EV & charging

mi/kWh vs km/kWh: EV efficiency units made simple

By RoadCost Editorial3 min readUpdated 27 October 2026

EV efficiency can be written as mi/kWh, km/kWh, kWh/100 km or kWh/100 mi. They are all related, but they point in different directions. Higher mi/kWh is better; lower kWh/100 km is better.

Quick answer

1 mi/kWh = 1.609 km/kWh. To convert km/kWh to kWh/100 km, divide 100 by km/kWh. For example, 4 mi/kWh is about 6.44 km/kWh, or 15.5 kWh/100 km.

In this guide

1. The conversions
2. Examples
3. Which unit should you use?
Questions

Key takeaways

Higher mi/kWh and km/kWh are better.
Lower kWh/100 km is better.
1 mi/kWh equals 1.609 km/kWh.

The conversions

The mile-to-kilometre conversion is the only distance change. The energy unit stays the same. For consumption, the relationship is inverted.

km/kWh = mi/kWh × 1.609344
kWh/100 km = 100 ÷ km/kWh
kWh/100 km = 100 ÷ (mi/kWh × 1.609344)

Examples

A car at 3 mi/kWh is at about 4.83 km/kWh, or 20.7 kWh/100 km. A car at 5 mi/kWh is at about 8.05 km/kWh, or 12.4 kWh/100 km.

EV efficiency conversions
mi/kWh	km/kWh	kWh/100 km
3.0	4.83	20.7
3.5	5.63	17.8
4.0	6.44	15.5
5.0	8.05	12.4

Which unit should you use?

Use the unit that matches your market and the source of the number. The important part is to convert before comparing. A higher mi/kWh figure is not directly comparable with a kWh/100 km figure without conversion.

Questions

How many km/kWh is 4 mi/kWh?

About 6.44 km/kWh.

Is higher mi/kWh better?

Yes. It means the car travels further on each kilowatt-hour.

How do I convert to kWh/100 km?

Divide 100 by the km/kWh figure. For 4 mi/kWh, that is about 15.5 kWh/100 km.

Sources

US EPA — fuel economy and EV range testing — Explains MPGe and the test basis for EV efficiency.
fueleconomy.gov — understanding the EV label — How MPGe, kWh/100 miles and range appear on US labels.
US DOE Alternative Fuels Data Center — home charging — Home charging equipment, tariffs and practical considerations.
US EPA — electric vehicle myths — Common EV efficiency, emissions and charging questions.
US EIA — electricity data — US electricity prices, generation and sales data.

Try the calculator

Fuel efficiency converter

Convert EV efficiency units alongside MPG and L/100 km.

Related guides

kWh/100 km explained: the EV version of L/100 km

Learn what kWh/100 km means, how to turn it into cost per 100 km, and how it differs from mi/kWh and battery-side efficiency.

EV charging losses explained

Why the electricity you pay for is not all stored in the battery, the charging-loss formula, and how to avoid double counting.

EV vs petrol break-even: how to calculate it

Estimate the annual running-cost saving from an EV and the years needed to recover a purchase-price difference.

A note on prices and rules

This guide explains arithmetic and units. It does not publish live fuel prices, electricity tariffs or changing tax rules. Use your own price and check official sources for anything that changes.

Page last reviewed: 27 October 2026. Formulas are covered by automated tests. Prices are inputs, not live data.