So how much does a desktop computer cost to run 24/7? (About $1 per day)

I could put on my engineering hat and say "it depends", which would be a typical Geek answer, because it does depend on a lot of things. However such an answer is not very useful to most people.

I can tell you that my #1 suspect in increased power consumption was my work PC, a Compaq Evo D500 desktop of mid-range performance (circa 2001 -- what can I say...my employer is thrifty), with dual 19 inch displays (Dell LCDs). After several months of monitoring, I can tell you that in round figures my PC and displays pull about 200 watts idling and 300 watts running full tilt. The cost per day is $1.06 on average, or about $32 per month.

By the way, the PC is left on 24/7, but does not sleep. The LCDs go to sleep after 5 minutes of lack of activity, and the hard disk spins down after 15 minutes. I'm at my work PC about 10 to 12 hours a day.

So are you shocked at how much leaving a PC connected costs these days? I certainly was. To put that in perspective, it represents 10% of my total power bill on a bad month, and 15% of my average bill. Don't let someone tell you keeping a computer on 24/7 doesn't cost much!!

Similar tests on server class PCs running 24/7 were even more discouraging. The typical power consumption was about 400 watts per hour, or about $1.75 per day.

So now that I know, what can I do about it? To some extent, not much. Several applications I have need to run 24/7 so it isn't a good target to shut down entirely, but I do unplug things over the weekend and on holidays. (Every little bit helps). The real answer may lie in upgrading to more modern equipment. Future Greener Geek measurements will tell all !