[quotemsg=20786533,0,1903369]Server PSUs lack the minor rails which are essential to any desktop PC to operate, ...
I won't recommend to my readers getting a used server PSU (or a used PSU in general) which can blow sky high once loaded, since you simply don't know how heavily it was used before. On top of that, server PSUs are meant to operate 24/7, so don't expect to find a lightly used one, ...[/quotemsg]Server PSUs are designed to run hard 24/7 for a decade or so.If it's only a few years old there's no problem, since one can expect the mining operation to last for five years or less.
As for the minor rails those can be covered by a second, less powerful and way cheaper, PSU.
Calculating the benefits of power efficiency a simple figure is that 1% difference in efficiency (between two PSUs) translates to a difference in power consumption by about 1.5 kWh/month when using 1 kW 24/7.