Since I have moved from Windows XP to Ubuntu 12.10, I have been constantly blamed for increased electricity bills.(That may be true, but I think the reason is increase in the time I use my computer, because it is more productive now).

Is there any software that would calculate how much power my computer actually uses?

Note that I use a Desktop and the Powertop, Powerstat, and Power Statistics programs referenceed here only work for laptops.
The answer suggests that for desktop the only solution "then" is to use a electronic watt-meter. Has the situation changed in last 2 years?