AAA tested electric vehicles to assess their performance in extreme temperatures. EV batteries operate best between 65 to 75 degrees Fahrenheit, with efficiency dropping in colder or hotter conditions.
Key points
AAA tested electric vehicle performance in extreme temperatures
EV batteries are most efficient between 65 to 75 degrees Fahrenheit
Cold weather reduces battery efficiency and increases energy use
Hot temperatures also negatively impact electric vehicle operation
An electric vehicle charges at an EVgo electric charger in Monrovia, Calif.
An electric vehicle charges at an EVgo electric charger in Monrovia, Calif.
Justin Sullivan/Getty Images
Justin Sullivan/Getty Images
Electric vehicle batteries are a lot like people, in one important respect: They're most comfortable in temperatures around 65 to 75 degrees Fahrenheit.
When the weather gets much colder or hotter than that, a battery works less efficiently. It has to work harder, too, to keep the vehicle's cabin comfortable for its equally picky human occupants.
The result? Electric vehicles can't drive as far or as efficiently in extremely hot or cold weather.
AAA has been testing exactly how big an effect temperatures have on modern EV batteries. In its latest research, shared exclusively with NPR, it found that hot temperatures reduced range by an average of 8.5%. Cold weather cut vehicles' range by a whopping 39%.
Czech energy group hints at combined bid for British Steel and Speciality Steel UK
Czech energy group Sev.en Global Investments is advocating for a single buyer for British Steel and Speciality Steel UK, aiming to create the UK's largest steelmaker. The company plans to invest £100 million and potentially hundreds of millions more in the UK steel industry.
AAA ran similar tests back in 2019 with a different vehicle lineup. Back then, the cold weather hit to range was approximately the same, while the high-temperature range loss was higher, 17%. The different slate of vehicles complicates direct comparison, AAA warns, but does suggest some improvements in how EVs handle the heat.
But not the cold. "There's been a lot of technology changes," says Greg Bannon, the director of automotive engineering at AAA. New battery chemistries; more efficient EV designs; fancier software. But when it comes to winter range performance, "the electric vehicles actually didn't change all that much from back in 2019."
Greg Bannon, the director of automotive engineering at AAA, at the Automotive Research Center in Los Angeles. New battery chemistries; more efficient EV designs; fancier software. But when it comes to winter range performance, “the electric vehicles actually didn't change all that much from back in 2019.”
Greg Bannon, the director of automotive engineering at AAA, at the Automotive Research Center in Los Angeles.
Courtney Theophin/NPR
Courtney Theophin/NPR
These results show that drivers need to be prepared for their real-world range to shrink in the winter — and to a lesser extent, at the height of summer. EVs can still be practical choices in hotter or colder climates, as long as drivers adjust for predictable range loss. "It can be overcome," says Bannon. "But you have to plan for it."
A treadmill in a freezer
AAA conducts these tests at its own expense, part of a slate of research the group does into emerging vehicle technology for the benefit of auto club members. The tests are carried out at its Automotive Research Center in Los Angeles. Specifically, inside the historic headquarters of the Automobile Club of Southern California: a Spanish Revival-style building, all stucco and red tiles, built around a century-old Moreton Bay fig tree, with a courtyard filled with oranges, palm trees and fountains.
It's possibly the most picturesque place for a California driver to get a smog check. (Yes, AAA offers that here.) But it's not, at first glance, a likely spot for testing how vehicles perform in extreme temperatures, especially not on an April day in the mid-60s. (The locals complained about it as "jacket weather.")
The Automotive Research Center in Los Angeles, located inside the historic headquarters of the Automobile Club of Southern California.
Courtney Theophin/NPR
Courtney Theophin/NPR
But tucked away inside this building is a room that's heavily insulated and packed with powerful heaters and coolers. It can be cranked down to 20 degrees Fahrenheit, or up to 95.
Inside, there's enough space for a single vehicle, parked very carefully on top of two giant steel rollers — each of them 4 feet in diameter — that are hidden beneath floor level.
