# How to Calculate Energy Savings of Carpooling

by Rogue Parrish, Demand Media

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Energy savings are part of a bigger picture of the benefits of carpooling, which also saves you costs related to parking, tire replacement, depreciation, tolls and maintenance. Sharing a ride saves you an average of almost \$900 a year, estimates the South Carolina Department of Health and Environmental Control (see References 1). Calculating your energy savings requires looking at fuel saved by sharing your ride.

Step 1:

Drive to work and calculate the round-trip mileage by recording the beginning and ending mileage from the odometer. As you drive, survey prices displayed at gas stations to come up with a rough average of the current cost per gallon of gasoline. (See References 5)

Step 2:

Determine your vehicle's miles per gallon based on online estimates from the U.S. Department of Energy and the U.S. Environmental Protection Agency, or your own tests of how many miles your car clocks per gallon (see References 2).

Step 3:

Multiply your daily mileage by 21 to arrive at the typical number of commuting days per month. For example, if your daily commute is 10 miles round trip, you commute 210 miles a month. If your car gets 30 mpg, you use 7 gallons of gas per month commuting, or \$28 if gas prices are at \$4 per gallon. If your own car stayed parked while you carpooled with another person, your energy savings are thus 7 gallons or \$28 per month. (See References 5)

Step 4:

Account for greater overall savings if, for example, you drive a compact, fuel-efficient vehicle and your friend leaves an SUV-sized vehicle parked the entire month. In the scenario of 210 commuting miles per month, energy savings can be 14 gallons, or 210 miles divided by 15 mpg. If you add a third person to your group, the energy savings are likely to be an additional amount between 7 to 14 gallons, depending on the precise mileage figures of the cars kept off the road by carpooling. (See References 5)

#### Tips

• Even if you carpool only one day a week, you can reduce your gas consumption for commuting by 20 percent. (See References 4)
• Online calculators can immediately figure your energy savings if you enter your parameters on commuting distance, commuting days per month, miles per gallon and number of passengers. (See References 5)
• To calculate the overall cost savings of carpooling, factor in as well what you pay per month for parking. Add in the costs related to maintenance and tires, which, as of the time of publication, AAA estimates at 5 to 6 cents per mile, depending on the size of your vehicle. (See References 6)