Good Advice from IzzyJG.
My generator is a Generac also.
And I did forget to mention that what you have wired into the transfer panel has to pass county electrical inspection for the size generator you are installing. Actually, you need both gas and electrical inspections.
I think it is a "devil is in the details" problem-- what is on which circuit, how many circuits = what KW need = what size generator, and then what can be done at what cost.
Hard to get your head around, but the key is "survival" and not "everything is just like normal."
Top priority in our case was DW's needs. All else secondary. The installers told me about 80% of the systems they install are for medical reasons.
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"Better is the enemy of good enough."