EV units
MPGe explained
MPGe means miles per gallon of gasoline-equivalent. It is the US EPA’s way of putting electric vehicles on the same label scale as petrol cars. It is not a liquid-fuel measurement, and it is not the same as the mi/kWh figure shown on the car’s energy display.
The key number: 33.7 kWh
The EPA uses 33.7 kWh as the energy equivalent of one US gallon of gasoline. A vehicle that travels 150 miles on 33.7 kWh has an MPGe of 150. The equivalent efficiency is about 4.45 miles per kWh.
MPGe = mi/kWh × 33.7 mi/kWh = MPGe ÷ 33.7 150 MPGe ÷ 33.7 = 4.451 mi/kWh 100 ÷ 4.451 = 22.47 kWh/100 mi 22.47 ÷ 1.609344 = 13.96 kWh/100 km
MPGe already includes charging losses
This is the part most comparisons miss. EPA’s MPGe and kWh/100 miles are based on energy measured at the outlet, not energy delivered to the battery. The rating assumes Level 2 AC charging and accounts for losses in the charging cable and the vehicle’s onboard charger. It is an outlet-to-wheel figure.
A dashboard mi/kWh figure is usually battery-side: it describes how far the car went on energy that was already in the battery. If you take an EPA-derived mi/kWh and then add 10% charging loss again, you double-count the loss.
Do not mix the two bases
MPGe to the units people actually use
| MPGe | mi/kWh (outlet) | kWh/100 mi | kWh/100 km |
|---|---|---|---|
| 100 | 2.967 | 33.7 | 20.94 |
| 120 | 3.561 | 28.08 | 17.45 |
| 130 | 3.858 | 25.92 | 16.11 |
| 150 | 4.451 | 22.47 | 13.96 |
| 180 | 5.341 | 18.72 | 11.63 |
How to estimate cost from MPGe
Convert MPGe to energy per mile, then multiply by the price of electricity. In the US:
kWh per mile = 33.7 ÷ MPGe cost per mile = (33.7 ÷ MPGe) × dollars per kWh 150 MPGe at $0.17/kWh: 33.7 ÷ 150 = 0.2247 kWh/mile 0.2247 × $0.17 = $0.0382/mile
In the UK, use pence per kWh and divide by 100 to get pounds. In Europe, use kWh per 100 km and euros per kWh directly.
The result is an energy-cost estimate. It does not include charging subscriptions, parking, idle fees, home-charger installation, road tax, insurance or maintenance.
What MPGe does not tell you
- It is not a real liquid-fuel consumption figure.
- It does not guarantee real-world range or efficiency.
- It does not include the cost of electricity; prices vary by tariff and location.
- It does not include cabin heating or cooling losses in extreme temperatures.
- It is a US regulatory label. A WLTP or other market figure uses a different test.
MPGe vs MPG: why the ratio does not apply
You cannot convert MPGe to MPG using the UK/US gallon ratio. MPGe is an energy equivalence for electricity; MPG is a liquid-fuel economy. The two can be placed on a comparable energy basis, but they are not the same physical measurement. For cost, use the price of each energy carrier rather than the label number alone.
Convert an EV efficiency figure
The converter handles MPGe, mi/kWh, kWh/100 mi and kWh/100 km, and labels the basis.
Open the efficiency converterSources
- US EPA — fuel economy and EV range testing — Explains MPGe and that EPA values include charging losses.
- fueleconomy.gov — understanding the EV label — How MPGe and kWh/100 miles appear on US labels.
- EPA — EV and PHEV test procedure — Technical basis for recharge energy and the 33.705 kWh equivalence factor.
Page last reviewed: . Formulas are covered by automated tests. Prices are inputs, not live data.