We installed ours in 2012, put in a Reliance 10 circuit manual transfer switch. Has 2 240v, 8 120v. So the 240v circuits handle well pump and hot water heater, then we have kitchen circuit with fridge & microwave, lights, living room (TV, internet equipment, lights) back room outlet with mini fridge & small freezer, 2 bathrooms, 2 bedrooms, front room outlet for pellet stove.

What gets used in an outage is living room, back room, fridges & freezer, a couple lights , pellet stove (in winter) and the well pump & water heater (but not constantly). So there is usually only a 40-60% load on the gen most of the time.

Reliance has newer model transfer switches , ours is the older Pro/Tran, I'd go for the new Pro/Tran 2 series as it uses standard breakers, the old Pro/Tran uses proprietary breakers that supposedly can't be replaced. Generac makes good transfer switches as well. Ours is wired to an outside connector that the generator connects to with a 15 ft 240v cable.