Life with an Electric Vehicle - How to Estimate your Driving Range in the Winter

Charging my 2018 Nissan Leaf in a Minnesota Snowstorm

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If you are considering buying an electric car, I’m sure you have a lot of questions. And I bet one of your questions is: Do you know all of the questions you should ask? It’s overwhelming – I remember.  And the salespeople may have answers or they may not, which doesn’t really help when you are making a large investment and a leap into new technology.   I own a 2018 Nissan Leaf and have driven it now through two winters in Minnesota.  This is my perspective on what it’s like to live with an electric vehicle.  Feel free to reach out through my contact information below if you have any questions on what it’s like to drive an electric car.

Benefits of Driving an Electric Vehicle

Before I get into this, I will refer to an electric car often as an electric vehicle. The reason I do this is because these cars are often referred to as EV for short (electric vehicle).

There are a lot of benefits to driving to an electric vehicle:

1)    Most of my charging is free – I have access to free charging at work, and I have also charged for free at Hy-Vee and Goodwill. In fact, I’ve only spent $25 on public charging in 21 months (and over 31,000 miles). This does require a call to my parents asking them for a ride from the Hy-Vee charging station after I’ve driven the 100+ mile trip down to visit them in Rochester, MN, but this round trip used to cost about $25. Now it’s free! 

This card is how you access a charging station. You will receive a card when you purchase an electric vehicle. If it’s free, you will not be charged anything. If there’s a fee, it will access a pre-paid account that you create when you set up your card.

2) Several energy providers provide discounts or rebates on the cost of installing a level 2 charging station in your home (240V outlet). Additionally, when you charge your car using this outlet, they likely offer it to you at a significantly reduced rate. Your gas bill won’t entirely go away but it will be low enough it likely drops off your radar for things you pay attention to from a cost perspective.

3)    When it’s really cold outside, you get to drive past the gas station and all of those people filling up their cars.  This is my favorite – my car charges when it’s in the parking lot or garage.  I don’t need to be standing outside next to it while it charges.

4)    Driving an electric vehicle still has some environmental impact, primarily in how the electricity was generated that is recharging your battery, but your environmental impact is lower.  I’ve read that if you charge your car with electricity from a coal power plant it is equivalent to getting 50 miles per gallon if you were driving a combustion engine vehicle.  I’m not quite sure how this was calculated as the impacts of coal and gas are different (coal causes more air pollution and releases more carbon dioxide and gas causes more water pollution and releases more carbon monoxide), but regardless, the impact of an electric vehicle is less than a combustion engine, provided that you bought the car to drive it and not as a third vehicle that you only occasionally use. If you can charge from a station powered by wind or solar energy, you’ve removed your carbon footprint that results from driving.

5)    The cost to maintain an electric vehicle is much less than a combustion engine vehicle.  I have over 31,000 miles on my Leaf and I’ve spent $26 dollars at the dealership to have the tires rotated and $6 at the gas station for windshield wiper fluid which I’ve refilled twice.  And yes, my car is up-to-date with the required maintenance per the dealership recommendations.  No combustion engine – no oil changes, no oil filters, no annoying check engine light that comes on for fuel emission standards.

6)    Another favorite in the wintertime, as there are no emissions (carbon monoxide), an electric car can turn on and heat up while it’s still in your garage.  I don’t get into a cold car, ever.

Note the temperature in the upper right hand corner - yes, an electric vehicle can drive in the extreme cold. In fact, there were several combustion engines at work that did not start this day due to fluid freezing. There is no fluid in an EV powering the car - no fluid no freezing. Combined with a setting to pre-heat itself before I walked out to the car, driving an EV in the winter is my preferred type of vehicle!

Range Anxiety

The downside to an electric vehicle is range (how far you can drive with a full battery) and range anxiety.  If you can afford a Tesla, then range isn’t a problem as the batteries on their newest vehicles edge close to 400 miles. In the summer, I drive my Nissan Leaf 125 miles in-between charges, and I don’t worry at all.  This is plenty far enough for the amount of driving I do.  The winter though causes me to pay much closer attention to my battery percentage, and the rest of this post will focus on how to safely drive an electric vehicle in the winter.

Why Wouldn’t You Just Keep Your Electric Vehicle Charged to 100%?

You can think of your car battery in the same way as your cell phone battery.  If you always have your cell phone plugged in to your charger, you will eventually have an impact on your battery life.  In the same way, you don’t want to have your electric vehicle plugged in all the time.  So when I drive to work and when I drove, I have to make a decision – do I want to charge my car? The answer is dependent on how far I need to drive before I have the next opportunity to charge.

Why Does EV Range Decrease in the Winter?

Your cell phone uses lithium ion batteries, so you already know that battery life decreases as it gets colder outside.  Additionally though, when it’s cold, you are going to be running heat in the car or the defroster, and these need electricity to both heat the air and run the fan.  As all of an electric vehicle is powered by the same source – the lithium ion battery, your range is going to be lowered when you run the heat.  Alternatively, if you have a long place to travel and need the extra range, it is an option to bring a blanket and just use the seat heaters. I’ve only had to do this once to make it down to Rochester in December (>100 miles) where there aren’t any charging stations along the highway, at least not yet. Usually I run the heat and just charge more frequently.

