Why are electric cars less efficient on the motorway?

All cars, whether powered by an electric motor, a combustion engine or a hybrid system, are most efficient when driven at a steady speed. Saving energy is all about careful use of the throttle. 

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Mercedes-Benz EQC

Heavy application of the accelerator pedal plays havoc with fuel or electricity consumption, even on electric cars that regain power via regeneration when braking.

However, motorway driving, even at a steady speed, can seriously diminish your electric car’s range if you don’t approach it correctly.

Driving an EV on the motorway

Any journey on UK motorways soon illustrates how the 70mph limit is regarded by many as the minimum speed they should drive.

Anecdotally, though, speeds on motorways seem to be dropping, with more drivers sticking to the limit. One likely reason for this is fuel economy.

It’s largely down to aerodynamics: the faster you drive, the more the wind resistance – or aerodynamic drag – works against you. And drag increases exponentially with speed.

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Audi e-tron

If you drive at a constant 70mph on a motorway, you should, theoretically, get close to the manufacturer’s stated range for the battery.

Drive at 75mph instead, though, and range might drop by between five and 10 percent. At 80mph, it’s around 10 to 15 percent less than at 70mph.

Not surprisingly, there are big efficiency gains from cruising at lower speeds. At a steady 60mph, you’ll see a significant range improvement – and you may be surprised at how little difference it makes to your overall journey time.

That said, driving at 60mph in the inside lane of the motorway, dicing with 32-tonne trucks, can be a daunting experience.

Does speed really matter?

As with any car, the way you drive makes a difference to how far you can travel before recharging.

While electric cars outshine conventional vehicles in urban environments with superior efficiency, on motorways it’s more of a level playing field.

So yes, speed really does matter, and if you can keep your head and cruise at 70mph (or less) on the motorway, you’ll get the best range.

Driving at lower speeds could also mean fewer stops for charging on your trip. Truly a case of the tortoise and the hare.

ALSO READ:

How do you drive an electric car?

Can you trust the quoted range of electric cars?

What happens if an electric car runs out of battery charge?

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