Can't remember. The same channel that does "Doomsday Preppers." And there were a LOT of ads for prepper related stuff like Wise freeze dried food...that sort of thing. I have to wonder if the prepper supply community didn't underwrite the whole thing.
You may be able to find it on Hulu or Netflix or Amazon...don't know.
Okay, it's the NatGeo channel and here is the trailer...
American Blackout (http://www.youtube.com/watch?v=Vi_Rz9mCTjM#)
This is supposed to be a rental link but I've been watching it for a while and it hasn't shut down...
American Blackout Documentary 2013 National Geographic (http://www.youtube.com/watch?v=x6KTH4XwdMk#ws)