5500 watt (11HP or 340cc engine) is about the right size for most homes. "IF" you can manage your loads (wife and kids behave)
1) it will run a 4500W water heater
2) it will start and run a 2hp well pump
3) it will run a burner on a cooktop easily
4) it will run household lights
5) it will start run 2ea 10,000 BTU air conditioners
But, it won't do all of the above at the same time. Still, it's very likely to be the right choice.
ALSO!!! I don't like enclosed generators. I like top tier, contractor grade, non inverter, robust, easy to repair, open frame units. Honda, Northern-Tool, Yamaha, etc.
I don't like the cheapies from China, such as Briggs, Chonda, homeless depot and lowes models.
Suggestions:
4500W
http://www.northerntool.com/shop/tools/product_200467313_200467313
6600W
http://www.northerntool.com/shop/tools/product_200467366_200467366