Used car batteries can be reused for storage, so it’s going to require a cost analysis to determine what makes most sense for storage solutions. It’s great if they can use a cheaper sodium battery but we also don’t want to just waste the second hand lithium batteries. It makes sense to use both. At least until there are better recycling options. Also with solid state batteries hopefully coming up soon, it’ll still make sense to find use for the current batteries.

Ideally, home backups should be able to use any battery. Standards for compatibility would be nice.