I installed 5kwh grid feed on my house and professionally have installed enough systems for communications towers to know the requirements. So ya I take it with a grain of salt when people suggest they can get any significant time from a battery backup system.

Also 99 percent of the home systems are grid tie and do not have a 'whole house' battery backup. Thus I am suspicious to begin when they say they get these long battery backup times and hands their AC tired in. And to make me more suspicious, nearly all grid tie systems shut completely down if the grid fails even if your in full sunlight. This is for safety reasons. A few people might have power wall type of systems but for ten thousand your only getting a few hours out of that and only on specific circuits in your house. Something that requires a bit of complexity in your electrical panel wiring.

And before you all find the 1 percent of systems that are fully backed up with battery, and they do exist, these systems to be viable have to be so overbuilt that they can cost hundred thousand dollars.