Why your car says one range and delivers another
The number on the dash is a prediction based on how you have been driving. Change the conditions and the prediction changes with you.
Three different range numbers get confused constantly, and they are measuring different things.
1. The official figure (WLTP or EPA)
A standardised laboratory test. Its purpose is comparison between cars, not prediction of your journey.
WLTP is generally more optimistic than EPA. Neither reflects a cold motorway run.
Treat it as you would a headline mpg figure: useful for ranking, not for planning.
2. The dash estimate
A rolling prediction, calculated from your recent consumption. Most cars average the last few hundred miles.
This is why it moves around:
- Weeks of gentle town driving → optimistic estimate
- Start a motorway journey → the estimate falls faster than the miles you cover
- The car is not broken; it is learning
Some cars offer a "guess-o-meter" and a flat percentage. The percentage is more honest, because it is not pretending to predict.
3. What you actually get
Determined by the things the other two cannot know:
- Speed — drag rises with the square of it, so motorway pace is disproportionately costly
- Temperature — see winter range
- Elevation — though regeneration returns much of a climb on the way down
- Load — passengers, luggage, a roof box
- Tyre pressure — small, constant, cumulative
The readout worth watching instead
Efficiency: miles per kWh, or kWh per 100 miles.
Unlike range, it is not a prediction. It is a measurement of what just happened, and it is directly comparable between journeys.
Once you know your real figure for a given kind of driving, range becomes simple arithmetic:
usable capacity × your efficiency = real range
A 60 kWh car at 3.5 mi/kWh on a winter motorway run is a 210-mile car, whatever the dash says.
Planning with it
Use percentage plus known efficiency rather than the dash range. It is more stable and it will not surprise you halfway up a motorway.
Our charging cost calculator takes your efficiency figure directly, which is why we ask for it rather than assuming.
In pictures
Common questions
Why does range drop faster than miles driven?
Because the estimate is recalculating. Start a motorway run after weeks of town driving and the car revises its assumption downward as it learns the new consumption.
About the author
ElectraMile EditorialEditorial desk
The ElectraMile editorial team covers charging, running costs and EV ownership for readers in the UK and US.
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