If you watch YouTube 'fully charged'
He had a powerwall installed. Tidy installation. Two things put me off,
first when there is a power outage, the switch over to the power wall is not seamless, upto several seconds downtime. This on/off can damage house electronic equipment.
secondly. You cant power the heating from the powerwall it limited to a several kW demand
Cannot comment on grid back up, but the PW can deliver 5KW continuous with no issues. That's alot of power. You can also stack them, so 2 PWs will provide 10KW, I cannot think of many dosmetic usage that requires that amount of power constantly.