I'm watching American Blackout, a video about a hypothetical nationwide power failure.
It is available from Youtube. About 300+MB, 1:27 hours.
Interesting and it does show a possible response of the entire population, which is not say it will happen this way.
I don't recommend letting very young children see this, unless you are able to explain it to them...
I do recommend adults watch, to see what you may face.
Sadly, the filming was intended to represent "hand-held" taping and it is hard to watch without a degree of nausea.
Also the ending it not realistic with respect to the size of the power loss (ten days and power is restored...).