# Efficiency versus Efficiency

My wife was reviewing our logs to do our taxes. Being the awesome numbers person she is, turns out she records the beginning and end mileage of my truck each year; I had no clue. From this, I found out that in 2013 I drove a grand total of… [wait for it]

2,884 miles. To answer your next question: no, I don’t know why I have a vehicle.

On the bike for 2013, I rode 5,167 miles not counting the trainer, because well, who does?

Bikes are by their very nature extremely efficient machines. Even the cheapest blue-light special bike from your local big-box store is about 80-85% efficient at converting the power output from your body into forward motion. A decent road bike? 90-95%. A mid-to-high end road bike? 97%+. A high-end Olympic-level velodrome time-trial bike? Over 99% efficient. Insane, right?

All this got me thinking: how efficient are all those miles I rode on my bike versus those I did in my truck? The more I thought about it, the harder this was to answer. See, efficiency isn’t a simple subject. When talking about efficiency, you can limit your scope to just energy efficiency – converting potential energy (in glycogen or gas) into kinetic energy. But doing that, we’re leaving out quite a bit of the overall picture. There’s temporal (time) efficiency, economic (money) efficiency, and loads of other types. Let’s break them down, get them all into similar units, and see where my bike and my truck really land.

ENERGY

This is an easy one. My truck gets about 17 miles/gallon of gas.

On my bike, I burned some 177,500 Calories while riding. There are 31,500 Calories in 1 gallon of gas. So riding this distance (assuming I could metabolize gas and, you know, not die) would require 5.63 gallons of gas. That’s 917 miles/gallon.

This means riding my bike is almost 54x more energy efficient than driving my car.

TIME

That energy efficiency doesn’t come without cost. For those  5,167 miles on my bike, it took me 287.8 hours to cover that distance. That’s approx. 17.95 mph. Not bad for pedal-power. But that’s just moving time. For a typical 2.5 hour ride, I stop for about 12 minutes on average (rest stops, lights, etc.). So there’s about another 23 hours of non-moving time associated to my ride time. Now we’re at about 310.8 hours.

But wait, there’s more. When I have to drive somewhere, I grab my keys and drive. For the bike? Not so. Gotta change into a jersey and shorts. Gotta put my riding socks and shoes on. Check my tire pressure, grab water/food, helmet and gloves. Throw on sunblock for the sunnier days, more clothes for rainy/cold days. Even after a lot of practice, it still takes about 15 minutes to prep for a ride before I actually roll out. I did 115 rides in 2013. That’s another 28.75 hours minimum, for a total of 339.55 hours (let’s call it 340). Now my average speed has gone from 17.95 mph down to 15.2 mph. Almost 15% of my total time for riding 5,167 miles is used not riding at all.

Total time for driving that’s not used for driving: 0%.

And we’re not done yet. We now know it took almost 340 hours to ride my bike almost half the distance of the continental US border. But how long would it take to drive? I’m going to make a few assumptions here. My average drive is about 11 miles (I checked most of my weekly destinations, and they’re all within that distance). It takes about 12-15 min. depending on traffic (let’s call it 13.5). For 2,884 miles, that’s about 49 mph (most streets here have speed limits of 40-50 mph, plus about 2/3rds of my driving is on turnpikes/highways). For 2,884 miles, that’s 59 hours. At this rate, it would take 105 hours to drive 5,167 miles. Just to keep things fair, let’s remember that I have to get gas while 16 times in order to drive that distance. If it takes an average of 12 min. per refuel, that’s another 3.2 hours, for a grand total of 108 hours.

That’s 232 hours less time!

A bike might be more energy efficient, but requires some 3.15x more time to cover the same distance. And the farther we drive, the higher our average driving speed (more time on roads with higher speed limits), pushing this to as far as 4x longer to bike than drive. When time is money, this can get pretty expensive.

MONEY

And speaking of money… how often have you heard, “Hey, my bike isn’t a gas guzzler. I’m saving money!” Slow down. You only think you’re saving money. But have you done the math? Let me take a crack at it.

First, I own both my bike and truck out-right – no payments. So they’re on equal footing (or rubber, as it were).

My truck gets about 17 miles/gallon (better over longer distances, but not by much). For 5,167 miles, that would use 304 gallons of gas. At \$3.25/gallon, that’s \$988 for the year. But that’s just for fuel. For a year, I have to get four oil changes (call that \$30/per), for another \$120. My truck didn’t require any other maintenance, so the total (assuming I drove as far as I rode) would be about \$1,108.

What did it cost me to ride my bike all of those miles in 2013?

