Thank god, people are at least thinking about this and what the hell to do.
We, my family, are probably pretty well screwed. We live in the country, but not far off is a semi-major city. Maybe 20 miles. We live in a subdivision. Water's not a problem. It's food. We are shopping week to week and entirely dependent on Food Lion being open and accepting the bank card. We might go to my dad's, 30 minutes further into the boonies in farm country. There's woods and a fireplace, a hand-pumped well(it runs off the electric pump, too, but in a pinch...) The issue of stockpiling food will be the issue. I want to prep a little, like a few months "food" if you call wheat, rice, beans, and seeds "food". the first winter would be harsh. Our loved pets might become several dinners, to be honest. (6 cats and a 200 lb. st.bernard that's all bark)
Sounds bad, I know, but there would be 9 of us in that little house(2000 square feet including the basement), and I can lose weight, the kids, 3 to 16 can't. I'd offer to trade labor to local farmers for food in any way I could, but there's limits to that. They have to eat, too.
As far as the "which event" discussion goes, here's the issue: once the government has run out of steam, who's going to go to work to keep the power on, even if we're talking nuclear subs at pier side?
If they have to repair everything, as the OP said, then we're thinking something to cause an EMP type event. There was an old cold war plan by the russians to use a nuclear explosion to create an emp over the middle portion of the US to knock out electricity and communications as a prelude to nuclear war. The idea is that if it's capable of carrying electricity, the EMP induces a voltage in the wires.
Think about that for a second. It doesn't matter that the computer is off, or that your phone was in your pocket. Everything electronic just blew it's capacitors. It's not just transformers that go on the grid, either, but the computers that control it, the machines with chips to make the right crap to make a transformer is gone. 90 days? pfeh. Maybe if the federal government picks one state on each coast and one in the grain belt and focuses everything on getting those three sites up and running. Do you think your house is on their list of places with "urgent need" for electricity?
A further complication, whether this is nuclear, solar, or otherwise, what if the political leadership is taken out in the process? Now you have Joe Bumbleduck claiming power, as well as the new (necessary) local communities who try to band together and arm themselves, as well as the jerks with guns and no morals, as well as any lower level government forces, police, etc trying to get together somewhere.
We lose the grid for more than a month, especially mid august, you're talking about frontier life in the 1800's fast, probably with a healthy dose of small-scale warfare, depending on the reasoning capacity of the biggest jackanapes in charge.
I'd love to think we'd all file in nice and orderly to the city and someone would hand us MRE's over the course of a year and take "volunteers" to try to fix the grid and make transformers by hand. I just don't have enough faith in my fellow American, whoever he may be.