Make sure you (or electrician) evaluate your main panel, as it will become a sub-panel with the install of the ATS and whatever you may need to add to bring it all up to code (disconnects, etc.). As a sub-panel it will have to have the neutrals separated from the grounds with separate bus bars. I have an older split bus 150 amp main that is FULL. It was going to cost me $8-$10k just to upgrade/prepare my house for installation of an ATS before I even got started on the generator install. Ruined my plans altogether.