$8/month

I got a kill-a-watt from Newegg.com to measure how much energy my computers use when I leave them on all of the time. So far I have measured 2 computers. Both are Athlon XP single cores (3200 and 3400) with integrated video (crappy Via Unichrome and GeForce 6100). So far both use around 60-65 watts when idle and up to 100-120W when I make them work really hard. It's not as bad as I thought it would be. It does make me wonder how much power an Atom based system would use. At about 70W running continuously that makes about 50KWH for a month. Doing some quick calculations tells me it costs me about 8 bucks a month to leave it running.