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.
The Gigabyte HD6770 Silent Cell only consumes 16 watts of power when idle and this rises to 93 watts when gaming. It is an efficient design, much like the rest of the HD6000 series from AMD.