Honestly, you’d need a pretty big generator. In cold weather, you need at least a 2-3kw of power to warm the battery in cold conditions. Then, you’d be left with whatever extra headroom you have from the generator to charge. So, a pretty big 4-5kw generator might get you 1-2kw of charge per hour.

A Model Y has a 72kwh battery, so you’d probably get about 2-3% an hour. (3-6 miles of charge per hour)

When doing road trips, superchargers are typically every 50-100 miles, sometimes a bit more. Route planning in the car does a pretty good job.

I’ve only ever had one leg of a trip feel sketchy. It was when I picked up a friend from an Air Force base out in the middle of nowhere Texas. 1.5 hours out and back to the nearest supercharger. Took about 85-90% of my charge.