Ballpark costs?
I have about a 2700 sq. Ft. house, and 22 KW Generator cost about $10,000. I bought it 8 years ago and it has worked well in that time. Maintenance is required once per year. It literally is powered by a small car engine that is fueled by propane. So the incremental cost spread over a decade is not as expensive as one thinks. In our case it was a necessity, because we live far out in the country with maybe six families within a 5 sq. mile area. If anything breaks down, it is difficult to get anyone to repair quickly.