Joulemeter is the software published by Microsoft on 19th may 2010
Joulemeter is the software use for the estimate electricity consumption by your computer or laptop.
I think it is the greatest software because with this you can know how much electricity is consumption by your PC
It estimates the energy usage of a VM, computer, or software by measuring the hardware resources (CPU, disk, memory, screen etc) being used and converting the resource usage to actual power usage based on automatically learned realistic power models.
You can download this software from: http://research.microsoft.com/en-us/downloads/fe9e10c5-5c5b-450c-a674-daf55565f794/default.aspx. It is just 0.76 MB.
The source is taken from the http://research.microsoft.com/en-us/projects/joulemeter/default.aspx. The users are advice to first Read the license given at this website before using this software.