To test power consumption today we are using a Keithley Integra unit and we measure power consumption from the VGA card inputs, not the system wide drain. We measure results while gaming in Crysis Warhead and record the results.
Power consumption is a little less than the last GTX570 card we reviewed, peaking just under 180 watts when gaming. When idling, it demands 24 watts. The Powercolor Devil 13 HD6970 is slightly more efficient as you can see on this page.