We have the 10kW Generac and panel to back up a 2000 sf house. It is 2 years now, and has been a great addition. Heat, water, and range are propane, so the generator is too... I would have preferred diesel for cost reasons, but the tank is here so it made sense.
It runs the weekly test cycle for 20 minutes and fires right up. While it is not whisper quiet, it is quiet for a generator. It will run most of the house and the a/c, which is the critical thing here.
I paid an electrician to connect it (he brought a sub to do the propane hook up), and he was way out of his depth... if you are hiring, find someone who has done these before. This poor guy had to have lost money on the job and I had a lot of cleanup on my hands.
Now I need a portable of some kind to back up the well pump, which is on a separate service.