alt Hacker NewsI think you're looking for the term "islanding".
It's becoming more and more common for PV systems with a battery system to be able to work in an islanded mode, and more importantly - they're legal and code compliant to do so.
When the grid goes down/out of spec, they disconnect the home from the grid and continue to power locally.
Examples of this include Tesla and Sigenergy.
Some are able to do this in very short periods and able to operate effectively as a whole-house UPS. Some will have a flickr of the lights and maybe some sensitive devices will restart. Others will take some period of time to disconnect from the grid and run in islanded mode.
For general interest, Western Australia's State Power company has a variety of battery application cases that it assists with; home batteries, community batteries, fully stand alone, microgrids (with batteries).
https://www.westernpower.com.au/resources-education/consumer...
https://www.wa.gov.au/organisation/energy-policy-wa/wa-resid...
West and South Australia are a fair way down the integrated renewables pathway with a high percentage of household rooftop solar, mixed rural PV farms, wind power, battery farms, etc.