Not only what you want to run watt wise but what about voltage?
-are you running a well pump, reverse cycle A/C, or an electric stove?
More than likely they will be 240v which requires a 5000 watt unit to start.
-do you want to just run basic necessities like fridge and electronics?
You can get away with something alot smaller without a transfer switch.
I have a Honda EU2000i inverter generator which I used to run an oil furnace (including circulators), fridge, tv, all the lights in the house, etc. without issue on a 5 circuit transfer panel. It was super quiet and ran forever on very little fuel. Plus you have options for bigger tanks that extend your run time. I also had a bigger 5000 watt Honda which I had on a full panel transfer switch. I could run everything except my electric hot water heater. So that meant endless showers (as long as you didn't mind cold water), electric stove usage, and pretty much everything else in the house turned on. Very noisy and drank fuel. That is why I only kicked it on for cooking and showering.
The inverter is portable like a suitcase. The 5000 watt was on wheels and pretty much had to stay put or wheeled around in the yard. Two people required to lift.
