By EV Charge Cost Editorial Team. Published September 28, 2026, updated October 26, 2026.
Four ways to say the same thing
EV efficiency shows up in several units depending on where you look:
- kWh per 100 miles: the EPA label figure; lower is better.
- kWh per mile or Wh per mile: the same idea per single mile; lower is better.
- Miles per kWh: common on car dashboards and apps; higher is better.
- MPGe: miles per 33.7 kWh; higher is better. See MPGe explained.
The formulas
- kWh per mile = kWh per 100 miles ÷ 100
- Wh per mile = kWh per mile × 1,000
- Miles per kWh = 1 ÷ kWh per mile = 100 ÷ kWh per 100 miles
- MPGe = 33.7 × miles per kWh = 3,370 ÷ kWh per 100 miles
- Cost per mile = kWh per mile × price per kWh
Conversion table
Cost per mile uses the U.S. average residential price of 18.16¢/kWh (EIA, August 2026).
| kWh/100 mi | kWh/mi | Wh/mi | mi/kWh | MPGe | ¢ per mile |
|---|---|---|---|---|---|
| 24 | 0.24 | 240 | 4.17 | 140 | 4.4 |
| 28 | 0.28 | 280 | 3.57 | 120 | 5.1 |
| 32 | 0.32 | 320 | 3.13 | 105 | 5.8 |
| 36 | 0.36 | 360 | 2.78 | 94 | 6.5 |
| 40 | 0.40 | 400 | 2.50 | 84 | 7.3 |
| 45 | 0.45 | 450 | 2.22 | 75 | 8.2 |
| 50 | 0.50 | 500 | 2.00 | 67 | 9.1 |
| 60 | 0.60 | 600 | 1.67 | 56 | 10.9 |
The most efficient model in our data, Tesla Model 3, is rated 26.4 kWh/100 mi (3.79 mi/kWh). The least efficient, GMC Hummer EV, is 70.3 kWh/100 mi (1.42 mi/kWh).
Worked examples
- From the EPA label. A car rated 33.5 kWh/100 mi uses 0.335 kWh per mile and goes 2.99 miles per kWh. A 40-mile round trip needs 13.4 kWh, about $2.43 at 18.16¢/kWh.
- From a dashboard reading. If your car shows 3.5 mi/kWh, that is 1 ÷ 3.5 = 0.286 kWh per mile, or 28.6 kWh per 100 miles (before charging losses).
- From Wh per mile. 250 Wh/mi is 0.25 kWh per mile, 25 kWh per 100 miles and 4 miles per kWh.
Metric units
Outside the U.S. you will often see kWh per 100 km. Because one mile is 1.609344 km, kWh per 100 km = kWh per 100 miles ÷ 1.609344. A 33.5 kWh/100 mi car is about 20.8 kWh/100 km. To go the other way, multiply by 1.609344. Km per kWh is simply 100 ÷ kWh per 100 km.
Dashboard numbers vs the EPA label
There is one trap. The EPA figure is measured at the wall, so it includes energy lost while charging. A car's trip computer usually measures energy leaving the battery, which excludes those losses. The dashboard number therefore tends to look better than what you pay for.
As an illustration, if 10% of the energy drawn from the wall were lost in charging, a dashboard reading of 4.0 mi/kWh would correspond to about 3.60 miles per kWh bought, or 27.8 kWh/100 mi from the wall. Real losses vary with charger level, temperature and the car. See EV charging losses.
Turning your own number into a cost
- Read miles per kWh from your car's trip computer over a few weeks.
- Convert: kWh per 100 miles = 100 ÷ mi/kWh. Adjust for charging losses if you want a wall-based figure.
- Multiply by your price per kWh. At 18.16¢/kWh, every 1 kWh per 100 miles costs $0.18 per 100 miles.
Whichever unit you start from, keep one rule in mind: for cost, convert to energy per distance (kWh per mile or per 100 miles), because that is what multiplies cleanly by a price. Distance-per-energy units such as mi/kWh and MPGe are fine for comparing cars but awkward for budgeting.
Or enter the kWh/100 mi value directly in the charging cost calculator. For a wall-based figure from your own records, divide the kWh your charger reports by the miles driven.