How to reduce power consumption on 5 server PCs?

Question

Server equipment

There are 5 server PCs at home, they work in the background with the necessary software.
No, not a farm.
Everyone has their own monitor, I cut down the monitors after launching the necessary software and that's it.
Everywhere Win7. Who will advise what?
The total number of watts is approximately 3000w if you look at the power supplies.
the bill came to 6000 this month ... the wife almost threw everything out the window) I will
also add that the percentage works by almost 60-70%, the RAM is just as busy.
Video cards do not work (not needed)

Answer 1

Rebuild on energy-efficient hardware, use virtualization, disable all desktop services in Windows (such as indexing, defragmentation, auto-updates, aero themes). In general, it is better to use server Windows - it does not waste CPU time on graphics.