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 12 hours per day for 6 months of the year, how long does it take to recover the $100 extra cost?

You would save

$0.05⁄hour × 12 hours⁄day = $0.60⁄day

Six months is about 180 days, so in the first year you would save

$0.60⁄day × 180 days = $108

Spending the extra $100 for the Energy Star unit actually saves you $8 in just 1 year of use. In 3 years of use, the savings will more than pay for the entire initial cost of the unit (3 × $108 = $324), and after that you pay only for the operating 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 watch TV an average of 4 hours per day.