Thinking clearly about energy efficiency and energy conservation can save you a lot of money in some surprising ways. If you are saving money on your electric bill, you are also saving energy and reducing the emission of pollutants. Consider the purchase of an air conditioner. Suppose you have a choice: an Energy Star unit for $300 or a standard unit for $200. The two units have the same cooling capacity, but the Energy Star unit costs 5 cents per hour less to run. If you buy the Energy Star unit and run it for 12 hours per day for 6 months of the year, how long does it take to recover the $100 extra initial cost? You would save:
$0.05/hour x 12 hours/day = $0.60/day
$100 x 1 day/$0.60 = 167 days
Six months is about 180 days, so in the first year you would save:
$0.60/day x 180 days = $108
Spending the extra $100 for the Energy Star unit actually saves you $8 (net) in the first year of use. In 3 years of use, the savings will more than pay for the entire initial cost of the unit (3 yrs x $108/yr = $324), and after that you pay only for the operating and maintenance costs
Your Turn
You are about to invest in a 66-inch flat screen TV. These TVs come in both Energy Star and non-Energy Star models. The cost of electricity is $0.15 per kilowatt-hour, and you expect to water TV an average of 4 hours per day.

a. The non-Energy Star model uses 0.5 kW (half a kilowatt) per hour. How much will it cost you per year for electricity to run this model?

b. If the Energy Star model uses only 40 percent of the amount of electricity used by the non-Energy Star model, how much money would you save on your electric bill over 5 years by buying the efficient model?

Show your work.