With specific attention to national electricity power grids.
Some pertinent details needed to answer the question might be.
- What parts of the power grid get damaged by such an event
- How do they get damaged
- How quickly & easily can damaged components be replaced
- What is the expected effect on nuclear power plants.
I suspect myself that other than potential meltdowns of the nuclear power stations this is probably all fixable in reasonably short order?
Here's a Quora answer to some of those questions, one of my first Google hits, I don't know how accurate it is but it ties into my suspicion it's a less than fall-of-government worldwide apocalypse scenario.
My own suspicion is it's likely the fried components can all be replaced within 12 months & aside from any loss of electricity production capacity from the loss of nuclear power plants to meltdowns when their monitoring & control systems got fried everything would be more-or-less back to normal by then.
Naturally I'd also expect a decade or more of increased brown-outs caused by the loss of any nuclear power plants that went into meltdown while replacements where built.
You just have to look at Chernobyl to know that a few nuclear power plant meltdowns aren't going to cause an apocalypse either, just provide us with a few really good nature reserves most poachers will be less than enthusiastic about going into.
Howsoever, my own knowledge of the appropriate technical terminology to generate suitable search results in Google & elsewhere to confirm or disprove my hypothesis to my own satisfaction is it would seem sadly lacking, so I've come here for an answer.