I don't have solar panels, but an auto-standby generator. That generator has it's own electrical panel, which is connected to the main panel. When the main power goes out, a switch is tripped, and the generator panel is fully disconnected from the main panel,so no power going back out, but those circuits in the house from the generator panel have power.

So, it appears that there is no such system with solar panels?

What would it take to install one? Perhaps a separate panel and a battery system to smooth out the varying input from the solar panels?