Hey fellow Lehigh Valley Disney fan!
We are in the middle of installing a natural gas whole house generator. This is different from a free-standing generator (which I think is what you're looking for). I mean, it's free-standing, but it's permanentely installed like an AC unit. As soon as the power goes off it will kick in. It's hooked right into our natural gasl line.
It turns out to be a much more expensive project than we though. While the unit, 10,000kw was roughly $6K with installation, there are also fees involved for prepping the site with a concrete pad, professional site plans prepared, pre-installation inspection, permits, extending the gas line (which includes trenching), post installation inspections, etc. We also needed to upgrade something - the gas meter maybe? All those extra things have made this easily a $10K project.
Most of our neighbors went with a 15,000kw unit, but I think they plan to run their entire house. With the 10,000kw unit that will not nearly cover the whole house (appx 6000sq ft). We have it set up to run a fridge in the garage, a stand alone freezer in the garage, the well pump (we have no water when the power goes out) then the entire basement level. It will also run the heat on the basement & 1st floor levels. We can move into the basement next time the power goes out. We didn't need anything hooked up in the kitchen as we have a gas range, which works without power.