The most significant feature of the ZM850-HP Plus is, without any doubt, its cooling system that utilizes a dual heatpipe heatsink for silent operation. Indeed even with over 50°C ambient and at full load the cooling fan worked silently enough, at least for my ears. Despite being specified officially to 40°C operation, over-temperature protection did not trigger during our 50°C+ testing, which that means that the secondary heatsink's temperature was not getting too high. In addition, efficiency throughout 20-100% load range was at good levels, ripple suppression for all rails was very good and the overall performance of +12V, the most significant rail in a modern system, was excellent at all times.

The biggest drawbacks I spotted were the performance of 3.3V in the 2nd Advanced Transient Response test and the huge length of the PSU that will render it incompatible with many PC cases. The third and most significant drawback of this PSU is its sky high price since it costs 200$. At this price tag you can find many PSUs that may not be as silent but perform as good or even better and have the higher 80PLUS Gold efficiency so its really hard to recommend such a pricey PSU, even though it has really low noise levels, is semi-modular and can support up to three hi-end graphics cards. Unfortunately, it is the normal that "silent" products come at a price premium, Zalman's ZM850-HP Plus is no exception.