In a long term grid-down situation, first there will be rioting in the streets. If you have any food, you will be defending it, probably against guns. A year later, in America, 90% of the population will be gone and most of the ammunition will be used up. Fighting in armor with swords and crossbows will once again be the main defense.
After a severe solar storm or EMP attack, it will take over two years to manufacture enough transformers to bring the grid back up, probably more like five years. That's five years without refrigeration, air conditioning, or the ability to pump gas. Vehicles may be useless, anyway.
Whoever survives will be living in a whole new medieval era. They will be growing food, keeping animals and defending their cottage. Little villages will spring up and locals will defend their territory together. All the ammunition will be used up so medieval combat skills will again become important. In our novel, Mountain Realm, we wrote an epic adventure about medieval reenactors in the soon coming New Medieval Era.