I used an 80plus platinum certified atx psu for my home Controller pc. This machine is a 6 core heavy computing setup and is also always on. On idle I used approximately 80 watts and max load was 125watt. I wanted less power consumption without having to buy a new pc. Read on for my solution.
Step 1: Remove Old AC Powered Atx and Install DC Powered Atx.
Notice the m4 atx is in an enclosure specifically made for it. All of this from Amazon.
Step 2: Solar Efficiency and Excellent Completion.
You must note that I power my pc from my solar battery bank of 25.6v. If you use a AC DC adapter then your efficiency will not be as high but should be higher than most atx supplies.