This is a chassis dynamometer, or "dyno" for short. "For lack of a better term, I guess it's kind of like a treadmill for a car," says Megan McKernan, who manages the research center.
For each test, the two rollers are carefully positioned to match up with the wheels of the test vehicle. Then the car is driven right on top of them, making sure the wheels touch nothing else. The vehicle is tied down with heavy, bright-pink chains, so it can't move forward off the "treadmill."
A test vehicle is positioned on a chassis dynamometer. "For lack of a better term, I guess it's kind of like a treadmill for a car," says Megan McKernan.
A test vehicle is positioned on a chassis dynamometer. "For lack of a better term, I guess it's kind of like a treadmill for a car," says Megan McKernan.
Courtney Theophin/NPR
Courtney Theophin/NPR
Now, it's time for Richard Gonzalez to "drive" the vehicle — without actually going anywhere. Once he gets inside and presses the accelerator, the wheels make those giant rollers turn. For hours.
This is about as fun as it sounds. Gonzalez much prefers other parts of his job, like track tests, where AAA evaluates how well cars can, say, automatically brake to avoid pedestrians. But podcasts help pass the time.
The point is to see how far the battery can go, under these controlled conditions, at a certain temperature.
Once the car's battery is drained so much that it can't maintain highway speeds, the test is over. And AAA has a new data point showing how well a certain model's battery can take cold or heat.
A small hit in the summer, a big one in the winter
EVs are not the only kinds of cars that suffer in the cold. AAA also tested hybrids this time around and found a nearly 23% average loss in fuel economy in the 20 degrees F test.
"Internal combustion engine vehicles also lose range in extreme cold weather," points out Ed Kim, the chief analyst with the research group AutoPacific, who was not involved in AAA's research. The Environmental Protection Agency has estimated a 10% to 30% drop in gas vehicle fuel economy in cold weather, depending on the type of trip. "This isn't a problem that's exclusive to EVs. This happens to basically any kind of vehicle when it gets really cold."
A group of electric vehicles are parked in Geiranger, Norway. The country has the highest rate of EV adoption in the world.
Electric vehicles are parked in Geiranger, Norway. The country has the highest rate of EV adoption in the world.
Martin Berry/UCG/Universal Images Group via Getty Images
Martin Berry/UCG/Universal Images Group via Getty Images
But in the U.S., it's a different story. Kim says that EVs have taken off much more in states where temperatures are warm or mild than in the chilly Midwest. State policies and charger availability also play a role, but Kim says fears about winter range — both valid concerns and misinformation-fueled myths — are a factor.
Still, Kim says even with a significant amount of range loss, many drivers in cold-weather regions would still find an EV more than sufficient for their daily needs. "How many people are actually driving more than 200 miles in a day?" he asks rhetorically.
Tips for getting the most from a battery, year-round.
Range loss from extreme temperatures is inevitable, but EV drivers can prepare for it.
First, pick the right vehicle to battle the temperatures where you live. Some are better than others at handling cold or heat. There are several guides; the most fun comes from a Norwegian auto club that does a head-to-head test every year on a wintry mountain.
A little forward planning helps, too, Kim and Bannon both say. For an EV driver who charges at home overnight and has a typical commute, reduced winter range likely won't affect daily driving at all. But if you don't have a home charger or you're going on a long trip, factor range reduction in when you think about when and where you'll charge. And if you're fast-charging, try to do it on a battery that's been warmed up; charging is slower on a cold battery.
Bannon also recommends that drivers start their climate control while their vehicle is still plugged in. "Pre-conditioning" like that means that when you warm up the car's battery and its interior, you pull power from the grid, not your battery. That saves your vehicle's juice for your drive.
McKernan notes that if you have heated or ventilated seats, using those instead of the air conditioning or heater can be a big boost. The AC and heat are a surprisingly big draw on a vehicle's energy.
And keep your tires inflated to the manufacturer-recommended level and drive at moderate speeds. That boosts your vehicle's efficiency no matter whether it runs on gas, a giant battery or both — and no matter the temperature.
