http://www.goodcleantech.com/2009/03/its_official_apple_mac_...
"The mini uses only 15W while idling in our tests, and a low 34W while running the CineBench benchmark test. This is the second lowest active score, after the 18W observed on the Asus Eee Box nettop."
Moral of the story: Don't judge power consumption by power supply capacity.