Since our power-usage benchmarks are relatively new, we don't have data from the E8500 machine to compare to the Q9550 system. However, we do have the i7 920 system's power draw to look at.
To quickly recap the way we measure, the first Active Idle test takes place when the PC idles in Windows, and is not hibernating or in sleep mode. The next test involves running the CPU at full load and using the Prime95 CPU stress testing program, which is set to calculate small FFTs (fast Fourier transform). GPU load is measured during the Perlin noise test in 3DMark Vantage, as we found it to be the most power-hungry test in the suite. And of course, CPU and GPU load is run using both of those tests simultaneously.
Remember that the i7 system has a less demanding video card, so that greatly influences the results of this test. What we want to concentrate on are the idle and CPU power draw numbers.
Idle power draw is very close, which probably demonstrates the improvements that Intel's power-saver technology offers the i7. However, under CPU load, the Q9550 looks like a strong alternative to the i7--its peak overclocked CPU draw is less than the i7's stock CPU draw. This is something to keep in mind if you're building a system designed to maintain a constant workload.