Tablo consumes about half the power of a standard cable company set-top-box.
While consumption varies slightly between the 2 and the 4-Tuner Tablo units, the average is as follows:
Low Power - Idle state (no active recordings, nothing being watched) = 9.2 Watts
Max Power - Normal Use (4 active recordings, 1 channel being watched) = 15 Watts
These figures do not include the power consumed by attached USB hard drives.