It makes sense only if the house also have solar panels (that don't need grid cost for in-house use). Without solar panels (or other generators), regardless of where battery locates, they need to pay grid cost someday. Though there are other benefits: backup for interruption, utilize parked vehicle by V2X
It reduces peak amperage requirements which has a big impact since cable heating is proportional to the square of the current.
Ah reduce peak grid usage is reasonable, though it's not applied to how grid cost charged for house here now.