What is the Range of an Electric Vehicles in the Winter?

Disclaimer – I’m an engineer, and I love getting into data and statistics. If math and statistics aren’t your thing, skip the below analysis and just go to the summary section below.

How do you Determine the Range in an Electric Car?

Let’s start with a combustion engine for comparison.  You fill up your gas tank, and you note at the pump how many gallons you added.  You look at your driving distance and to calculate your fuel efficiency you divide the miles you drove by the gallons of gas you just added.  My Honda Fit used to average between 30 and 35 miles per gallon.  I think the gas tank was about 10 gallons, so I could drive between 300 and 350 miles on one tank of gas.  There was some fluctuation in there, but I didn’t really think much about it because the gas light would come on when I had 50 or so miles that I could drive before I would run out of gas, and there are gas stations everywhere.

If it’s -30F outside, my electric car can only go 60 or so miles on a full charge and the number of charging stations is limited.  I started paying a lot more attention to my car’s performance at cold temperatures.

An electric vehicle is powered by a battery that’s quoted in kW-h (kilowatt-hours).  A kilowatt-hour estimates how much power can be used within 1 hour.  For comparison, my cell phone battery holds a maximum charge of 5.45 watt-hours.  My 2018 Nissan Leaf battery is 40kW-hours. 

How far the electric vehicle can drive depends on it’s miles/kW-h rating is (same as miles/gallon of gas).  If my car gets 3 miles/kW-h, I can drive 120 miles on a full charge (3 miles/kW-h x 40 kW-h = 120 miles).

My Leaf provides driving statistics that include a miles/kW-h rating.  I can clear and re-set this data whenever I want, similar to the drive trip functionality in a combustion engine car.  In November 2019, I started trending my miles/kW-h performance.  What I noticed was that my car was significantly over-rating itself.  Meaning it was predicting I could go much further than I would actually be able to get.  To measure this difference, in December 2019, I started recording the battery percent when I got in the car, the battery percent when I arrived at my destination, and the distance that I had gone. 

Then I calculated the percentage of the battery I used (starting % - % at destination) and multiplied it by my battery’s capacity (40 kW-h).  Then I divided the total number of miles I had driven by the amount of power I had consumed.  Example: If my starting battery percentage was 100%, my ending battery percentage was 50%, and I drove 30 miles, I would have a rating of 1.5 miles / kW-h (30 miles / (40*(1-.5)kW-h).  With a 40kW-h maximum battery, I would be able to drive 60 miles [40kW-h * 1.5 miles/kW-h = 60 miles] on a full charge.

Data from my 2019-2020 Winter Driving Experiences. Blue is my car’s data, red is the data I calculated based off of the % change in battery and how many miles I drove.

The blue line is the information that was coming from my Leaf, and the red line is the data that I was calculating.  The difference is significant.  If the car estimated 3.5 miles/kW-h, and I calculated 2.8 miles/kW-h, the car is over-estimating that I can drive an additional 28 miles (3.5-2.8 miles/kW-h * 40kW-h = 28 miles).

Independent of this data, I’ve gotten used to predicting how far I can drive in colder weather and I’d already noticed that my estimated miles would drop faster than the number of actual miles that I was driving, so you don’t need to do this math to figure this out.  But since I had the data, I thought it might be useful for others to see.  I only drive 32 miles to work, and so although the above calculations from the car are off quite a bit, I’m not in any danger of my battery running out while I’m driving back and forth to work. I’m not meaning this as a negative to deciding to buy an electric car, I’m just giving you the data if you do decide to drive one so you can make informed choices about when to re-charge.

What Factors Impact Range?

While I was collecting data to determine my car’s actual miles/kW-h, I also recorded outside temperature, time in the car, and distance traveled.  Remember, I used the distance traveled in my calculation for miles/kW-h, so this is a dependent variable (I only wanted to point out that I’d considered this in my below analysis so you won’t need to comment on this).

Some other notes: If the temperature was below 32F, assume the heater or defrost was running consistently as well as the seat heater and steering wheel heater.  I hate being cold.  If the temperature was above 40F, I likely turned the heater off at some point, although the seat heater and steering wheel heater would have remained on.  I run the radio as well (technically blue-tooth to stream pods or music).  If I charged my phone while I was driving, I did not record the data for the trip. 

The most influential factor in driving range was temperature.  I’ve converted the miles/kW-h into miles the car would be able to drive assuming full charge (by multiplying the miles/kW-h with 40kW-h).  Below is a regression plot from Minitab.  The blue dots represent my actual data.  Temperature is reported in Fahrenheit.  Car Range is in miles.  You can visually see there is a lot of variation that is not explained by temperature. 

