Zalman ZM600-HP presents efficiency around 84% when you pull between 40% and 60% from its maximum capacity (between 240 W and 360 W). Under other load patterns efficiency was between 80% and 82%.

The noise level from power supply is impressively low and when we went to the extreme of pulling 740 W from it noise level was still only at half the maximum admissible.

It is a good product if you are looking for a power supply on the 600 W range with a modular cabling system.