Recent reports described people stranded for up to 19 hours on a Virginia highway in freezing weather during a winter storm. To stay warm, people ran their cars’ engines, heating their cabin and protecting against hypothermia. The fuel gauge moves ever so slowly toward “empty,” with occupants assured of a reasonable number of hours of comfort before the situation becomes unsafe. And, while it’s possible to run out of fuel in a situation like this, it’s rare that traffic jams last long enough for fuel endurance to be of grave concern.
As the adoption of electric vehicles expands, the variety of climates and geographies where they are driven increases accordingly. Gone are the days of EVs being exclusive to sunny California! Many are aware of the quantifiable limitations of an EV’s range in cold weather (if not, check out our report on the truth about winter EV range loss). But what about the safety and endurance of an EV in hazardous conditions like a white-out? What exactly happens when an EV gets stuck in a winter storm – and can it keep its occupants safely warm for as long as an internal combustion engine vehicle?
There are numerous misconceptions abound about how long you can “survive” a winter storm in a stranded EV, with most time estimates being drastically underestimated. But not to worry, we have battery science on our side!
First, here are a few points of reference about gasoline cars as they idle in cold weather:
The first concern about idling in cold weather is moot in an EV. There are no tailpipe emissions to worry about; an electric car’s heater can be safely run regardless of fresh air ventilation.
The second point is largely a commonality between gas and electric cars. The amount of time you can sit in a car with the heat on is determined by how much fuel is in your tank or by the battery’s state of charge. However, unlike in the gas car, it is not common or practical to recharge an EV while stranded. However, mobile chargers and emergency batteries will grow in popularity as EVs become more common.
For the third point, given the enormous range of fuel efficiency and tank sizes on gas cars, it’s hard to nail down an exact figure for how long one can idle in cold weather. We’re using 30 hours as a baseline, assuming a full tank of gas in an average ICE vehicle.
Lastly, while a gas vehicle does generate its cabin heat through a very inefficient process, the same is true for most electric vehicles. In a stationary EV, there is little waste heat, so cabin heat is generated by heating up resistive elements, drive stators, or through heated seats or steering wheels. This heat also costs energy, and figuring out exactly how much it uses determines how long an EV can keep occupants warm.
Let’s assume we have an average EV as per 2022 stats: around 250 miles of range powered by a battery with around 70 kilowatt-hours of capacity. There are five variables that affect how long you can heat an EV while sitting, in rough order from most important to least important:
How does this all play out practically? Let’s take for example an EV with a resistive heater, like the Volkswagen e-Golf. It is a small car with a small battery, and a small cabin to heat. Because of its resistive heating elements, all heat generated for the cabin costs the same regardless of whether or not the vehicle is moving. Drivers report approximately 1.5-2.5 kW of heater draw in outside temperatures from 35 to 15 degrees Fahrenheit. With 50% charge on a 32kWh battery, that translates to between 6.5-10.5 hours of heat on a 15-35 degree day; double that on a full charge.
But what about a modern EV with a bigger battery and better heating options, such as heated seats?
Enter the Tesla Model 3. For 2021, Tesla switched from resistive heating to a heat pump. Drivers report greatly improved efficiency when it comes to heating their cars. One user slept in his Model 3 and ran metrics on it overnight in sub-freezing weather, finding the battery consumed 1.36kW per hour, on average. For a Tesla with a 80kWh battery, this means you could sit in your Tesla nice and toasty for almost 59 hours on a full charge, or about 29 hours on a half charge.
In fact, while writing this post, I decided to run a quick test on my own Model 3. Although I am in California where the temperatures aren't as cold as the Northeast, I blasted the heat in my parked car for 30 minutes. I set the temperature to "hi," which is the only temperature setting above 81 degrees, and boy - was it warm in there! After running for half an hour, my battery percentage declined from 88% to 85%, indicating that I used 3% charge over 30 minutes to make my car uncomfortably warm. At this rate, 6% an hour, I would still get at least 12 hours of heat, and honestly, no one would want it to be that warm for that long!
Starting the experiment at 88% battery capacityTo conclude, modern EVs with average battery packs offer cold weather heating endurance equaling or exceeding that of average gasoline cars, with the added benefit of not needing to worry about carbon monoxide poisoning. For some, this ability may come as an added luxury. For example, drivers report using their EVs for camping, readily using the heat all night without compromising too much range for the next leg of their trip.
Do you have a story to tell about using your EV in cold weather situations? We’d love to hear! Get in contact with us.
With the popularity of many electric cars, more and more people are replacing their traditional cars with electric cars.
Conventional car can use the thermal energy by the engine work to provide heat to the cab when the temperature is low in winter.
And the electric car’s electric motor cannot produce enough thermal energy to heat the cab.
Also, in winter, the battery chemistry is not active and the battery power cannot be fully utilized because of the low temperature. electric car owners also need to heat the battery to raise its temperature in order to make full use of the battery’s electrical power.
According to these factors above, electric cars will need thermal management system more. And electric car heater is one of the very important parts of electric cars.