I had a 16 KW Generac installed in 2006. Fortunately we have not needed it much. It comes on once a week to exercise itself, then just hangs around waiting for a power outage. Once the power fails, it takes about a minute for the generator to come on and get up to speed, then take over providing the power to the house. When the electric from the power company comes back, the generator switches itself off with no interruption to the electric power.
The generator has its own propane tank. Some people want it connected to the house propane, but I chose to have a separate tank. Since the generator uses very little propane, I do have to pay rent on the tank.
I have backup UPS systems on my PCs and TVs that will last longer than it takes the generator to cycle on, so I don't loose anything important while waiting for the generator.
When I bought mine, there not been many hurricanes the past year, so there was a glut of generators on the market, consequently, the prices were right. I bought mine in Michigan but got free shipping to NC.
Ziller Electric 2475 Brown Road Orion, MI 48359
http://zillerelectric.com/
I see they have 17 KW now.
I also purchased the transfer switch and had everything installed by an electrician. My generator is large enough to run the entire house and that made for a simple installation.
If you have questions, let me know.
Bob