Be Quiet! Dark Power Pro 850W

Results

As you can see below, the outputs from the Dark Power Pro 850W are very good. There are slight dips in the 12V rail when heavily loaded, but it's not of serious concern, and the full loading on the 3.3V and 5V rail is very impressive.

The efficiency is consistently very high at 88 percent at 50 to 75 percent load, 85 to 86 at full load and a high 84 percent at 20 percent round things off nicely. With that said, the 650W produced marginally better results on average - more so at full load. Just like the 650W though, it's the quietest 850W we've ever tested as even when the fan hits about 75 percent speed and it's still extremely quiet. Not actually silent like the 650W, but even in the quietest, watercooled setup needing a 850W PSU, you'd never hear it. While clearly fantastic, in that sense of the hardware it'll be paired with - is it also over the top?

Things got a little hot under the collar though as the 850W kicks out more heat at a respectively lower efficiency than the 650W, so internally we measured temperatures of 62°C on the main transformer - usually one of the hottest parts (depending on topology) - and a general 50°C internal temperature with an exterior base temp at a considerable 40°C.

We'd recommend avoiding using this PSU where the fan sucks air straight off a hot CPU heatsink - instead going for a case where it's in the bottom or at least there's a side fan for some more immediate ventilation. We brought up this concern with Be Quiet! and it said it's aware it runs "a little hot" but the technical consultant at Listan (the parent company) dismissed is as an issue citing the internal components were rated to at least 85°C and the main transformer will take up to 120°C.

That said, we tested the Dark Power Pro 850W at full load for 30 minutes and it consistently retained the temperatures above without spiralling out of control so at least the fan can cope with the heat produced by the unit, and this scenario is highly unlikely in everything but Folding@Home rigs which are consistently under very high load.