Principles of Environmental Science 6th Edition by William Cunningham, Mary Cunningham

Exercise 7

Personal Energy Use
For many college students, a car and a computer are life essentials. Suppose you were to buy a very efficient car, such as the Honda Insight, rather than a sport utility vehicle, such as a Ford Excursion. How much energy would that save, and how long could you run your computer with that energy?
These calculations are not hard, but you'll need some key numbers to start with:
1. A Honda Insight gets about 75 mpg, while an Excursion gets about 12 mpg.
2. A typical American drives about 15,000 miles per year.
3. A gallon of gasoline contains the equivalent energy of about 3,400 kilowatt-hours (kWh).
4. A computer uses about 100 W of electricity.
Use the previous numbers to figure out the following:
How much gasoline would you save in an Insight, compared with an Excursion?
a. Excursion:
15,000 mi/yr
12 mpg = _____ gal/yr
b. Insight: 15,000 mi/yr
75 mpg = _____ gal/yr
c. Gasoline savings (a ? b) = _____ gal/yr
d. Energy savings: (gal × 3,400 kWh) = _____ kWh/yr