I like Jenssen's approach best. There's too much power loss with each DC/AC and AC/DC conversion.

About 7 or 8 years ago, before I moved everything to the cloud, I had a small 6-server farm. My electricity bill made it impractical to keep it running.

I approached a company that makes PC power supplies and asked about the possibility of creating a 12 VDC input to 3.5/5.0/12.0 VDC regulated output with standard PC wiring harness. They only wanted to entertain the idea of creating such a thing if I was going to be ordering several thousand units.

Seems like the big server farms should be situated in cloud-free high-altitude (cold air) deserts, using that type of super efficient power supply.