Geotab released an interactive analysis, which showed how an EV’s maximum range can change depending on climate and driving behavior.

The chart shows that the optimal temperature to maximize range is 68F for both the sedan (solid orange line) and the light cargo van (dotted orange line).

However, the ideal speed where range is maximized changes with the temperature. For example, at 68F the sedan’s range is maximized at a approximately 19 mph, whereas at 32F the optimal speed is doubled to 37 mph.

"This is the result of a tradeoff between the amount of energy required to overcome drag and the energy needed to keep the vehicle cabin at a comfortable temperature," Geotab's analysis noted. "Faster speeds will get you to your destination more quickly, meaning less total energy spent on HVAC, which is good for range. However, faster speeds also means more energy is needed to overcome drag, which is bad for range."

Geotab added that, due the force of drag is stronger on a van, efficiency peaks at even slower speeds. At an ideal 68F temperature, the most efficient speed is 16 mph. At freezing temperatures, the optimal speed is approximately 25 mph.

In conculsion, Geotab said there isn't one answer to if speed or temparute has the bigger impact on EV range. 

"Generally speaking, speed becomes more dominant at higher speeds, and sticking to the speed limit enroute is the best way to conserve range," the company stated. "If you’re driving a light cargo van or a similarly larger vehicle, you shouldn’t notice much seasonal difference in your vehicle’s range, particularly if your routes are mostly highway driving. The reality is for most fleet applications, today’s EVs can complete their trips on a single charge regardless of speed or temperature."