An electric vehicle’s efficiency describes how much electrical energy it uses to travel a given distance. Petrol cars quote litres per 100 kilometres or miles per gallon; EVs quote kilowatt-hours against distance. The better your efficiency, the further each kilowatt-hour of battery carries you — and the less every journey costs.
The two families of EV efficiency units
Every EV efficiency figure belongs to one of two families, and mixing them up is the most common source of confusion:
- Consumption units measure energy per distance: Wh/km, kWh/100km, Wh/mi and kWh/100mi. Like litres per 100km,lower is better.
- Efficiency units measure distance per energy: km/kWh and mi/kWh. Like miles per gallon, higher is better.
Because the families are reciprocals, converting between them inverts the number. A car using 160 Wh/km is the same as 16 kWh/100km, 6.25 km/kWh and about 3.9 mi/kWh — four ways of describing exactly the same drive. Our EV efficiency converter translates between all six units in one step.
What is a good EV efficiency?
As a rule of thumb for mixed real-world driving:
- Under 15 kWh/100km (150 Wh/km, over 4.1 mi/kWh) — excellent. Efficient hatchbacks and saloons in mild weather.
- 15–20 kWh/100km (150–200 Wh/km, 3.1–4.1 mi/kWh) — typical for most modern EVs.
- Over 22 kWh/100km (220 Wh/km, under 2.8 mi/kWh) — large SUVs, vans, winter driving or sustained motorway speeds.
Context matters more than the raw figure: 19 kWh/100km on a freezing January motorway can be more impressive than 15 kWh/100km on a warm city loop. Compare your car against itself across seasons before comparing it against the brochure.
Why your efficiency differs from the official figure
Official ratings come from lab cycles — WLTP in Europe, EPA in North America — run at moderate temperatures and speeds. Real driving adds cold batteries, cabin heating, headwinds, hills, roof boxes and 120 km/h cruising, and each one costs energy. Most drivers see real-world consumption 10–30% above the rating, with winter motorway trips at the top of that range.
How to measure your own EV efficiency
You don’t need any equipment — just your trip computer and battery display:
- Note your state of charge before a trip (or charge to a round 80%).
- Drive normally, then record the ending SOC and distance covered.
- Enter the three numbers into the EV efficiency calculator to get energy used, distance per kWh and consumption in every unit.
Repeat across a few seasons and you’ll build a personal efficiency baseline — the single most useful number for planning trips, which is exactly what our guide to calculating EV range covers next.