my city required me to get an 18k generator to be installed as whole house. Absolutely ridiculous amount of power.
After one power outage and running extension cords all over the house, while trying to teach my wife how to get this set up and running, I said this won't work. We now have a 10 circuit generator bypass panel wired into the main panel. I wired it for 30 amps, essentially 7500 watt generator, but only have a 5500 watt generator.
It's really easy now, she pulls out the generator, plugs it into the wall, starts flipping switches. 6 of 10 are green circuits, all can be turned on. only one red from each side can be turned on, and that's only long enough for the start up load to settle down. The highest running load I've seen is a total of 3,000 watts, and that included while the furnace (A/C not wired in) was running.
If you're going to get a gas unit, please please please get non ethanol gas and use a stabilizer. I run aviation gas in mine, that stuff is good for decades.