Saturday, March 23, 2024

Electric gas-mileage equivalents

A few days ago I came across a video from a group called Out of Spec Studios who do reviews of various electric vehicles, where did a range test on four electric pickup trucks, the Tesla Cybertruck Cyberbeast, Rivian R1T Dual-Motor Large Pack, Chevy Silverado EV 4WT,  and Ford F-150 Lightning Extended Range. It's a fairly entertaining watch with the editing and personalities involved; they charged each truck up to 100%, then drove them around (simultaneously) on the freeways at 70 miles per hour around Colorado/Wyoming/Nebraska until they ran out of charge to test their range in real-world conditions. (Along with a trailer-mounted diesel generator-powered fast charger for rescuing each one when they ran out of charge!) But what caught my attention was the efficiencies they calculated at the end of the test (and shared up-front in the video, which is pretty awesome).

The efficiencies came out in miles per kilowatt hour (mi/kWh), which I found interesting as I didn't know how to compare it to what I'm more familiar with, miles per gallon (mpg). It turns out there's a value for this, called miles per gallon gasoline equivalent, or MPGe. It's also a very simple conversion: one (U.S.) gallon of gasoline is considered to have 33.7 kWh of energy (though this is only for a theoretical 100% efficient conversion of the chemical potential energy to heat and work; in reality it's always lower). 

The four vehicles tested got 2.0 to 2.6 mi/kWh, which (multiplying by 33.7 hWh/gallon) translates to 67.4 to 87.6 MPGe. My 2018 Nissan Rogue has what I'd consider pretty good gas mileage (despite the hilly terrain of Hilo doing it no favors), and it's only rated at 25 mpg in city driving, or 32 mpg on the highway. (Though it informs me that the last few drives have been closer to 20 mpg, in practice.) That's quite a difference in energy efficiency!

For a different perspective, I looked at comparative costs. By inverting the mileage values and multiplying by the costs of electricity and gasoline, the four electric trucks would theoretically have costs in dollars per mile of $0.19/mile to $0.25/mile (based on the average price of $0.50/kWh for residential electricity). My Rogue, arbitrarily using the cost of gas of $4.88/gallon I saw a few days ago where I usually fill up, would vary from $0.15/mile to $0.18/mile for its highway and city ratings, respectively, so pretty comparable, overall.

I don't have a point to make from all this, I just got curious enough I thought it'd be fun to do some math. Personally, I'd love to have an EV; the allure of being able to charge at home and basically never having to stop at a gas station again is very strong. I didn't get one in 2021 after moving back to Hawaii for a few reasons, primarily the inventory shortage and lack of options at the time, but also the uncertainty in where I would end up living; and since I live in an apartment complex with no place to charge, my Rogue turned out to be for the best for now. It's in good condition and I hope to be able to get plenty more years of use out of it, but hopefully it can also be the last internal-combustion engine vehicle I own. Who knows what the future holds! A hui hou!

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