It was cheaper for us to get a 20 kW than a 12 kW because the latter would have required a lot more labor for a special panel of critical circuits. With the 20, they just wired straight into the main board. Very happy with the propane Kohler. It's nice getting emails whenever it starts up and shuts down. I bought from electricgeneratorsdirect.com and found local electrician and a plumber for the propane hookup; no regrets.