I guess this is also true for Hackernews repl

I mean you couldn't sell is warranted as a 20kWh pack. That much is true. But for most home stationary storage purposes I'm not sure how important the exact capacity is, things like shifting power use onto the low side of a dual rate tariff and maximizing the potential of roof top solar.

It depends on the use case. For time-shifting loads and playing power arbitrage, maybe not much. But in some cases having a few days of autonomy can be nice during a storm or ~freak~/"new normal" weather events. If you live in the US West, wildfires are increasingly common (and we're just getting started) and much of California is expected to have to learn to deal with rolling brownouts and blackouts for the next few years during the warm season while PG&E is upgrading and burying their sparkly infrastructure. And if you live in Texas, I guess you're just signed up to pay infinite dollars for power whenever the market demands it.

In a functional grid, each home shouldn't need its own battery system. But we've neglected ours for so long, both technically and politically, that there's no real hope in improving it in the short term, so homeowners can either take it into their own hands or just go without electricity a week or two out of the year.