Legit Reviews

Bwall just sent me this picture asking why desktop PSU's are so large when a server PSU that is 900 W is barely larger than a notebook hard drive length wise and will fit in a 1U server. Take a look at the picture he sent with a 2.5" SATA notebook hard drive sitting on top of the power supply
I think the main reason is desktops have larger and quieter cooling fans with tons of connection options that require multiple daughter PCB boards.

I also think to believe the components in a server based PSU are of higher quality, in order to withstand the high amount of load stress it has to handle.

Judging by the picture I'd say an HP PSU. Another reason why we don't have Desktop PSUs smaller, no demand. In 1U Servers, you can't have such a large PSU. If Consumers told Manufacturers they want smaller PSUs it would happen.

1U Server PSU's generally only output 1 voltage (12v or sometimes 24v) which is then down converted to the needed voltages inside the server. That's why.

They are also incredibly loud.

ATX PSU's are larger in order to keep the noise lower, and allow them to be cheaper to produce; also making a Desktop PSU 1U (even if they could keep the noise reasonable) it wouldn't sell because it wouldn't fit in cases.

That particular unit (they also have a 1200w model, HP that is) outputs 24v and that's it. It's much smaller because it has about 1/3rd of the components inside of the unit, with the other parts being inside the server themselves. It only has to regulate voltage to 24v (+/-5%, which is easier than 12v +/-5%) and filter out any ripple.

It's also a very efficient design (94% efficiency @ 230vAC) so it doesn't need a lot of space to get rid of heat.

As above, the single voltage rail and also the use of small high speed "fat" fans. Noise isn't an issue, whereby consumer PSU's do have to keep noise down. Fans in those give out < 60dB and there's at least 2x in each psu (then there's 1x redundant psu on active standby and there can be a 3rd on higher end 4U and above boxes, especially ones designed for virtualisation as they run multiple servers and must never go down)

well, considering that anything is small and higher quality, they won't be cheap, most of the time, atleast, i see that prices are 4x the value of usual PSU we buy for desktops