Data from driving a 2018 Nissan Leaf through the 2019-2020 winter in Minnesota

For the stats people out there, the R-sq(adj) is only 41.1%, which doesn’t represent a great model, so clearly there are other significant inputs into my car’s performance.  But in general, you can see as the temperature goes down, my car’s range decreases.  I’ve also displayed confidence intervals (green line) and prediction intervals (purple line) for those interested, but the model is so poor it predicts my car could travel somewhere between 30 miles and 90 miles at -10F.  That’s a bit extreme in terms of model variation.  I don’t worry about driving 32 miles to work on a full charge at -10F.  In fact, as long as I have 65% battery charge, I’m comfortable driving to work at -30F (from 2018 – it didn’t get that cold in 2019/2020 – at least not yet…).  Also, I wouldn’t assume that I could get 125 miles at 40F.  I would estimate that around 40F, I can usually get close to 100 miles.

I also looked at the impact of time the car was running.  As the line is flat, there isn’t an impact.  For those curious, the times around 15 minutes are my frequent trips back and forth to church, piano, and swimming lessons.  The rest of the times are my commutes back and forth to work.  The longer times involved snowfall.

Range estimate based on time the car was running.

Lastly, I used a Regression Analysis in Minitab to include the potential of interactions with inputs.  My R-sq(adj) rose to 60% so I was able to capture a little more of the significant factors, but there is obviously some input(s) that I have not been able to observe (use of cruise control, wind speed, or something else I’m unaware of).

Summary of Key Factors Affecting EV Range

If you skipped the math and graphs, the bottom line is that outside temperature will have a significant impact on your electric vehicle’s range.  If you are driving at temperatures 32-40F, assume you will be able to go about 1 mile for each % of your battery.  If you are driving at temperatures 0-32F, assume you will get about .75 miles for each % of your battery.  Below 0F, assume you could get as low as .5 miles for each % of your battery.  When temperatures are below -10F, just charge your car at each available opportunity.  If you slide off the road at those temperatures, the ability to have heat is more important than the impact of the hopefully limited days in a winter you will have at these temperatures.  Or better still, stay home on those days if that is an option 😊.

An additional conclusion is that there is large variability that is not captured fully by outside temperature.  Until those factors are understood, I tend to charge more conservatively (meaning keeping my battery more charged) than I do in the summer just to be on the safe side.

How do you adjust to a shorter range?

The short answer to this is simply planning.  If it’s in the winter, and I have over 45% battery, I will drive home and charge there.  If I have less than 33%, I will charge at work.  If I’m somewhere in-between then I’m paying attention to the temperature.  If it’s over 32F and I’m going straight home I won’t charge.  If it’s less than 32F or I have somewhere else to drive that evening I will charge.  Ultimately this car takes out spontaneity.  But to be honest, that time of my life (where I decided I want to go shopping at the mall on my way home without having this pre-planned ahead of time with my husband) ended when we had kids.  The hardest thing in the winter is when my husband asks me to go somewhere in the evening that I didn’t know I would need to go, and I might not have enough charge.  He doesn’t typically drive the electric car, and hasn’t adjusted yet to the pre-planning that’s needed.  Seeing the above graphs regarding range variability in the winter though has helped give him perspective in our discussions about planning out the week ahead of time.

What if You Forget to Charge your Car?

Yep, it happens.  You are talking with your kids when you get out of the car, and one child is telling you what homework needs to get done that evening while your other child is telling you a story that happened in the cafeteria and you are unloading the car with bags from the grocery store while thinking about what you need to make for supper and that you need to remind your husband that the you have a late meeting at work on Wednesday and that he will need to take the kids to church, and you forget to plug your car in.  Eventually you will be in the habit so much that even if you forget initially, you’ll remember in the next few minutes and run back out to the garage to plug it in, but I have completely forgotten to charge my car twice in 21 months.  And those mornings suck.  You will need a new plan for the day that involves calling into your first meetings while you sit in your car and charge at a quick charging station on your way to work.  It’s life, it’s not always perfect.  Always know your charging options, especially in the winter.  The two apps I use to find charging stations are ChargePoint and Greenlots.

What if You Run Out of Battery?

This hasn’t happened to me, nor have I come close.  But keep in mind that if you do use all of your battery charge, this means something different than when the battery on your combustion engine vehicle dies.  In that case, you can ask someone to give you a jump.  You can’t jump a dead battery on an electric vehicle.  You will need to get it towed to a charging station. 

Should You Buy an Electric Vehicle?

I drive 64 miles a day in Minnesota, one of the coldest parts of the United States. I live out in an exurb where charging stations are limited, and I don’t yet have a level 2 charging station at home.  So I think I’m one of the more extreme case studies that shows you can thrive with and whole-heartedly love an electric car.  It does require planning ahead so having consistent schedule or at least a schedule that you know of ahead of time helps.  There are also days that something doesn’t quite go right (if you forget to charge for example) and you have to be able to laugh about it and move on.  I would suggest test driving one at least the next time you need to purchase a car, and if you have questions about living with an electric vehicle that your salesperson can’t answer, please feel free to reach out and I can give my personal experience.

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