The noise your PC makes when processing data does not draw any more current than when it sits at idle.
Umm... I understand the sentiment, and your advice is mostly good. But these two statements are simply not true.
EnergyStar power saving technology has been a part of computer hardware for a while now.
* Monitor power management (MPM) can save $10 to $30 per monitor annually by placing your inactive monitors into a low-power sleep mode.* Computer power management (CPM) places inactive computers (CPU, hard drive, etc.) into a low-power sleep mode, which can save $15 to $45 per desktop computer annually.
Nitpicking! ;^)
How much more money would just turning it "OFF" when you leave for the night save per year?
Don't get me wrong, I use screen savers to, well, save my screen display from burned in ghost images.
That alone justifies the technology, IMHO.
But OFF is the answer, in most home and all non 24/7 business applications.