HardCoreWare.net posted its results for various power consumption tests on all next generation consoles.
Being the least powerful, the Wii is the lowest consumer of electricity out of the next gen consoles while the PS3 consumed the most power. Another interesting note from the tests is that the Wii uses five times more power when using Connect 24 during idle when not using it. According to the numbers provided by HCW, this means an increase of about $1 a month on the electricity bill.
Included in the article is how much power the systems use while playing games, watching videos, in idle and turned off. Check out the site yourself for the complete results.