So I'm reading some spec sheets, trying to figure out whether to buy more 750W Titanium power supplies or some more 495W Platinum power supplies, given that my servers idle around 70W-80W most of the time. Well, reading over dell's spec sheet, I stumble across the following odd bit of information:

auto-ranging Platinum efficiency 495W, 750W or 1100W AC power supply;

So I did the math based on 10% load on the 750W Titanium, and took a conservative estimate of 88% efficiency on the Platinum 495W, and concluded that the best I could get was equal efficiency, and probably wouldn't hit that, so my 750W titanium are probably better, but it's not worth rushing to migrate all PSUs to the same titanium model.

However, one thing still confounds me: What is this 'auto-ranging' thing in the specification? What does it mean in this context? Is it just marketing speak, or is it meaningful somehow?