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.
At idle, both cards are consuming 19 watts of power. This rises to 111/112 watts for the HD5830 and HD5850 respectively. Under Furmark load this rises to 145/150 watts.