Is Environmentalism Passé? Part 3
Should I care about MPGe?
I usually try to not get too technical with this Substack. But I’m afraid that in this post we’re going to dive into a bit of jargon. We’re going to explore a recent EPA invention: “MPGe.”
Before we get to it, let me first start with an acronym you probably already know: “MPG.” That, of course, stands for “miles per gallon” and basically tells you how far you can drive in a gasoline powered car with a single gallon of gas.
Anyone with an odometer and gas receipts should be able to calculate MPG.* But in the United States, the Environmental Protection Agency (EPA) issues official MPG ratings for new cars. Since 1971 the EPA has tested each new car to determine the MPG it gets on the highway and the MPG it gets in city driving, and then calculates an official combined number that is based on 55% city driving and 45% highway driving. The EPA does this to give buyers the tools they need to select cars that are more fuel efficient and to give manufacturers that build extra efficient cars bragging rights.**
Whether EPA’s MPG rating system is the direct cause or not, vehicles sold in the US have gradually become more efficient. In 1975 the average fuel economy of a new car sold in the US was well below 15 mpg. It’s steadily climbed over the last 50 years and the current new car fleet is just about twice as efficient as what we were driving in 1975. [Note that there was a bit of a dip in the 90s. That was largely the result of a shift in values. During that time period Americans were looking for safer vehicles, quieter vehicles, and big SUVs and pickup trucks. Maximizing those values significantly increased the weight of our vehicles, and led to a decline in efficiency.]
With the advent of electric vehicles, the EPA decided it needed a figure that it could use to compare the energy efficiencies of EVs with gasoline powered cars. To do this, in 2010 the EPA invented “MPGe” and defined it as the distance an electric vehicle would go “using a quantity of fuel with the same energy content as a gallon of gasoline.”
Now, while I’ve seen this designation on EVs frequently. I’ve never taken much time to think about it. My car gets 117 MPGe and this seems so insanely high compared to what I get in my gasoline powered car (27 mpg), that I just smile and figure I’m doing something right.
But I think it’s worth taking a deeper dive into MPGe.
For instance, we should note that there’s a very good reason why my EV gets “117” and my gasoline powered SUV gets “27.” First, electric motors are significantly more efficient than the gasoline engine in my SUV. EV motors typically can convert something like 85% of the electrical energy in them into mechanical energy that moves your car forward. Gasoline engines, on the other hand, run on small explosions and each of those explosions generates heat and light that doesn’t all get converted into energy that keeps you going. Even my relatively efficient 4-cylinder SUV engine produces 7,000 explosions per minute when I’m cruising on the highway at 3,500 RPM. If I’m lucky, 30% of the energy in that gas is ultimately used to move the vehicle.
Second, my EV is designed to be as aerodynamically efficient as possible. The manufacturer put the door handles flush with the side of the car, closed up the grill, and gave it a weird back end, all to allow it to slip cleanly through the air. The result is a car that has a “coefficient of drag (Cd)” of “0.21,” one of the lowest available on a car today. My SUV probably has a Cd of something like “0.4”. I won’t go too deep here, but your aerodynamic efficiency is based on your “Coefficient of Drag” times “Frontal Surface Area.” Given that my SUV has a Cd that’s twice my EV’s and it has a much larger surface area, it’s losing a lot of energy trying to cut through the air.
So there are good reasons why EVs are more efficient than gasoline powered cars. But that doesn’t mean that all EVs are equally efficient. In fact, the MPGe numbers of cars can vary quite significantly… and this is a big part of the reason why the EPA invented the statistic.
My neighbor will be excited. According to the EPA his new Lucid Air is the most efficient EV out there right now. Depending on the exact configuration it can get 146 MPGe. At the other end of the spectrum is a car that has a legacy of consuming energy: the Hummer EV SUV, which gets 47 MPGe.
Both those numbers are reasonably astounding. The Lucid (made around the corner from me in Casa Grande, AZ!) gets ten times the efficiency that the average car did in 1975. That’s quite an improvement. The Hummer EV, on the other hand, is 20% less efficient than a gasoline powered Prius.
That last ding on the Hummer, however, might not be exactly fair. It is kind of like comparing apples and oranges… where the apple weighs 3 times as much as and can accelerate from 0-60 twice as fast as the orange. It’s clear that electric power allows that apple/Hummer to do pretty incredible things.
But the question is… what do we want electric vehicles to do? As I’ve mentioned in the last few posts, the primary goal in the big push for EVs over the last forty years or so has been to reduce the impact of driving on the environment. Today, however, some of our EV technology is focused on creating a nearly 10,000 pound vehicle that can accelerate to 60mph in 3.5 seconds. I don’t remember them talking about that on Earth Day in high school.
I guess in the end I’m not morally offended that the Hummer EV exists. After all I’ve had posters of supercars on my wall that were not exactly fuel efficient. But I do fear that we’re losing sight of those environmental goals that once seemed inseparable from electric cars.
Alas, this hits all too close to home because the second most fuel-efficient car on the EPA’s 2024 list is the car I almost bought. As I mentioned in the last post I chose the EV model I wanted, but was then torn between the version with the nicer interior and the one that got better mileage. The soft, supple vegan leather seduced me and I drove away in the car that gets 117 MPGe instead of 140 MPGe.
Since I bought my car I’ve been working to try to find out what makes the other version so much more efficient. I thought maybe my version was extra heavy because it has a really nice radio or something. But after much searching I think there is only one fundamental difference…
They have different wheels.
My car came equipped with 20-inch wheels. The more efficient version has 18-inch wheels.
What difference does the size of a wheel make? Quite a bit actually. 18-inch wheels are easier for a motor to spin, so they’re more efficient. And they typically have a thicker sidewall so they cushion bumps better. There are two basic benefits to 20-inch wheels: 1. They have a thinner sidewall, so they may help make handling a little more precise; and 2. they “look cool.”
I am reasonably certain that it is this final factor that played into the upscale versions of my car having 20” wheels. I find this particularly frustrating because I’m not a fan of the recent trend in oversized wheels. I kinda think they look silly. I’d much prefer to purchase a car with a nice interior and efficient wheels. Alas, they don’t make that car available to the public.
This brings me to my final point. I think there is room for EVs that prioritize many values other than lowering environmental impact. But I hope the hype around all the amazing things that EVs can do doesn’t drown out the voices of those of us who are drawn to electric cars for environmental reasons. I’d like manufacturers to work to make EVs twice as efficient as they are today in something less than 50 years.
Is Environmentalism Passé? Part 1
Is Environmentalism Passé? Part 2
* I used to keep track of mileage and how much gas I put into my car and every couple months would sit down with a calculator and do the math. This practice was handed down from my father who did it religiously on all our vehicles. The idea wasn’t so much to determine how far I could go on a given tank of gas. (Range anxiety was not something I suffered from before I got an EV.) Rather, the thought was that if there was a significant decrease in MPG from one month to another, there was a decent chance that something was wrong with the car and you should have it looked at.
**It doesn’t always work. The Hummer H2 was considered a glamorous car in the early 2000s and it was rated at just about 10 mpg. Without its massive 32-gallon fuel tank, a few Hummer drivers would have experienced range anxiety back in the day.