EVs have big batteries. I’m talkin’ big ol’ batteries, baby. None more so than the GMC Hummer EV. This hefty electrotruck has a battery pack that weighs 2,923 pounds. It boasts a total capacity of 246 kWh—more than two Tesla Model S’s put together. And yet it pales in comparison to what a 1989 Geo Metro is packing in its diminutive little gas tank.
Today’s EVs struggle with one thing—energy density. Even our best batteries can’t hope to compare to the energy packed into delicious hydrocarbons like diesel and gasoline. That means a Geo Metro is hauling around more chemical energy in its gas tank than a Hummer EV with a fully charged battery.
Put your metric pants on, because we’re looking at some basic science, and unlike Hank Hill, I refuse to use BTUs. We’re gonna see just how GMC’s massive off-roader measures up to ancient hatchback in a way that ultimately doesn’t matter in the slightest. Let’s go.
Let’s Talk Turkey
Real talk, gasoline is positively brimming with energy; that’s probably not surprising given that some cars can get you a ridiculous 50 miles with just a milk jug’s worth of the stuff. Gas contains around 46.4 megajoules of energy per kilogram; measured by volume instead of mass, gasoline comes in at 34.2 MJ/liter or around 130 MJ per gallon.
[Ed Note: If we convert that to kWh per gallon, we can end up with a range, though the EPA typically says a gallon has 33.7 kWh of energy (121.3 MJ).
To put that into context, one gallon of gasoline, which weighs about six pounds, has the same energy as a 2017/2018 BMW i3’s entire battery pack, which weighs about 560 pounds. (To fairly compare, you’d want to add the weight of the gas car’s tank/pump, too, but that’s maybe 50 pounds). -DT]
Clearly, batteries are not nearly as grand as gasoline when it comes to energy density. Ultium lithium-ion batteries measure in at around 1 MJ/kg. Volumetric energy density is not much better, at around 2.27 MJ/liter. Gasoline is thus around 40 times better than GM’s current battery technology in energy per unit weight, and 15 times better in volumetric density. That’s on a per-cell basis, by the way—not counting all the extra volume and weight taken up by the battery pack structure itself.
So let’s go ahead and calculate the energy in a Geo Metro fuel tank. The fuel tank of the Metro has a capacity of 10.6 gallons, or 40.1 liters. Multiply that by the energy density of gasoline, and we find out the Geo Metro is hauling around 1371.42 MJ of energy in its fuel tank (380 kWh!). Maybe a squirt more if there’s some fuel in the lines.
The Hummer EV comes up short by comparison. At its full capacity, the battery stores 888.48 MJ or 246.8 kWh of energy. That’s only 64% of the energy in the fuel tank of the Geo Metro! Oh, and you can’t use all of that. Only 212 kWh is “usable,” or roughly 763.2 MJ. In contrast, the Geo Metro will pretty much let you drain the tank.
As an aside, consider this. The battery pack in the GMC Hummer EV weighs 66% more than a whole Geo Metro, and by itself, it won’t get you anywhere.
You might think with all that energy on board, the Geo Metro would get much farther down the road. Let’s pencil it out—you metric haters can join back in here. It’s got 10.6 gallons of fuel on board, and it’s rated at 45 mpg highway. Multiply that out and you get a range of 477 miles.
GMC rates the latest Hummer EV for just 381 miles of range in comparison. The official EPA rating has the 2024 model still pegged at 314 miles at best.
Those figures aren’t so bad for the Hummer, though! It has just 55% of the usable energy on board. At 9,640 pounds, it also weighs over five times as much as the Geo Metro, and perhaps more importantly, its aerodynamic drag is way, way worse. And yet, it achieves somewhere between 65% and 80% of the range of the ancient hatch! It also has 1,000 horsepower — the Metro, just 55 ponies. You can thank the hugely substantial increase in efficiency of an EV powertrain over an ICE powertrain for that. You can see that it can go 54 miles on 33.7 kWh of energy (MPGe) whereas the Geo can only get 41 miles on 33.7 kWh (the energy in one gallon of gas).
What does all of this mean? Nothing, really. It’s just a fun comparison between the sheer amount of energy you get in a gallon of gasoline, versus the weedy amount stored in a lithium-ion battery. Feel free to take this tidbit as a line for your next dinner party. “Did you know the Hummer EV has less energy in its three-thousand pound battery than a Geo Metro has in its tiny 10-gallon gas tank?” you’ll say. And everyone will think “You interesting, handsome, and urbane bastard. Bless you.” Or something.
[Ed Note: I’d like to just that I had a chat with Peter Rawlinson, the CEO of EV company Lucid. I asked him: What do we do about big vehicles like pickup trucks and SUVs, especially ones that want to tow? How do we keep those cheap? His answer, believe it or not: internal combustion. Yes, the leader of an EV company says the answer is internal combustion, and why? Because he’s an engineer who runs the numbers. Gasoline’s energy efficiency is simply incredible, as Lewin just showed, and that’s key when your vehicle is so big it requires loads of energy just to get down the street, and especially to tow.
Also, I’d like to highlight a quote about the GM EV1. From my article on my never-before-seen engineering documents:
“I said, ‘Roger, just keep in mind what we have here. We’ve got about a gallon of gasoline worth of energy in those 870 pounds of batteries, and we effectively re- fuel it with a syringe‘” is an amazing quote from former president of energy and engine management, Don Runkle, referencing former GM CEO Roger Smith (via Automotive News)
Note that the EV1 only had up to 26.4 kWh of battery, so really it was less than a gallon. Anyway, many of you engineers probably knew all of this stuff, but hey, we like writing about the Geo Metro! -DT].
Image credits: GMC, Geo, EPA
The post Here’s How Much More Energy A Geo Metro’s Tiny Gas Tank Has Than The Hummer EV’s 2900 Pound Battery appeared first on The Autopian.
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