According to my Kill-A-Watt it is using 1 Watt. If that is correct it will cost me about $1.34/year to run the Obi.
I have my UPS connected to the Kill-A-Watt and it says I am using 18 watts. I use the UPS for phone backup so I have the Cable Modem, Obi 100, portable phone base station and Asus Modem connected to the Kill-A-Watt and it says I am using 20 watts.