In 2020, Tesla is expected to release the Model Y, a battery-electric hatchback “SUV” that will compete with the recently announced Ford Mustang Mach-E and other crossover-type electric fastbacks.
Putting aside all the arguments why electric cars will not save the planet in general, let’s explore whether these new family wagons are even better than the environment than a comparable hybrid car.
As the benchmark for the hybrid hatchback, I will use my 2015 Toyota Prius, which gets about 45 miles per gallon in mixed driving. I will also use the comparison of the 2020 Toyota Prius Prime, which gets 54 miles per gallon in hybrid mode.
For electrics, I will use the long-range versions of the announced Model Y and Mach-E. The Model Y is reported to have a 75 kilowatt-hour battery and range of 300 miles with rear-wheel drive only. The Mach-E can be configured to have a 99 kilowatt-hour battery and range of 300 miles, again with rear-wheel drive.
There are a set of assumptions when making calculations.
First, for gasoline motor cars, is what the emissions for burning gasoline are. According to the Energy Department’s Alternative Fuels Data Center, this is about 23.5 pounds (10.66 kilograms) for the “full fuel cycle (well to wheels)”, using an estimate from a 2015 study.
Second, for electric motor cars, is the emissions from generating electricity. For Xcel Energy, that was 0.857 pounds (388.73 grams) per kilowatt-hour for its energy mix in the Upper Midwest in 2018.
Next are assumptions for the carbon emissions from producing a vehicle. Much thanks goes to the YouTube channel Engineering Explained, which has a video explaining these calculations. The studies they find create a range of possibilities for emissions. The median estimate for the vehicle without a battery is about 10 metric tonnes of carbon dioxide, while the median estimate for a 100 kilowatt-hour battery is about 11.75 tonnes.
Thus, for each of the vehicles, the rough estimates for each model’s production emissions and emissions per mile create a spectrum of options.
|2015 Toyota Prius||2020 Toyota Prius Prime||2020 Tesla Model Y||2021 Ford Mach-E|
|Emissions per mile (g)||236.88||197.40||104.12||128.28|
|Emissions vehicle (t)||10||10||10||10|
|Emissions battery (t)||0||1.034||8.8125||11.6325|
|Production emissions (t)||10||11.034||18.8125||21.6325|
Here is that formula plotted on a graph going to 100,000 miles of driving.
As you can see, the 2015 Prius has the lowest lifetime emissions until 26,190 miles, when it is passed by the 2020 Prius Prime. The Model Y passes the 2015 Prius at 66,379 miles and the 2020 Prius Prime at 83,389 miles, just under the 100,000-mile Tesla drivetrain and battery warranty. Over the course of 100,000 miles, the Mach-E keeps its title for highest lifetime emissions, only passing the 2015 Prius at 107,113 miles, after the 100,000-mile Ford battery warranty has expired.
These numbers can and will change with time. One major factor is the energy generation mix that powers electric cars. Until recently, it was possible to purchase 100-percent renewable electricity through Xcel’s Renewable*Connect program, but that program is fully subscribed and not accepting new customers. If options for renewable electricity in Minnesota do become available, it would make electric cars much more competitive with traditional hybrids. Assuming the power source is emissions-free, the Model Y overtakes the 2015 Prius after only 37,202 miles and the 2020 Prius Prime after 39,405 miles.
What are your wheels? How are you reducing your carbon footprint? Share your experiments and discoveries in the comments.feature
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