We put in an "automatic standby generator" recently, natural gas powered. It is not a "whole house generator." It is 8kw.

It covers critical circuits in the house--medical equipment, fridge (insulin storage, food) freezer, and sump pump, with just enough left over for some lights (not all rooms) and tv. Our stove is gas. Installed, with transfer panel, it ran around 8500. No 220, so no AC.

The past few years we had been using a portable generator for our frequent power outages, but as medical needs for my DW grew, and my age went up, it seemed to move from "nice to have" to "gotta have."

There is something you may not be aware of that limits what you can do. This is the size of the gas line and meter serving your house. In my case, all I had to do was swap out the meter for a larger one, and have the gas company dig up my lawn to locate and remove a limiter valve in the gas line serving the house. They did this at no cost. The capacity of the gas line itself was sufficient (with the removal of the limiter valve) to serve the existing gas appliances and the new generator. The gas company had to review and approve the new generator's gas usage before it was installed to be sure there was capacity for it. The larger the generator, the more chance you will run out of capacity in your gas line service.

IF they had determined the gas line service was not adequate, it may be possible to run a new gas line from the main to your house. This is very expensive--around here, another 10K minimum in addition to the cost of the generator installation itself. The cost (in our case) could have gone over 20K total if a new gas line was required. We put a clause in the generator contractor's contract that if the gas company said we needed a new gas line, then the contract for the generator installation was cancelled at no cost to us.

Bottom line is that I am very satisfied with the generator, and we have needed it on 2 or 3 occasions since it was installed.

But I think "whole house" is probably unrealistic. Try taking a close look at what you really need. For example, do the bedrooms really need power? Do the washer and dryer? The garage door opener? All the light and sockets?

One way to check is to throw off the breakers in your box one at a time, and find out which circuits you really really need. Add up those circuits and it will put you in the ball park for the size generator you need. Note that switching what is on what circuit in the house can add to the expense. The generator transfer box installer will want to identify whole circuits in your existing box to put onto the automatic transfer box.

Hope this helps.