3 RWD | 4.0 | 25 | 132 |
| Tesla Model Y Long Range | 3.6 | 28 | 121 |
| Hyundai Ioniq 5 / Kia EV6 (typical) | 3.4 | 29 | 114 |
| Mid-size SUV EV (typical) | 3.0–3.3 | 30–33 | 100–110 |
| Ford F-150 Lightning | 2.5 | 40 | 85 |
| Hummer EV (extreme) | 1.5–1.8 | 55–65 | 50–60 |
Why MPGe exists
EPA mandate. MPGe lets buyers directly compare an EV to a gas car. The math: 1 gallon of gasoline contains roughly 33.7 kWh of energy, so if an EV uses 1 kWh per 33.7 miles, it would be 1 MPGe.
A 132 MPGe EV uses about 132 ÷ 25 = 5.3× less energy per mile than a 25 MPG gas car. That's the heart of why EVs are cheaper to drive even when electricity isn't.
What EPA efficiency doesn't include
EPA efficiency comes from a standardized lab cycle. Real-world driving often produces lower numbers because of factors EPA doesn't fully capture:
- Cold weather: range drops 25–40% in winter. See the cold-weather guide.
- Highway speeds: 15–25% lower than EPA at 70+ mph. Run the math.
- Cabin heating: 3–5 kW continuous draw — significant on short cold trips.
- Roof boxes and big loads: 10–20% efficiency hit.
When estimating real-world cost or range, knock 10–20% off the EPA-rated efficiency for mixed driving, or 25–40% for cold winters and steady highway speeds.
The intuitive frame
For everyday math, mi/kWh wins. It's the easiest to use:
- Range from full charge: Battery kWh × mi/kWh.
- Cost per mile: Electricity rate ÷ mi/kWh.
- Daily energy use: Daily miles ÷ mi/kWh.
Memorize that your car is, say, “3.5 mi/kWh in summer” and most other numbers fall out from that. The window-sticker MPGe is for marketing; mi/kWh is for living with the car.
Quick tools
- MPGe & Efficiency Converter — convert between all three units
- EV Range Calculator — range from battery + efficiency
- EV Cost Per Mile Calculator — running cost from efficiency + rate
- EV Daily Energy Need — daily kWh from your driving
Related reading
- EV range in cold weather — what knocks mi/kWh down most
- EV road trip planning — highway efficiency at scale
- AWD vs RWD EV — the AWD efficiency penalty quantified
- EV vs hybrid vs PHEV — how each compares on efficiency
- Should you buy an EV in 2026?