In deciding whether or not purchasing a motorcycle is a prudent decision, cost plays a significant factor. Motorcycles often get much higher gas mileage (fuel efficiency) than cars. A common belief is that because of this fact, a motorcycle might pay for itself. I wanted to believe this is true, but after running the numbers, this belief is a myth and is only true in extreme circumstances. I’m recording the relevant equations here so that next time I get the impulse to by a motorcycle, I won’t use cost savings as a justification.
In my situation, my everyday car, the Edscort, gets about 34 mpg highway, 30 mpg city. I don’t think I’ve ever seen less than 30 mpg so I’m going to use that figure as the Edscort’s fuel efficiency. The motorcycles in which I’ve been interested have been around $1500 in cost and achieve about 60 mpg. For simplicity’s sake, I will ignore the cost of insurance, maintenance, and accessories.
The cost, c, to drive a vehicle m miles is given by:
where f is the fuel efficiency of the vehicle in mpg and r is the cost of gasoline in $/gal. The cost savings Δc is the difference in the cost of driving those miles with the motorcycle (bike) vs. the Edscort (car). A negative value for Δc corresponds to money saved.
In order for the motorcycle to pay for itself, the cost savings must be at least as much as the purchase price of said motorcycle, P. That is, -Δc = P, where the negative sign makes a negative cost differential equal to a positive purchase price. The number of miles that must be driven before the bike pays for itself is therefore:
In my case, where the Edscort gets 30 mpg, the motorcycle gets 60 mpg, gas is $3/gal (as of this writing, it’s $2.99/gal down the road) and the motorcycle purchase price is $1500, I would need to drive the motorcycle 30,000 miles to break even. And note, these trips on the motorcycle must be in place of rides in the Edscort, not in addition to my usual driving.
To point out how impractical this is, consider that I’m currently averaging about 10,000 miles per year driven. If I can substitute the motorcycle for 20% of those miles, I’ll put 2,000 miles on the bike per year and it will pay for itself in only 15 years. I could cut that to 6 years if I substitute the bike for 1/2 of my normal driving. Ideally, I’d want the bike to pay for itself in 2 or 3 years, but that’s obviously not going to happen.
New bikes are considerably more expensive and I’ve not considered other ownership costs in which case things get even worse. Of course, reducing the wear and tear on the Edscort might stave off a significant repair bill, but there’s no guarantee that’s the case. Nor is there a guarantee that the bike won’t need a major repair itself.
The bottom line is that cost savings cannot be used to justify the purchase of a motorcycle. The decision to buy one is not a practical decision. Face it.