What would be the collective impact be to our national electricity consumption, carbon emission, and ultimately $$ savings if we all made a deliberate choice to lower computer power use? Personal computers (PCs) consume about 65 to 250 watts (W) of electricity. It turns out that a screen saver does not use any less power than a full screen, and with LCD screens, we dont need to save the screen from burn in like old CRT screens. It is much better to put a PC to sleep then leave a screen saver on. So, let's consider: What would happen if all US homes put their personal computer (PC) to sleep and turned off screen savers when not in use at night? Given the assumptions below for Case A and Case B, answer the four questions on page 4 as you calculate the energy required in Case A and Case B. You might find useful energy and carbon emission information at bottom of page 4. Assumptions for both Case A and B: There are 50 x 106 homes in the U.S. Each home has one desktop PC; assume all U.S. PCs use 100 W at full power, and only 1 W in sleep mode. Case A: All homes leave PCs always on with screen saver on (full power all day). Case B: All homes put computers to sleep for 8 hours/day.

(3) Given the average cost of electricity in the U.S. is $0.12 per kilowatthour (kWh), how much money is saved Case B vs. Case A? Solve for both: (a) money saved per PC, and (b) total money saved for all U.S. homes

(4) Given that the average CO2 emission for electricity generation in the U.S. (see below), how much total CO2 (in tons) is saved in Case B v. Case A?