I believe the most interesting aspect of this series is the fact that on the face of it the "event" can be based in fact... not fiction.
Do folks have such little understanding of Electricity, that the underlining premise of this TV fictional show will actually permeate via propaganda and will become fact to a wide proportion of folks who watches such nonsense?
There was rapid progress that was made when the main components of the modern electrical world, such as electricity generation and transmission were invented in the UK by Faraday (Electric Dynamo and Transformer), James Bowman Lindsay (Electric incandescent light bulb) James Clark Maxwell, David Edward Hughes (Radio Communications) etc, even without a previous industrial base for this technology. Would these discoveries by lost forever by today's society?
An electrical grid black start would be problematic but not impossible to bootstrap back from.
Is electricity such a mystery? Everyone must know how a simple electrical circuit is built and works. It was taught to everyone at School. There are folks known as Electrical Engineers still around!
There are even many folks in the USA who can even rig up a Generator to provide electrical power for their homes every other 6-12 months when there is some poor or wet and windy weather.

If the lights do go out over an extended period, it would probably be more likely that the majority of folks couldn't afford to switch them back on again rather than a HEMP.
http://www.youtube.com/watch?v=EeNOjbvA74g