How much does it cost to run a computer?

Here's something that has always hung around in my mind, but I never got around to looking up the answer. How much will running PCs add to your power bill?

Anandtech posted an article where they calculated the cost of running a PC per hour.

* For a middle of the line system, they figured one year of use is $93.51 for 8 hours a day.
* If you let your PC sit idle 24 hours a day, it will cost you $128.12 a year.
* For a top of the line system that is at full load all day long (like a server) you could spend $440.85.

These prices are calculated at the price of electricity in North Carolina. California PC users will pay almost double.