Most EV owners notice the same pattern after a few motorway trips. The battery percentage falls faster than it did on the commute, yet the cabin feels calm, the car feels planted, and the speed seems reasonable. The disconnect comes from how easily a smooth motorway run hides a large aerodynamic penalty.
On paper, the shift from 98 km/h to 118 km/h does not look dramatic. In practice, that extra pace can remove 30 to 40 kilometres from a medium-length travel leg, especially when the weather is cool and the car is carrying luggage. The loss rarely appears as one obvious event. It arrives as a steady increase in energy draw that the driver only notices once the next charging stop suddenly becomes mandatory.
1. Why speed matters more than drivers expect
Aerodynamic drag rises quickly as speed increases. That is not new information, yet many drivers carry over habits from combustion cars, where a brief rise in consumption feels tolerable because refuelling is fast and stations are dense. In an EV, the consequence is different. Higher speed not only reduces range, it compresses your buffer around charger availability.
I reviewed trip logs from 183 planning sessions submitted by readers this winter. The most common forecasting error was not temperature, tyre pressure, or cabin heating. It was the assumption that a car consuming 18.4 kWh per 100 kilometres at mixed pace would stay close to that figure during two hours of motorway driving. It seldom does.
- Higher sustained speed raises aerodynamic demand disproportionately.
- Cool weather adds cabin and battery conditioning load.
- Headwinds behave like invisible speed increases.
- Late charger decisions reduce options if one site is busy or offline.
- A low arrival buffer turns a small forecasting miss into a stressful reroute.
2. The hidden cost is not only energy
Drivers often frame this issue as a simple efficiency trade-off. The real cost is operational. If you arrive with 6% instead of 14%, you may need to accept the first available charger rather than the best one. That can mean a slower unit, a queue, or a detour into a retail site that was never part of the plan.
Motorway pace also affects charging curve strategy. Arriving warmer and lower can be useful if the charger works and the queue is empty. If either condition fails, the supposed time gain from driving faster disappears. What looked like a confident push down the road becomes a slower journey overall because the charging leg was chosen under pressure.
3. A better planning method
The cleanest fix is simple. Build the plan around recent motorway consumption, then preserve a real reserve. If you do not have enough recent data, raise your usual mixed-driving figure by a disciplined margin instead of choosing a hopeful number. The difference may feel pessimistic at the start. It usually feels realistic by the time you reach the next charger.
For a modern crossover with a usable pack around 74 kWh, I generally advise plotting one route at normal pace and a second at a motorway pace you know you might slip into. If the second plan forces a stop 35 kilometres earlier, use that as the operative route. You can always arrive with extra charge. You cannot spend a reserve you never truly had.
Drivers do not need to travel slowly. They need to understand that speed buys time only when the charging plan remains intact. On a reliable corridor in mild weather, the trade can make sense. In winter, on a busy weekend, or on a route with one critical site, the prudent pace is often the faster decision when the entire trip is measured from departure to final arrival.