\$140 for two sets of tires
\$70 for two chains
\$65 for a cassette
\$85 for shop maintenance
\$38 for two sets of handle bar tape
\$42 for six inner tubes
\$10 worth of CO2 cartridges

Total: \$450. We done? Nope. I bought clothing (yes, shorts wear out people!!! PLEASE don’t wear see-through shorts!). I got good deals on my clothes, but it still wasn’t cheap. About \$200 worth of clothing (shorts, gloves, etc.). You don’t need special clothing to drive a truck.

So far, we’ve covered the maintenance and gear. We haven’t covered fuel. What’s that I hear? “A bike doesn’t use fuel!” Heh, you’re right. But you do! At the Caloric equivalent of 5.63 gallons of gas to cover 5,167 miles on a bike, with a cost of \$3.25/gallon, that’s only \$18.30. Unfortunately, we can’t metabolize gas. So, how much food is needed to create the Calories I burned for riding in 2013, and how much does it cost? Let’s break it down:

287.8 hour x 95.8 Cal/hour (my maintenance Caloric burn rate) = 27,581 maintenance Calories
– calories I would’ve burned even if I wasn’t riding

177,500 Calories (total during riding time) – 27,581 Calories (maintenance) = 149,919 (used for riding only)

Maintenance Calories / day = 2,300 (yes, I run hot)

149,919 Calories (for riding only) / 2,300 Calories/Day (maintenance) = 65.2 Days worth of Calories

It took me an additional 65.2 days worth of food to power my riding! That’s an additional 17% of my Calories for the year, or about 1 extra meal for every six normal meals. Contrary to popular belief – and ironically given the starving populations and the poor – food in the U.S. is rather inexpensive (especially when you don’t eat healthy, and I don’t eat particularly healthy foods). According to the USDA average family spending, we spend about \$7/day/person. I’ll push that to \$8, to use a higher-income margin (you tend to eat out more and spend more the more you make). Using this number, this additional food cost is \$522 for those 5,167 miles.

Let’s add it all up: \$450 (maintenance) + \$200 (clothing) + \$522 (food) = \$1,172. Uh oh, wait a minute, what’s going on? This total is higher than what it cost me to drive the same distance in a year. Even if I exclude my clothing costs (assuming my clothes last that long), then it’s still \$972, or a savings of \$163, or \$0.0263 per mile!

So the cost of fueling and maintaining both vehicles appears to be very close. More fuel-efficient autos might beat out the cost of cycling when talking longer distances. Cheaper bike components or cheaper food purchasing could make cycling cheaper.

NOTE: When you start to count in driving-specific costs that don’t apply to cycling (like insurance and toll roads), then cycling becomes the clear winner (insurance alone can double the cost of driving relative to cycling).

TIME + MONEY

We know that it takes 232 hours less time to cover the same distance in my truck as it does on my bike. If I made \$20/hour (and assuming I had no life and just worked any free time), that’s \$4,700 that I could’ve earned working instead of riding to/from destinations. If we only count fuel costs for both vehicles, my truck costs double the amount my bike costs to fuel, but even with the additional fuel cost the time savings (converted into hourly wage work) would still net us some \$4,100 more than riding. Even if we just watched TV for half that time and worked the other half, that’s still an extra \$2k per year made by driving instead of riding.

Adding in the additional costs of vehicle ownership (insurance, registration, toll roads, etc.), this savings is eliminated, unless your hourly rate increases as well. So, though minimum wage people would save money if they rode bikes, as your income increases so does your earnings when you drive and convert those saved hours to payable work.

HEALTH

Remember that extra money we made while driving? Here’s where it’s spent. Cycling does burn a lot of calories (which costs a lot in food fuel). But it also builds muscle, strengthens the cardiovascular system, and has a myriad array of other beneficial health effects.

Driving… has none. Not only none, driving actually has negative health effects. It produces smog. It’s sedentary: by pulling numbers from fatsecret.com, excluding maintenance Calories, I would’ve burned 2,751 Calories driving the same distance I biked. In other words: almost nothing – 0.53 Calories/mile. On the bike, I burned an additional 29 Calories/mile.

Another big one: stress. Cycling is a stress reliever (as are many other forms of exercise). Driving is typically a large stress inducer. And stress is cumulative. The more you drive, the more stressed you get.

CONCLUSION

Cycling is efficient in converting energy to forward motion. It dissipates stress, encourages health, and has a far lower lifetime cost of ownership (I didn’t go through those calculations). With my minimal truck usage, my usage cost is rather low, and my biking cost is rather high. However, due to the nature of our suburbanized lifestyles, when time is of the essence, there’s no contest: driving wins hands down, and can save you a lot of money if that additional time can be spent making money. Whether it’s worth all the additional stress… that’s a whole other article.

I hope you enjoyed this walk down theoretical lane. Now back to our regularly scheduled riding.

Semper equitare.