Energy Consumption and EV Efficiency

When I was driving an Internal Combustion Engine (ICE) vehicles, I was obsessed with my efficiency. I had a device on my Civic that calculates my miles per gallon (MPG). The higher the MPG, the more efficient I was.

As we know, the MPG written on the sticker never matches up on how we actually drive. There are many factors that come into play, including speed, acceleration, weather, traffic, and more.

For instance, when I owned a Honda Civic, my MPG on the sticker was 40 on the highway, 30 in the city. However, my average was more around 26 MPG. The Civic had a 13.2-gallon tank, so on average, I would have gotten 343.2 miles (26 mpg * 13.2 gal). A stark difference from 528 miles on the highway (40 mpg * 13.2 gal) and 396 miles on the city (30 mpg * 13.2 gal). I would have hoped to be somewhere in between there.

With an EV, MPG doesn’t really make sense. They do have an eMPG rating, but for me, it’s like comparing apples and oranges at this point. We, instead, have Wh/mile. This tells our how much energy we use for every mile we drive. And this is more useful information for me because of how we measure our batteries.

The batteries on electric vehicles are measured in kWh. If you look at my Performance Model 3, it has a 75 kWh battery. With that battery, it’s rated at 310 miles. So basically if I were to drive with 100% efficiency, I should be around 241.9 Wh/mile (75,000 Wh / 310 miles).

Unlike MPG, the lower the Wh/mile, the better. Which means that if I were to sustain a rate lower than 241.9 Wh/mile, I could theoretically drive further with my current battery pack.

For instance, if I drove at a sustained rate of 187.5 Wh/mile, I could technically drive 400 miles on a single charge! (75,000 Wh / (187.5 Wh/mile)).

However over time, the battery will degrade. At some point in the future, I won’t be able to charge the entire 75 kWh battery, it might be less,. There’s currently no way for us to know how much of our battery has degraded. There’s also a discussion on whether Tesla changes the rated miles based on your driving behaviors.

So when we calculate driving efficiencies, we actually use the rated miles (miles displayed on the vehicle) and the actual miles (miles actually driven). So say that I took a trip where I drove for 75 miles, but it consumed 100 miles on my car. We would then conclude that my efficiency is at 75%.

Looking at individual trips doesn’t make too much sense, especially if it’s short. It’s too small of a sample size. I personally have 2 metrics I’m keeping an eye on. One is my Lifetime miles. The other is when I got my spoiler installed.

My lifetime energy consumption is at 300 Wh/mile. If we did the math based on my battery pack, it put me around 250 miles (75,000 Wh / (300 Wh/mile) = 250 miles)!

Since getting my spoiler, my energy consumption has dropped to 287 Wh/mile. Based on that, I’m at 261 miles (75,000 Wh / (287 Wh/mile))! A little better than before, but the sample size is still small in comparison.

As for my efficiency, you can use external apps like Stats, to determine your long term efficiency. As for me, I’m around 85% efficiency, and that number keeps going up as the weather gets warmer!

That said, I’m not focusing on a single number every time I drive. I try to aim to be under 300. I know getting below 250 might be near impossible, especially with my 20-inch rims. But most importantly, I am just here to enjoy the ride!

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