Carbon Footprint: Transportation

Transportation is the biggest emitter of CO2 in most American families. Here is our transportation carbon footprint estimation.

We have two fairly efficient vehicles: a 1997 Ford Escort, and a 1998 Honda Civic. We also have a 2001 Suzuki GS500 motorcycle as a spare vehicle.

To estimate our usage, I looked at when we bought each vehicle, and how much miles we have put on them.
Ford Escort purchased in 2004 at 120,000 miles. It has now 235,000 miles, so that is about 20k miles per year.
Honda Civic was purchased in early 2008 at 145,000 miles. It has now 193,000 miles, so about 20,000 miles per year.
Because we moved closer to work, I reduced out estimated yearly mileage to 15,000 miles per vehicle per year. The estimation is conservative, my commute was reduced from 28 miles to 18 miles, 35% reduction, but I applied a 25% reduction for both vehicles.

We can now estimate how many gallons each vehicle uses per year:
Ford Escort gets 33MPG, or 454 gallons per year (15k miles).
Honda Civic gets 37MPG, or 405 gallons per year (15k miles).
Note that the MPGs are average, measured by myself, not advertised mileages.

Our total gasoline use is 860 gallons per year.
At 8.8Kg of CO2 per gallon, that is 7.5 tons of CO2 per year.
The average American family emits 12 tons of CO2 for transportation (and another 12 tons for household operations), so we are about 38% lower than the average.

Since this blog is about Carbon reduction, lets see how much we can reduce that, and for how much money.

The Ford Escort as a newer engine in it (100,000 miles), so we can keep this vehicle for when we want to haul cargo or people.
For my commute, I can use my motorcycle, and I can replace my Civic by a hybrid for bad weather. My wife may use the hybrid when I use the motorcycle.

Here is an estimation of each vehicle mileage for a year:

Suzuki motorcycle = 10,000 miles at 70MPG = 143 gallons per year.
Honda Insight = 15,000 miles at 70MPG = 214 gallons per year
Ford Escort = 5,000 miles at 33MPG = 151 gallons per year.
Total = 500 gallons per year, or 4.4 tons of CO2, a reduction of 3 tons.

How much that reduction would cost us?
A used Insight costs about $7k.
Payback would vary with gasoline price:
At $3/gallon, 6.5 years
At $4/gallon, 4 years 10 months
At $5/gallon, 3 years 11 months ~ 4 years.

One important point is that the Honda Civic will need replacement soon, so considering the full price of the Insight is not a fair calculation. Instead, I should compare how much I would pay for a non-hybrid vehicle, about $3500 for something like a Cavalier, so the true cost of the hybrid system would be $3500 for my case. This would put the payback time at:
3 years 3 months at $3/gallon
2 years 5 months at $4/gallon
2 years at $5/gallon.

From this data, I can decide how important changing vehicle would be on the priority list. Initial capital investment and payback time are the prime drivers, since future savings will pay for coming projects.