- Apply 0.95 in town, 0.85 on a 90 km/h road and 0.70 on a 130 km/h motorway in mild weather.
- In winter, drop to 0.75, 0.65 and 0.55 respectively.
- Speed costs range quadratically: doubling speed quadruples aerodynamic drag.
- A 10 % buffer plus a 20 % reserve is the safe way to plan a long trip.
What WLTP actually measures
The Worldwide Harmonised Light vehicles Test Procedure replaced NEDC in 2017. It is a 30-minute laboratory cycle divided into four phases with a top speed of 131 km/h, an average of 46 km/h, and a total distance of 23.3 km. Cabin climate control is switched off, the battery is fully charged at the start, and the ambient temperature is 23 °C.
The result is reproducible and comparable between cars. It is not a forecast. Real consumption depends on speed, temperature, wind, rain, elevation, load, tyres and driving style — variables the cycle deliberately removes.
The conversion factors we use
From comparative measurements and on-road tests, these factors give a useful estimate for a modern electric car:
| Use case | Mild weather (15–25 °C) | Winter (0 °C, heating on) |
|---|---|---|
| City and suburban | 0.95 | 0.75 |
| Rural road, 80–110 km/h | 0.85 | 0.65 |
| Motorway, 130 km/h | 0.70 | 0.55 |
A car rated at 500 km WLTP therefore delivers:
- about 475 km in town in summer;
- about 425 km on a rural road;
- about 350 km at 130 km/h;
- about 275 km on a winter motorway.
These are averages. A large SUV with a poor drag coefficient will do worse on the motorway; a heat pump, a pre-conditioned battery and a modest right foot will do better.
Why speed costs so much
Aerodynamic drag is proportional to the square of speed, and the power needed to overcome it to the cube. At 130 km/h, a typical electric car spends more than 60 % of its energy pushing air. That is why the difference between 110 and 130 km/h is worth 15–20 % of range, while the difference between 70 and 90 km/h is worth only 5–8 %.
Practical consequence: on a long trip, driving at 115 km/h instead of 130 km/h often saves more time than it costs, because it can remove one charging stop.
Winter: where the range really goes
Two effects combine. The battery’s internal resistance rises in the cold, which reduces usable capacity by 10–20 %, and the cabin heater draws 3–5 kW. On a 20 kWh/100 km motorway consumption, that heater alone represents 15–25 %.
What helps:
- A heat pump, which moves heat rather than generating it, cutting the heating penalty roughly in half.
- Pre-conditioning while plugged in, so the cabin and battery are warm before departure.
- Seat and steering-wheel heating, which warm the occupant with far less energy than the whole cabin.
- Battery pre-conditioning before a fast charger, which restores charging speed.
How to plan a long trip
A simple, reliable method:
- Take the WLTP figure and apply 0.70 for a motorway trip in mild weather, 0.55 in winter.
- Subtract a 10 % buffer for wind, rain and detours.
- Plan to arrive at each charger with 15–20 % remaining.
- Target chargers 150 kW or above, and identify a backup charger 30–50 km further on.
Example: a 600 km WLTP car in winter gives about 330 km of realistic motorway range. With a 20 % reserve, that is roughly 260 km between stops — comfortable, and enough to skip an unreliable charger.
Reading consumption figures correctly
Consumption is quoted in kWh/100 km. To convert to cost, multiply by your electricity price:
- 18 kWh/100 km at €0.18/kWh = €3.24 per 100 km.
- The same car on a €0.60/kWh fast charger = €10.80 per 100 km.
Beware of “WLTP consumption” in brochures: it is measured on the same optimistic cycle. Real consumption is typically 15–25 % higher in summer and 30–45 % higher in winter.
The 10 % rule for battery health
Charging losses, vampire drain and battery preconditioning all consume energy that never reaches the wheels. As a rule of thumb, add 10 % to the energy you think you need, both for cost estimates and for trip planning. It is a small margin that prevents most unpleasant surprises.
Frequently asked questions
Why is WLTP range so optimistic?
The WLTP cycle runs in a laboratory at 23 °C, with no wind, no rain, no elevation change, no heating or air conditioning, and a gentle average speed of 46 km/h. It is a comparison tool between cars, not a prediction of your driving.
How much range do I lose at 130 km/h?
About 30 % compared with the WLTP figure in mild weather, and up to 45 % in winter. Aerodynamic drag grows with the square of speed, so the last 20 km/h cost far more than the first 100.
Does air conditioning really reduce range?
Yes, by 5–10 % in summer. Heating is far more costly: a resistive heater can draw 3–5 kW, which is 15–25 % of consumption on a cold motorway run. A heat pump cuts that penalty by roughly half.
How accurate is the range estimator in the car?
It uses recent consumption, so it adapts within 10–20 km. Treat it as reliable in steady conditions, but add a safety margin before a mountain pass or a fast motorway section.