So my nifty SportyPal app on my new phone, which keeps track of my bike ride home, tells me that I pretty reliably burn about 420 calories during the trip. Because I’m a geek, that got me wondering how much less energy is used while biking versus while driving. I crunched a few numbers, and this is what I came up with.
420 kilocalories (1 kilocalorie = 1 food Calorie, yes, it is confusingly stupid) is about 1.8 million joules of energy. My car gets around 22-23 MPG in mixed driving, so let’s pretend that my trip home uses 0.4 gallons of gasoline. One gallon of gas has around 125 million joules of energy, so my drive home uses 50 million joules. That’s over 25 times as much energy expended as biking, which is needed to move all that extra weight around.
Another fun fact: if it took 50 million joules of energy to bike home, that would require using about 4 pounds of body fat as energy. If our bodies used as much energy traveling as cars, people would have a far easier time losing weight! Considering how much waste heat would be generated in the process, though, we’d have to have huge radiators attached to our bodies somewhere.