More on pouring away gas

January 26, 2007 7:53 pm

This is something I’ve had stuck in my mind ever since I read the book “Stuff: The secret lives of everyday things” (or was it “Natural Capitalism”? I’ve lent out both books right now).

Take a wild guess at how much of the energy in the gas you put in your car actually goes towards transporting you. Don’t be afraid to lowball it. Write it down.

How did you go about it? Did you use the fact (which is fairly common knowledge) that car engines are about 30% efficient? Good. But 30% is not the answer. Did you pay attention to how the question is worded? “Towards transporting YOU”?

How about idling, energy lost in the driveline, energy lost on powering accessories in the car? With all that, about one-eighth (12.5 %) of the energy reaches the wheels. Around half of that heats the tires, road and air that the car pushes aside. That leaves about 6% or so applied to moving the car forward. When you figure in that your mass compared to the car’s mass is about 5%, that leaves less than one percent of the energy in the fuel for transporting YOU. Let’s be generous and say it’s actually one percent. Here’s a little visual of that number for you:


That’s a scary waste in my book.

Here’s more to make you think: A friend of mine, Stan King, did some calculations based on a discussion we had at a recent simplicity circle meeting at our house. I had wondered how bicycling compares to driving in terms of energy efficiency. He took on the task of figuring it out. When you convert the amount of energy needed to bike a mile and convert that to the car’s miles-per-gallon equivalent, riding a bicycle has a “miles-per-gallon” of about 650. That number makes hybrid cars pale in comparison.

When you consider that 99% of the energy in the gas is wasted on things other than transporting you, the passenger, riding a bicycle has a “miles-per-gallon” of over 6500.

Compared to that, hybrid cars seem almost like stone age technology.

This is the thinking behind our family’s decision to stick with one car, even though it creates some inconvenience. It’s also why I bike to work practically every day.

And just so you won’t think I pulled these numbers out of thin air, there’s a Wikipedia article that states a 653 mpg for bicycling, which matches Stan’s number well. The calculation on the efficiency of cars can be found in this article by Amory Lovins from July 2006. The journal this was published in can be downloaded here (3.17 MB PDF).

13 Responses to “More on pouring away gas”

Pearl Jam wrote a comment on April 20, 2007

How about the amount of energy wasted by running Windows Vista on computers? With the higher CPU requirements, higher power consumption, I think we are better off using Linux / Mac OS X, anything basically that is not Windows Vista

GeekTieGuy wrote a comment on April 20, 2007

Thanks for the comment! At the risk of emarrassing myself (and my future self): I’m excited to have someone actually comment on one of these non-tech posts.

Your thoughts sound interesting. Have you actually compared running Linux or OS X versus running Vista? Some data would make a nice case.

I’m not sure that Vista is really all that much more demanding on your processor than previous Windows versions. I have several computers that are over three years old that run Vista just fine. However, one thing I know for a fact is that Vista will use a 3D graphics card much more than its predecessors, simply because the core screen rendering engine is written to take advantage of the GPU on the card if one is found. This is very obvious on laptops that have a Vista Aero compatible graphics card. They tend to have shorter battery life. I’d like to see some numbers on that, though. Do you have any information to refer me to?

A trend that’s going on in the PC industry is more focus on “performance per watt”, in other words making processors more capable while lowering the power consumption. This should benefit all computer users over time.

I personally like Vista quite a bit (indirectly, it puts food on my table, since I write software for it), but I’m using Linux on a server that runs as my gateway/firewall, so I’m certainly not against the idea of using alternative operating systems. At some point I want to give Ubuntu a try. Maybe this would be a good kickoff for doing that.

If you want to get really into the heart of it, we should all just stop using computers completely. They are among the most problematic hazardous substances to get rid of, and they become obsolete so fast it’s really quite a shame. But we all know that’s probably not going to happen.

Pearl Jam wrote a comment on April 20, 2007

Well, that was just a flamebait. I just wanted to make some conversation. I too bike to work and work with Microsoft .NET everyday. Just that Windows Vista has not worked for me. I have tried it on three different machines, and everytime has been a miserable failure. My Dell laptop ran like a dog after Vista. On my Sony Vaio UMPC (UX-280p), the CPU fan was always on after I installed Vista. And don’t get me started with the painful 4 hour installation process. Anyway … glad it works for you 🙂

Leila wrote a comment on April 21, 2007

Hear, hear!
Now to convince drivers that we bicyclists actually belong on the road, not the sidewalk.
*runs off to ride bike downtown*

Keesa wrote a comment on May 10, 2007

Maybe you have some advice for me…where I live, it’s about 6 miles to the grocery store, one way. That’s NOT a huge distance for me to bike. But the only road is a heavily-traveled highway (speed limit 55, not that anyone follows it) with no bike paths. Not safe.

How can I go about making that road bike-able? Surely it’s not a lost cause?

GeekTieGuy wrote a comment on May 12, 2007


I’m not sure how you would do that exactly, but maybe going to city hall and raising the issue would be a first step?

Peter wrote a comment on May 13, 2007

Thanks for the article. That is very interesting data. Of course, you must realize, that while a bulk of the population of the United States lives in urban areas, many times people can be in the suburbs and the jobs in the downtown area. Not every city has a subway/viable public transportation for bicyclists. Also, let’s not forget that there are many people who live in rural areas, and the road conditions can be all but favorable for bicyclists. I have not been very big into cycling, but recently I’ve had “duh” moments when I realized that bikes can provide so much (fun, efficiency, exercise, et cetera). Thanks again for the post.

Eli wrote a comment on June 25, 2007

Keesa; Biking on this road is probably quite doable. You just need to learn the rules and get comfortable following them. It is scary and counterintuitive at first but it really works. I recommend reading “Effective Cycling” by John Forester. It was a major revelation for me.

JohnM wrote a comment on September 18, 2007

Regarding biking to work, check out How to Ride Your Bike to Work.

Mark Foecking wrote a comment on April 12, 2008

It is true that on a calorie equivalent basis, that a bicycle gets about 600 mpg. However, since the average American diet takes 10 calories of fossil energy to make 1 calorie of food, cycling get more like 60 mpg. Of course, one would still eat whatever your form of transport, so the advantage is still o the bicycle. I’m just pointing out that bicycle eficiency hinges heavily on the energy inputs of one’s food.


Practicing What You Preach | Ride Earth sent a pingback on November 5, 2009

[…] Interesting article on how much fuel in a car actually goes on transporting you and why bikes are gr… […]

Draught Excluder wrote a comment on April 28, 2010

Great post – love the diagram.

I heard this from Amory Lovins, who explained that if you halve the weight of a car, you can cut the fuel consumption by a massive amount (like 75% or something).

Also, the faster you drive the less economic your car is as air resistance becomes very large above 30-40mph.

Practicing What You Preach | Slow Quest sent a pingback on December 19, 2011

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