I think it would take about 4-7 days before the people go Lord of the Flies if the nation’s power grids were taken down. Watch “The Mist” for a great narrative on what happens to people when you shut off the lights and take away the rules.
**when you shut off the lights and take away the rules.**
Depends if the lights go out in summer or winter. In winter people will be more likely to hunt warmth. In summer, especially a heat wave, look out!