The DC connector on the back says 12V/5A so the maximum power draw would be 60W. It is likely less than that. Plug it into a kill-a-watt if you need something more accurate.
That information can be found here : ( http://community.etcconnect.com/wikis/products/knowledgebase-how-much-energy-does-a-smartfade-consume.aspx )
"The Smartfade is very energy efficient. It's average energy consumption is 8 Watts and peak consumption is 15 Watts.
If the user is looking to replace the power supply, please follow these guidelines:
800mA 12V AC/DC to 1.2A 12V AC/DC peak. 15V DC max. 12V AC max. Input is AC or DC capable. The unit will work directly from a step-down transformer with 9-12V AC output."
