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 size difference. The m4 atx supplies 250 watts max at 94percent efficiency. The 12 volt cpu connector is a single 4pin plug which is good enough for my setup. I need 12V and 5v for my home automation and communications devices so I pushed out one molex plug for this purpose.
Notice the m4 atx is in an enclosure specifically made for it. All of this from Amazon.
Step 2: Solar Efficiency and Excellent Completion.
The first pic is maximum load whereas the second is idle. The pc and attached devices consume approximately 30 watts less at idle and 20 watts less at maximum load.
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.