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.
The engine in an electric car does not generate heat, so EVs must use specially designed heating and cooling systems. Maintaining the right temperature in the cabin in winter is not only a matter of driving comfort, but above all safety, since the windows must not be fogged up or frosted. You should know how an air conditioning system works in order to use it optimally.
The air conditioning system works in conjunction with the car's heating system and is responsible not only for cooling the interior in summer, but also for warm air in winter. The common element of both systems is the refrigerant, which, depending on the mode of operation, receives heat from the heater or is cooled in the radiator. Circulation of the refrigerant at as high pressure as 17 bar is forced by a compressor driven by a multi-ribbed belt, which in turn transmits the drive from a pulley on the engine's crankshaft. In the cooling system, the refrigerant enters a condenser cooled by a momentum of air or a fan and changes from a gaseous to a liquid state. From there, the liquid is transported to a dehumidifier and then an expansion valve, where it transforms into a -4 °C gas. It then cools the evaporator, through which the air blown into the cabin flows. In a heating mode, on the other hand, the same refrigerant takes heat from the engine and transfers it to the heater, which heats the air flowing through it. An engine-driven fan is responsible for blowing cooled or heated air into the cabin. Knowing how air conditioning works in a combustion car, it is easier to understand the principle of this system in electric cars.
The electric motor does not emit heat, but this does not mean there is no heating in the car. The mechanism of operation of cooling and heating systems in electric cars is actually not very different from those found in combustion cars. The main difference is the power source of the compressor. It is not the crankshaft in this case, but the batteries for electric cars. Compressors in EVs have their own built-in electric motor, an inverter that converts direct current drawn from the battery into AC, and a separator that separates the compressor oil from the refrigerant. Among the advantages of the solution, where the compressor is powered directly from the battery, is the ability to run the air conditioner while parked, with the engine off. In new electric cars you can also find a heating system based on a heat pump, which somewhat resembles the split air conditioners used to heat buildings. The air-to-air heat pump can operate in both heating and cooling modes. In a heating mode, the warm air it produces is directly blown into the cabin, while in cooling mode it goes to a condenser, followed by a dehumidifier, expansion valve and evaporator. The heat pump is also powered by a lithium-ion battery using an inverter.
Turning on the car's heating increases the energy demand for the compressor, which in the case of electric cars is associated with faster battery drainage. Given the small number of fast chargers and the extended battery charging time in cold weather, BEVs seem like a good option only for city trips, and that's provided you have your own charging point at home. However, there are ways to reduce the electricity consumption of electric vehicles and hybrid cars in winter. First, preheat the car's interior even before hitting the road. It's best to plug it into a charger, or if that's not possible, set it up in a sunny location. Secondly, while driving, it is a good idea to turn on the economy mode that reduces the energy consumption of individual systems to a minimum. If the car is equipped with heated seats and steering wheel, you can set the interior temperature to the lowest level or opt for no heating in the car. However, energy consumption for heating the interior depends not only on skillful energy management, driving speed and battery operating temperature, but also on the type of heating and proper insulation of the car's interior.
There are several different types of heating in electric cars, but the most common is an electric heater connected to a blower. Although the power of such heaters is mostly small, as low as 2 to 4 kW, in negative temperatures they greatly accelerate the process of battery drainage. It has even been tested in practice how long an electric car battery lasts in winter. Tests conducted by the American Automotive Association showed that in temperature conditions below -7°C, the average range of an electric car drops by up to half compared to optimal conditions of 24°C. This problem does not occur in warm climatic conditions, but in northern Europe or America, for example, where there are sometimes very harsh winters, the use of such heating in the car can make it impossible to travel long distances outside the city.
Heat pump is an increasingly common type of heating in electric cars. By properly compressing and expanding the heating medium, free heat energy drawn from outside can be used to heat the vehicle cabin. Tests in winter conditions have shown that this requires less energy than a traditional system with an electric heater, but only within a certain range of outdoor temperatures. At temperatures between 0 and 10°C, the heat pump is estimated to consume about 1 kW of energy, so it saves 1-2 kW for every hour of operation. At lower temperatures, the situation changes to the disadvantage of the heat pump. It is also often emphasized that the heat pump is a good solution only if the car is used for city driving and has a battery with a relatively small capacity. If the car is to cover longer distances, it is more profitable to invest in a model with a more capacious battery and a system based on a traditional resistance heater.
The High Voltage Heater (HVH) is a device that is small in size and weighs just 2.7 kilograms, yet is very efficient. Unlike heat pumps, this technology is based on a water heating model instead of air heating. It can be used for both maintaining a comfortable temperature in the cabin and preheating or cooling the traction engine. The HVH heater is designed to operate over a wide range of supply voltages from 100 to 450 V, while its maximum heating power is as high as 7 kW. The high efficiency of this solution makes it applicable to large vehicles, such as trucks and buses. The most common application of this technology is electric parking heating of the driver's cabin used in trucks, but it is also successfully used in passenger cars. Automobile design is increasingly combining all of these technologies in various combinations, or using the most comprehensive solutions possible to provide the greatest benefits.
A very important aspect from the point of view of maintaining a comfortable temperature in the vehicle cabin is not only to produce heat or cold efficiently, but also to retain it where it is needed. In this regard, automotive components made of EPP foamed polypropylene, which features excellent thermal insulation, impact and deformation resistance, and minimal weight, are perfectly applicable. Even today, EPP has become a leading material that is widely used by car seat manufacturers. Among other things, it is used to manufacture seat fillings, headrests, armrests or car door panels, and even body components for passive safety. The excellent moldability and electrical properties of this material have also led to its use in the production of batteries for electric cars. Battery components molded from it protect sensitive cells from extreme temperatures, surges and mechanical damage. Thus, they make it possible to increase the range and safety of electric cars in many ways.
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