Start with your journey, not the advert’s maximum
Write down the longest routine leg between dependable chargers. Include the return trip if you cannot reliably charge at the destination. Record the intended departure charge and the energy you want left on arrival. A 300 km advertised range does not mean you will normally leave with enough energy to drive 300 km.
Consumption changes with driving conditions. The US Department of Energy identifies temperature, speed, acceleration, load and inclines as relevant factors. Use a consumption observation resembling your route where possible. A mild-weather city average is a poor stand-in for a cold motorway journey.
Calculate the energy window first
Use current usable capacity when you have a defensible measurement. A new-car usable specification is a baseline; a gross capacity figure is a different quantity. Starting charge minus arrival reserve gives the fraction you intend to use.
For an illustrative 54 kWh usable battery, leaving at 80% and retaining 10% gives 54 × (0.80 − 0.10) = 37.8 kWh for driving. Divide that energy by consumption and multiply by 100 when the consumption unit is kWh/100 km. Keep the reserve in the calculation rather than subtracting an arbitrary distance afterwards.
Compare conditions without changing the battery
At 18 kWh/100 km, the 37.8 kWh window gives 210 km. At 23 kWh/100 km, it gives about 164 km. The battery is identical in both scenarios. The roughly 46 km difference comes entirely from consumption.
This is a useful distinction when a dashboard range falls in winter: lower displayed range alone does not measure permanent capacity loss. Change one input at a time to see whether the planning problem comes from capacity, consumption or the charge window.
| Consumption assumption | Planning range | 180 km leg |
|---|---|---|
| 18 kWh/100 km | 210 km | Fits within the assumed energy window |
| 21 kWh/100 km | 180 km | Uses the full planned window; no extra margin beyond the reserve |
| 23 kWh/100 km | About 164 km | Needs a different departure charge or a charging stop |
Work backwards to find the charging requirement
A 180 km leg at 23 kWh/100 km needs 41.4 kWh. In a 54 kWh battery, that uses about 76.7 percentage points of charge. Adding a 10% arrival reserve gives an approximately 86.7% required departure charge under those assumptions.
That is a planning result, not a recommendation to charge every car to the same daily limit. Follow the vehicle’s own charging guidance. If the needed departure charge or charging opportunity is impractical, plan a stop and an alternative station. Include detours and access restrictions when choosing the stop.
Use the right units and avoid counting a penalty twice
Miles per kWh describes distance from one unit of energy; kWh/100 km describes energy needed for a fixed distance. Higher is better for the first unit and lower is better for the second. Convert them before comparing cars. For example, 4 miles/kWh is about 15.53 kWh/100 km.
If you already use measured winter consumption, do not add a second winter penalty merely because it is cold. In EVVerity’s range tool, temperature and driving profile document the scenario; the explicit consumption adjustment changes the arithmetic. The separate winter tool instead applies a chosen range-loss assumption to a normal-weather baseline.
What to record on a useful test drive
Record the route, distance, duration, speed pattern, weather, heating use and consumption unit. Note the charge at departure and arrival, but do not deliberately run the car to empty. A short viewing drive can establish comfort and normal operation while still being unrepresentative of your longest trip.
Use the result to build a range of plausible consumption inputs. The most useful answer is often a condition: “This leg fits if consumption stays below 21 kWh/100 km; otherwise I need to leave with more charge or stop.” That explains the trade-off more clearly than a single maximum-range number.
Put the explanation to work
Use your own vehicle information, check the assumptions and see the calculation.
Real-World Range →EVVerity estimates are informational and are not a substitute for a professional battery diagnostic or pre-purchase vehicle inspection.
Sources & editorial basis
- US Department of Energy — driving conditions and electric range
- US Department of Energy — winter preparation and charging
Source list reviewed 2026-10-26. Additional guidance carries its own review date. Practical checklists and worked examples are EVVerity editorial guidance. Read our methodology.
Related reading
Apply this to a model
Check the model’s battery references, charging equipment and viewing checklist. Match the year and original market to the car you are considering.