That is more than half my whole houses "idle" use..
So you can see from above, at night - that was 00:48 whole freaking how was drawing 389 watts. Your Computer is 65% of that WTF dude???
That reading is with my workstation on 24/7 (does not standby) plus my N40L server (only draws about 55watts idle) Plus all the other electronics in the house all on, 2 DVRs, slingbox, 3 different network switches. Prob the 100 watt bulb on the porch on? Prob left the living room lights on (cfl so low usage).. Not counting all the phone chargers, laptop chargers, etc.. etc.. clocks, TVs still draw even when off, etc.
I am into saving power as well.. Reason I went to the N40L running even my pfsense router now virtual. Was running 2 boxes before both drawing around 60w idle -- move to the N40L cut it in half for sure.
Have not put my killawatt on my I5 workstation lately - but if recall it only drew like 70 something idle (monitor off).
Wish I had some advice for you -- but I wish you good luck in your quest.. Going to check my workstations idle when I get home, might have to bring back standby atleast at night, etc.
I wish my house used that much when everything was idle.. I'm at 733 right now idle... 250 of that of course is the PC sitting here not doing much at all... that leaves 483 watts in use...
here is where I want to cry... not one light is on in the house... not one tv... that 483 watts is because of vampire crap... 120 watts of it is the AC unit outside's "Crankcase heaters" which run all the freaking time unless the ambient temp is 80 degrees.... so much for enegy efficient... the rest I've tracked down to stuff like the fridge, which is high efficiency (apparently), the TED itself uses 1.5 watts... which isn't much when the fridge isn't running the idle wattage in here goes down to about 375? I can't remember exactly... here's my past hour graph... you can see the different compressors and stuff turning on if you look at it and running... for the fridge... crankcase heaters outside on the ac ect...
every light in our house is CFL or LED... when I tell people how much wattage the houes uses the first thing they tell me to change is the bulbs, well been there done that... and we never have the lights on!
btw, what energy monitor are you using?