Energy & Environment

Wise Driving Tips for EVs

The slower an EV is driven, the more efficient it is. So, a 50-mile range at 55 mph extends to a 100-mile range at 35 mph. Although it is seldom safe to travel this slowly on a road, being aware that the range grows with conservative driving is handy when you need it.

Manufacturer specifications give both a top speed and a maximum range for their electric vehicles. A "rule of thirds" applied to these two numbers helps give an idea of what speed yields the best range. At top speed, the vehicle's range is one-third of the vehicle's maximum range. On a full battery charge, an EV with a top speed of 75 mph and a maximum range of 120 miles will travel about 40 miles at 75 mph; at 25 mph, its range stretches to 120 miles.

Coasting is another mileage-stretching technique. In a vehicle powered by an engine, removing your foot from the accelerator pedal engages a feature called compressive braking, which slows the vehicle and consumes fuel. The same action in an EV without regenerative braking or with it switched off effectively shuts down power to the electric motor, and the EV's own momentum freely spins the motor via the wheels and drive train. Experienced owners use the coasting effect of an EV to great advantage. One way is to simply bring the vehicle over the posted speed by a few miles, then remove your foot from the accelerator pedal. The vehicle coasts, slowed only by tire and wind resistance. Once the speedometer shows that the vehicle has dropped 4 mph below the initial speed, the accelerator is pushed to bring the vehicle back up to the initial speed. Any time the vehicle is coasting, it is not consuming any power, which adds many miles to the vehicle's overall range. A driver who is attentive to traffic, stop signs and traffic signals may allow the EV to coast down from speed to avoid braking. To get the same effect with a car using an engine—slipping the transmission into neutral and shutting down the engine—is hazardous.