I don't think there's any particular economy of scale to renewables beyond amortising installation costs.

This is a really big component in most western countries, so big installations are always going to be more cost effective, but there's nothing special about storage vs solar or anything else.

I suppose storage is smaller, so you don't have to pay for much land like you would solar (and where homeowners are basically utilising an underused resource so they have a cost advantage in that respect)