Thursday, November 27, 2008

The Cost of Bike Commuting

When I tell people that I ride my bike to work, invariably their first response is, "Oh, think of all the money you're saving!"  Although money isn't the primary reason I bike to work, I always smile and nod and say something like, 'Yes, I suppose I do.'  But I've always wondered whether I'm really saving as much as everyone seems to think.

Actually, it's easy to show that I'm not saving anything.  I have been recruited into a van pool, which I sometimes take.  The cost is covered 100% by my company.  So I could reduce my commuting cost to zero if I felt like walking the 1.3 miles to the van pool pickup every day.  Even bike commuting can't compete with zero.

Unfair comparisons aside, what does bike commuting really cost compared to driving?  I woke up feeling bad one morning and called in to work sick.  Later in the morning I was feeling better, so I decided to settle this question once and for all.  The true cost of riding a bike needs to take into account fuel (I eat more if I bike to work), maintenance (I'm no bike mechanic), and depreciation (I've worn out several bikes in my years as a bike commuter).  This column is a summary of my findings.

I decided to compare bike commuting with driving our nice new (2003) Honda to work and parking for free in the neighborhood.  This is kind of a best-case scenario, stacking all the odds in favor of the car.  But it's a realistic scenario; I don't think I'd be able to stomach actually paying for parking in the company parking ramp, and some of my coworkers manage to find neighborhood parking every day, so that's most likely the choice I'd make.  My wife probably wouldn't be happy being stuck driving the 1974 VW Beetle to all her appointments, but if I were to car commute I would be the primary driver of the family, so taking the Honda would make the most sense.

The most difficult calculation to make is fuel.  Just how much more do I spend for food when I'm biking?  From standard charts I determined that I expend about 1,000 calories a day biking the 28-mile round-trip to work.  I know I eat a bigger breakfast when I commute (call it one extra bowl of cereal:  220 calories, $0.40), that I get a snack more often mid-morning (call it a piece of toast with butter and honey:  250 calories, free), and that I have a handful of dried fruit and crackers before I head home in the afternoon (270 calories, $0.50).  Adding all that up comes to only 740 calories.

Since I'm not slowly wasting away to nothing, I guess I must eat a bigger dinner at home when I bike.  I dug out a bunch of grocery bills from the recycle bin, added up a month's worth, and divided by the number of calories our family most likely consumes in a month.  Result:  $0.002 per calorie.  Multiplying that by the remaining 260 calories comes to $0.52, resulting in a total daily operating cost of $1.42, or about $0.051/mile.

As I write this, gas is down to about $2/gallon.  So driving a 35-mpg car costs about $0.057/mile.  Not much more than biking!

Next is maintenance.  As I mentioned already, I'm not much of a bike mechanic.  I can change a flat tire, oil my chain, and even change my chain once in awhile (I try to change it every thousand miles), but I couldn't true a wheel or keep my disc brakes in adjustment if my life depended on it.  So I have to take it into a shop several times a year to get it whipped back into working order.  And eventually pretty much everything wears out.  I've had to replace my rear wheel and drive train many times in my eight years of commuting.  What does this cost?

Fortunately I keep all my receipts.  It was a simple matter to add up all the costs on my bike since I bought it in May 2005.  Result:  $975.  Divided by my total mileage over that time (14,500 miles) the average maintenance cost is $0.067/mile.  Working the same calculation on our 2003 Honda resulted in a maintenance cost for the car of only $0.042/mile.  The car wins!

It's not looking good for my bike commute.  Only depreciation is left:  will that be enough to rally it to victory?  In short, yes:  the capital cost of a bike is far less than that of a car, even when taking into account the fewer miles that a bike typically covers.  Here are the details, taking straight-line depreciation based on how long my previous bike and my previous Honda lasted:

Purchase cost$17,500$700
Expected life span140,000 miles20,000 miles
Cost per mile$0.125$0.035

The bike is much cheaper to purchase. That's really where the win is. So here's the summary:

Operating cost$0.057/mile$0.051/mile

Not exactly a slam-dunk for bike commuting, is it?

It's never been about the money for me. It's about the fresh air, the exercise, the escape from the rat race. It's nice to know I'm saving money, too — a little money — but I'd still be a bike commuter even if it came at a premium. So next time someone exclaims about how much money I must be saving, I've got the data to set them straight. But I probably won't. I'll just smile and nod.