Whole house generators have lots of hidden costs. Unless you can do some of the work yourself, which the contractor won’t like (ground prep,etc), it may cost $15k and up for something big enough to handle a large house.
Then, there is the power source. If it is propane, you need a large tank.350 gallon or more. If you don’t buy it, the gas company will charge you a fee for not filling it each year. If you buy it, which I recommend, there will be an installation fee, and an inspection fee every time you get a new gas company.
There will be yearly inspections and upkeep fees on the generators. Some farmers have PTO hook ups and run their generators off their tractors. A bit noisy but efficient, I think.
For years, I used a little 8000kw generator with a self-start. When the power went out, I cut off my main. (Very important for the safety of the power repair guys). Then, started my generator and back-fed it through my 220 welding plug in the garage. It ran most of my stuff in my house. I would cut off my well and not let anyone use anything big (microwave, etc. ). It could run my well but not while the furnace was running. I would run the gen for a few hours and let people do things like charge phones and power packs. Heat the house of well. Take showers. At night, I would shut the gen down and we camped out till morning.
Had to have about 20 gallons of gas on hand to make it through a few days.
8000watts not kw. In before the detail prigs.