I really like the souns of the Generac unit but $12-$15K is a bit steep.... The house is only about 2,700 sq ft with one AC unit so I can probably get away with something a little less.

I found a Yamaha that is a tri-fuel.... Gasoline, Propane or Natural gas... seemed like an interesting way to go. It isn't a stand by unit but might be a good solution considering a lot of areas around lost gas service too. I'll have to find some reviews because I'm a interested in how the engine holds up when switching between 3 different fuel types.