Suppose that the new type of computer power supply described in Problem P7.31 costs an additional $5.

(a) At the cost of 12¢ per kW ? h, after what period of time would the cost savings in electricity offset the power supply’s added cost?

(b) How often do you estimate that individuals and companies generally upgrade their desktop personal computers?

(c) From an economic standpoint, what recommendation would you make regarding the new type of power supply if you worked for a computer manufacturer?

Problem P7.31

When a desktop personal computer is operating, its power supply is able to convert only about 65% of the supplied electrical power into the directcurrent electricity that the computer’s internal electronic components require.

The remainder of the energy is mostly lost as heat. On average, each of the estimated 233 million personal computers in the United States consumes 300 kW ∙ h of energy each year.