I know the mac pro isn't exactly energy efficient but I do tend to leave my computers on for prolonged periods idling. Someone mentioned in another thread that the Mac Pro has a 1000W+ PSU. Typically, how much are you eating up if you're running the 2.8Gz, 8GB Ram, 2 drive with the stocked 2600XT? Assuming no number crunching is being done. The energy bill came in this month and it was over $300.