I really haven't thought much about this, and habitually always leave my PC on, 24 hours a day. Has anyone figured out more or less how much it actually costs, for a basic, and more advanced PCs? Mine is pretty simple, has a 650w PSU, a Q6600@ 3.0Ghz, a simple HDD and a HD4850 with a 24" monitor. The monitor goes to sleep after an hour or so, the PC does some minor energy saving mode (I can't stand the full sleep mode - at least on my previous PC). Even rough estimates, anyone have any idea how much it actually costs to keep it on all the time? And how much of a difference is it from something fairly simple like mine, to a monstrosity of a PC?