An energy-efficient refrigerator consumes energy at the rate of 280W when it's actually running, but it's so well insulated that it runs only about one-sixth of the time. You pay for that efficiency up front: It costs $950 to buy the refrigerator. You can buy a conventional refrigerator for $700. However, it consumes 400W when running, and it runs one-fourth of the time. Calculate the total energy used by each refrigerator over a 10-year lifetime and then compare the total costs--purchase price plus energy cost--assuming electricity costs 10 cents per kilowatt-hour.