Dime-A-Gallon Worksheet

Month                                     

 

1.  Gallons of gas purchased     ________________      x $0.10  =    $                

2.  Ride-share miles         _____ divided by 100=             x $0.11 =     $                

3.  Air miles                    _____ divided by 100=             x $0.25 =     $                

4.  Intercity bus miles      _____ divided by 100=             x $0.06 =     $                

5.  Intra-urban bus miles  _____ divided by 100=             x $0.30 =     $                

6.  Train miles                  _____         divided by 100=             x $0.15 =     $                

7.  BART miles               _____         divided by 100=             x $0.16 =     $                

8.  Walking and bicycling miles            __________         x $0.00 =     $        0.00  

9.  PG&E natural gas therms               __________                   x $0.085 =   $                

10.  PG&E electricity kW-hrs              __________                   x $0.005 =   $                

To find your total, add items 1 through 10                             TOTAL     $                

 

It’s OK to estimate when you don’t know exact numbers.

 

All formulae give the equivalent of $0.10 per gallon of gasoline for all forms of fossil fuels, based on the energy content of each fuel.

 

The formulae for air, bus, and train travel are based on current average load factors (70% for air, 66% for inter-city bus, 20% for intra-urban bus, 36% for Amtrak, and 50% for BART).  For more accurate results, charge yourself less if your plane, bus, or train was fuller than these averages, and charge yourself more if it was emptier.

 

Ride-sharing assumes 4 passengers.  For 2 passengers, use $0.22 per 100 miles; for three passengers, use $0.15 per 100 miles.

Explanation of worksheet calculations

 

1.  Gasoline – actual fuel use times $0.10 per gallon.  This is gas you use in your vehicle.

2.  Ride-share travel  - when you ride in a carpool or take taxi; you didn’t buy the gas, but you know how far you traveled.  Average US passenger fuel efficiency in 2000 was 22 mpg (Bureau of Transportation Statistics, National Transportation Statistics, 2002 – www.bts.gov/publications/national_transportation_statistics/2002/).  If there are four passengers, 4 x 22 = 88 pmpg, or 1.1 gallons per 100 passenger miles @ $0.10/gal = $0.11 per 100 miles.[1]

3.  Air travel – assumes modern jets achieve 40 passenger miles per gallon (pmpg) at average 70% load factor[2]:

      40 pmpg = 2.5 gallons per 100 passenger miles x $0.10 per gallon = $0.25 per 100 mi

4.  Intercity bus travel – uses American Bus Association (www.buses.org/industry/) 160 pmpg at 66% average load factor[3]:  160 pmpg = 1/4 air travel gallons = $0.06 per 100 bus miles

5.  Intra-urban bus travel – uses Bureau Transportation Statistics (BTS) 4147 Btu/pass-mi and 138,700 Btu/gal, yielding 33.4 pass-mi/gal[4] = 3.0 gallons per 100 passenger miles - at $0.10/gal = $0.30/gal

6.  Train travel – uses Bureau of Transportation Statistics Amtrak 2134 Btu/pass-mi and 138,700 Btu/gal, yielding 65 pass-mi/gal = 1.5 gallons per 100 passenger miles - at $0.10/gal = $0.15/gal.  Amtrak  reports 108 pmpg at 60% LF for Pacific NW route, so (www.trainweb.org/aorta/) 65 pass-mi/gal implies 36% LF (1970 Amtrak LF was 35%).

7.  BART travel – assumes same energy intensity as AMTRAK trains but powered by electricity with 50% LF, yielding about 90 pmpg

      90 pmpg x (0.6 generated from fossil fuels) x (3 fossil fuel-to-electricity conversion) = 1.6 gallons per 100 miles at 0.$10/gal = $0.16

8.  Walking and bicycling – no direct fossil fuel use.  Later refinement could consider food calories

9.  Natural gas - therms x (103 cu ft/10.2 therm) x (1.138 x 106 J/cu ft nat gas) x

(1 gal gas/1.318 x 108 J) x $0.10/gal gasoline = $0.0846

10.  Electricity – kW-hr x (0.6 generated from fossil fuels) x (3 fossil fuel-to-electricity) x

      (3.6 x 106 J/kW-hr) x (1 gal gas/1.318 x 108 J) x $0.10/gal gasoline = $0.0049


[1] For 2 passengers, use $0.22 per 100 miles; for three passengers, use $0.15 per 100 miles.

[2] Airline industry claims average 38 pmpg (www.air-transport.org/public/testimony/display2.asp?nid=870).  BTS year 2000 reports 49 seat-miles/gal domestic and 46 seat-miles/gal international, 71.0% LF domestic and 75.9% LF international (yielding ~35 ppmg).

[3] 2.6 billion miles/498 million gallons = 5.2 mpg = 240 pmpg for 100% LF (average 46 seats), implying current average LF is 160/240 = 66%

[4] BTS also reports average gas mileage for all buses was 6.8 mpg in 2000.  City/highway mpg were not reported separately but presumably vary.  At 5 mpg and 40 passengers, 200 pmpg is possible, implying an average LF less than 20% for city buses.