As with any other “techie” setup, the rabbit holes to pursue are endless. I don’t see backup as a rabbit hole. I see backup as the only real way to get off of the grid. Backup systems, such as Tesla Powerwalls, qualify for the Federal Solar Tax credit. So there’s that too.
If you install only solar panels and you feed the grid your excess power during the day, then draw it back at night, that is a good way to offset your power costs. What this setup fails to provide is power during a grid outage. Your panels will not power your home in the case of a power outage unless you have a backup setup in place. This is because while your panels are powering your home, they can also send power to the grid. In cases of a grid outage, all reverse power feeds must be shut off to keep from electrocuting workers who might be working on the grid during its outage. This will be the same everywhere.
If you have, say, a battery backup system, when the grid goes out your home will draw from the panels first, then from your backup. Your panels will first power your home, then recharge the batteries while pushing no power to the grid.
If your backup system is strong enough to run your entire household, you will not even notice grid outages as long as your batteries are charged and/or your panels are producing enough power for your home.
So really, while backup power is an option for a solar system, if grid independence is your goal, add it to your list of needs.