Problem these days are 90% or more of the residential solar sold in the U.S. is only AC-coupled and nowadays only use micro-inverters. Meaning, when the grid goes down your solar is shut down as well. Modern inverters following standard UL1741 also will de-sync from the grid just from a signal from the PowerCo through frequency shifting to shut down your solar and require your house to go in grid-only mode (when the grid has too much solar production).

Isolated DC-coupled solar is mostly done by DIY folks with inverters like Sol-Ark that can do AC or DC-coupling and can work when the grid is shutdown. Your solar constantly charges your batteries and powers your house as a microgrid. Any excess power COULD be sold back to the grid, but to avoid the added hassle of interconnection agreements, most just store it into a larger battery bank for rainy days. The goal here is to fully zero out your monthly power bill AND be self-sustaining.