Extreme weather is sucking the life from your electric car

As more affordable and longer-range electric cars hit the market, the long-predicted shift to battery-powered transportation seems poised to actually happen. But a serious challenge remains: battery-sucking cold weather.

New research from AAA reveals that when the mercury dips to 20 degrees Fahrenheit, the average driving range of an electric car decreases by 41 percent. When colder temperatures hit, EV owners have the same instinct as their internal combustion engine-driving brethren, which is to crank up the heat as high as it will go. This puts a serious strain on an EV’s battery, reducing the overall range and increasing the need to charge more often to minimize the chance of being stranded by a dead battery.

“The appeal of electric vehicles continues to grow since a greater variety of designs and options with increased range have come onto the market,” said Greg Brannon, AAA’s director of Automotive Engineering and Industry Relations, in a statement. “As long as drivers understand that there are limitations when operating electric vehicles in more extreme climates, they are less likely to be caught off guard by an unexpected drop in driving range.”

EV owners discovered this during the recent cold snap that hit central US and Canada. As temperatures plunged, owners of Chevy Bolts and Tesla Model 3s told CNBC they were seeing at most 50 percent less range in their vehicles.

Extreme heat is also a drag on electric vehicles. When outside temperatures heat up to 95 degrees Fahrenheit and air conditioning is used inside the vehicle, driving ranges can decrease by 17 percent, AAA reports. Extreme temperatures certainly play a role in diminishing driving range, but the use of the vehicle’s heating, ventilation, and air conditioning (HVAC) system in these conditions — particularly the heat — has by far the greatest effect.

The problem is that, unlike a car with an internal combustion engine that can warm the cabin with waste heat, EVs have to tap into their batteries to power the climate control system.

Less battery power means more charging, which increases the cost to operate the vehicle. AAA’s study found that the use of heat when it’s 20 degrees Fahrenheit outside adds almost $25 more for every 1,000 miles compared to the cost of combined urban and highway driving at a balmy 75 degrees Fahrenheit.

AAA tested five electric vehicles — the BMW i3, Chevy Bolt, Nissan Leaf, Tesla Model S, and Volkswagen e-Golf — all with a minimum EPA-estimated driving range of 100 miles. Real-world driving conditions were simulated using a dynamometer, which is essentially a giant treadmill for cars, in a closed testing cell where ambient temperature could be tightly controlled.

To determine the effects on driving range, scenarios for cold and hot weather conditions — both when using HVAC and not — were compared to those of driving with a normal outside temperature. Surprisingly, AAA found the impact on range was pretty much uniform among the cars tested.

EV manufacturers will have to find a way to communicate the effects of extreme weather to customer as they push to increase their sales market. In the meantime, owners can take some steps to help mitigate the effect of extreme heat and cold on their vehicles, AAA says. Take some time to pre-heat or pre-cool the car while its still hooked up to a charger. And plan ahead for frequent stops to charge if you’re going on a longer trip, so you don’t get caught on the side of the road with a dead battery.

Update February 11th, 9:55AM ET: In a statement, a Tesla spokesperson disputed AAA’s findings: “Based on real-world data from our fleet, which includes millions of long trips taken by real Model S customers, we know with certainty that, even when using heating and air conditioning, the average Model S customer doesn’t experience anywhere near that decrease in range at 20 degrees Fahrenheit, and the decrease in range at 95 degrees Fahrenheit is roughly 1 percent.”