The math behind carpooling
Image via Wikipedia
Everyone knows that carpooling saves you money. But the question is, how much money? Here’s the math behind it.
Assume your car gets 20 miles per gallon. If you carpool with one other person, that means you drive half as often, which means you spend half as much money on gas. If you drive 20 miles each way to work, each day you don’t drive saves you two gallons of gas. At the current price of gas, you’d save about $5 per day.
26 weeks out of the year, you drive 3 days, the other 26, you drive 2 days. That’s an average of 2.5 days per week; 52 weeks in a year works out to 130 days you weren’t driving; multiply that times the $5 per day you’re saving on gas, you’re spending $650 less on gas for the year.
Of course, that means that if your car gets lower gas mileage, you’ll save more. The equations actually look like this:
[tex]\textit{gallons per day} = \frac{\textit{miles per day}}{\textit{miles per gallon}}[/tex]
[tex]\textit{savings per day} = \textit{gallons per day} * \textit{cost per gallon}[/tex]
(261 is the number of “business” days, not excluding holidays)
[tex]\textit{days driving} = \textit{261} – \frac{\textit{261}}{\textit{1 + passengers}}[/tex]
[tex]\textit{yearly savings} = \textit{savings per day} * \textit{days driving}[/tex]
or
[tex]\left(\frac{\textit{miles per day}}{\textit{miles per gallon}} * \textit{cost per gallon}\right) * \left(\frac{261}{1 + passengers}\right)[/tex]
So, solving the equation for a car that only gets 10 miles to the gallon:
[tex]\left(\frac{\textit{20}}{\textit{10}} * \textit{\$3.00}\right) * \left(\textit{261} -\frac{261}{2}\right)[/tex]
[tex]\left(\textit{\$6.00}\right) * \left(130\right)[/tex]
[tex]\textit{\$780.00}[/tex]
That 10 mile per gallon car, if carpooling, now saves you $780 per year in gas. And the number goes up if you can get more people carpooling:
[tex]\left(\frac{\textit{20}}{\textit{10}} * \textit{\$3.00}\right) * \left(\textit{261} -\frac{261}{4}\right)[/tex]
[tex]\textit{\$1174.50}[/tex]
4 people carpooling means you spend almost $1200 per year less on gas. That’s a good vacation with the family!
Related articles
- How to green your commute: Carpooling and public transit (mnn.com)
- the more the merrier. (geteconow.com)
- The Best Cars for Carpooling (mint.com)
