Here we see two power traces recorded with a Watt up? Pro ES and the real-time software add-on. The orange line shows the system powered down where it draws 1.7 watts, then booting and finally during a run of PCMark Vantage's System Test Suite. The test finishes, but doesn't go back to where we measured idle power at right away. At idle, the system consumes around 122 watts.
The black line shows a run of 3DMark 11 in the Fire Strike test set to Extreme and with a resolution of 2560x1600. At peak while gaming, the system consumes around 660 watts of power.
It is possible to push the system higher with synthetic loads, but I don't feel the methods used are appropriate for finding the real-world power consumption.