Usage without load
An efficient power supply helps reduce your power bill. What's even more important is that a PSU doesn't use much power when the PC is turned off, and that is why we always perform a test without load. We do this with the PSU turned on and turned off, except when there is no on/off switch.
We measure 0.061 and 0.078 watts, respectively, which is a very good score for the Be Quiet Dark Power Pro 10 550W.