We used SeaSonic's Power Angel Power Meter to measure the amount of power our test system pulled from the wall. You'll find three figures below: power supply's maximum rated wattage, peak power consumption under a full CPU/GPU load, and how much the system pulled from the wall when idle, following a fresh system boot.
Think a 1,200W power supply is overkill? That depends on what you're doing. We took the SHIFT on a potential suicide run that consists of loading up the CPU with Prime95 and the GPUs with FurMark, a dangerous combination that you shouldn't run for any length of time. The reason we do it here is to get a picture of an absolute worst case scenario, which turned out to be a peak power usage of 1,131 watts. That's just for the system and doesn't include a monitor or speakers.
At idle, the SHIFT system only pulled 180W from the wall, which is pretty good when you factor in the amount of hardware. One thing to note, however, is that this isn't a silent machine as configured. Whether at idle or fully loaded, the system fans and videocards make themselves aware, though it's quieter than most microwave ovens, if that helps put it into perspective.