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While it varies by vehicle, blasting an EV heater may cost you between 1,000 and 5,000 watts (1 to 5 kilowatts) of power an hour, depending on how cold it is outside.TOBY MELVILLE/Reuters

We bought a new Chevy Bolt this fall and haven’t driven it in cold weather yet. We’re considering driving to Alberta if we’re allowed on the highways. I know that some EVs can lose range in really cold weather, just like gas cars do. But we’re more worried about staying warm if we’re stranded. Mountain highways get shut down for hours because of weather or crashes. We were stopped for nine hours one year while they cleared an avalanche. It’s not fun in a gas-powered car and we always make sure we had sleeping bags, water and warm clothes. But in an EV, how quickly could we run out of battery power entirely? – Kris, North Vancouver

Whether you’re in an EV or a gas-powered car, make sure you’re topped up on fuel in case you end up stranded, experts said. The closer you are to full, the longer you can run the heat.

“Depending on the state of charge of the battery and how high the heat is cranked, a car like the Chevy Bolt might be able to sustain heat for anywhere from 8 to 40 hours,” Jim Vanderwal, director of climate change programs with the Fraser Basin Council, said in an email. “What this means is that it’s important for an EV driver to plan their route, and identify charging opportunities and stop when needed.”

You might have even more time than that.

Let’s do some math. While it varies by vehicle, blasting an EV heater may cost you between 1,000 and 5,000 watts (1 to 5 kilowatts) of power an hour, depending on how cold it is outside.

“It would be 1 kW around freezing and more in colder situations, like minus 20 degrees Celsius,” Michael Stanyer, program co-ordinator with Plug In BC, said in an email. “Once the cabin is heated, the consumption goes back down to around 1 kW.”

The bigger your battery, the longer you can run the heater.

Most EVs sold now have a battery capacity between 50 and 80 kilowatt hours, Stanyer said.

“A 50 kWh battery would run heat at 1 kW for nearly 50 hours, assuming the car is using a bit of power for other things like the infotainment screen,” Stanyer said.

That’s on a full charge. If that 50 kWh battery is down to 20 per cent, then you might only get ten hours.

The 2021 Bolt has a 65 kWh battery, so you may get up to 65 hours of heat on a full charge.

These numbers are for if you’re running the heater constantly – but you wouldn’t need to do that.

“You don’t want to floor the heater,” said Yves Racette, a consultant who specializes in training automotive technicians about EVs and hybrids. “You just don’t want to freeze – so you can set it to 14 degrees Celsius.”

When an EV isn’t moving, it won’t use power unless you turn on accessories. The heater causes the biggest drain.

If you’re dressed for the cold and have blankets, you may be able to get by for stretches with just the heated seats. They would use less power than the heater, Racette said.

Again, there are a lot of variables. On an older battery, you might lose some capacity – but you’d still have hours of heat.

Of course, you’d want enough power left so you can get to the next charger when traffic starts moving again.

Winter camping in an EV?

Bjorn Nyland, a Norwegian YouTuber, has camped overnight in EVs. While Nyland was camping in a Tesla Model 3 when it was minus 26 degrees Celsius, the heater used 1.95 kW.

Nyland uses insulated window shades to keep heat in the vehicle.

“Big glass panoramic roofs are becoming more common in newer vehicles, so drivers should keep that in mind when they are making an emergency roadside kit,” Plug In BC’s Stanyer said. “Regardless of what powers the vehicle, those [glass] surfaces can be insulated to conserve heat in an emergency.”

So, how does an EV compare to a gas-powered car when it comes to staying warm if you’re stranded?

For the heat to work in a gas car, you’ll have to be idling. How long you can idle depends on the size of the engine and the size of the gas tank.

For instance, a Honda CR-V with a 1.5-litre engine uses 0.9 litres of fuel per hour while idling.

So, with the full 52-litre gas tank, you’ll get about 58 hours of idling. If you’re down to a quarter tank, you’d get about 14.

But in an idling gas-powered vehicle, there’s the danger of carbon monoxide poisoning. That’s something that can’t happen in an EV.

“Folks tend to stay in the car as long as they can with the heat on,” said Lewis Smith, manager of national projects with the Canada Safety Council. “Asphyxiation happens more often than we like to see – make sure the tailpipe is clear of snow and turn off the car every so often.”

Editor’s note: An earlier version of the story stated a Honda CR-V would be able to idle for 47 hours on a full tank of gas and about 12 hours on a quarter tank. In fact, it is about 58 hours on a full tank and about 14 hours on a quarter tank.

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