how to measure watt usage in 24 hours

[fishsauce]

Does anyone know of a way of measuring how much wattage I use or a program that will do it for me? I leave my comp on 24/7, and I need to know how much its costing me.
-Thanks.

[spectra6.0]

I beleive the power company calculates usage by kilowatt hours. one thousand watts per hour x what ever their rate is. So you need to know how much power ( watts ) your computer / monitor consumes .
Check out this link;

http://www.consumerspower.org/home_energy/billestimator.php