How your range is worked out
Why the number moves with the hills, the weather and your right foot — and why that is the point.
6 minute read
Most range figures are one number: a manufacturer’s efficiency claim multiplied by your battery. That number is right roughly never, because it describes a car on a test cycle rather than your car on the A1 in February.
WayEV works it out from physics instead. For every stretch of road it asks what your specific car has to overcome, and adds up the energy that takes.
What actually drains the battery
Air resistance. The dominant cost at speed, and the reason motorway driving is so much less efficient than A-roads. Drag rises with the square of speed, and the power needed to overcome it with the cube — so 80 mph is not 10% worse than 70, it is closer to 25%. This is calculated from your car’s frontal area and drag coefficient, which is why a saloon and an SUV with the same battery get different plans.
Rolling resistance. Roughly constant with speed and proportional to weight. It dominates at low speeds and is why a heavy car is thirsty around town.
Gradient. We sample the elevation along your actual route, not the straight line. Climbing costs energy in direct proportion to weight and height gained. Descending gives some of it back through regeneration — but not all of it, so a route over a hill costs more than the flat one even though you end up at the same height.
Heating, cooling and everything else. A more or less fixed drain that matters most when you are moving slowly, because it is measured in time rather than distance. An hour in traffic costs roughly the same auxiliary energy as an hour at 70.
Why winter is worse
Two separate things happen, and they compound. A cold battery is chemically less willing, so you get less usable energy out of the same charge and it accepts charge more slowly when you stop. And cabin heating is expensive in a way it simply is not in a petrol car, where the engine produces waste heat for free.
We pull the actual forecast along your route and account for both, along with wind. A headwind is aerodynamic drag by another name, and a stiff one costs real range — which is why the same journey can produce a different plan on two consecutive days.
Why it disagrees with your car
Your dashboard range is usually a rolling average of recent driving projected forward. It is reasonable on a steady commute and badly wrong the moment conditions change, because it has no idea there is a hill or a headwind coming.
Ours can be wrong too — but it is wrong about the future rather than assuming the future looks like the past.
It gets better the more you drive
Two cars of the same model are not identical. Battery health, tyres, a roof box, and whether you actually drive at 70 all shift the numbers.
So we compare predictions against what really happened on your journeys and adjust to your car. If you consistently use less than predicted, the plans move towards you rather than staying stubbornly generic.
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