Noise levels
Noise levels were measured at idle and under load using an Extech 407727 Digital Sound Level meter placed 1" from the rear of the system and out of the direct path of airflow. You'll notice "missing" results for some of the PSUs at idle. We've omitted them because our meter only registers noise levels above 40 decibels, and most of the field is quieter than that at idle.

Some of the PSUs are louder than 40 dB at idle, though, including models from ThermalTake, Antec, and OCZ. The picture changes somewhat under load. For instance, the GameXStream moves from last place to middle of the pack, and the Earthwatts ranges from under 40 dB to over 54 dB. The Corsair HX and the Silencer 750W stand out in both cases, though.

Power consumption
Power consumption was measured at the wall socket for the entire system, sans monitor or speakers.

14 watts separates the most efficient PSU from the least at idle, with the Neo HE, Silencer, and HX rounding out the top three. The Toughpower is the least frugal at idle, consuming four watts more than the next closest model.

Under load, the gap between the most and least efficient PSU shrinks to only seven watts. PC Power & Cooling, Corsair, and Seasonic round out the top three, but they don't enjoy much of a margin over the rest of the field.