Cost effective local battery storage is fully achievable in the next few years? Admittedly I know next to nothing on the battery industry, but I find that very hard to believe. Perhaps I am over estimating the capacity of such a battery, as I assume you mean one capable of storing enough electricity to power a home at least over night, realistically 48-72 hours would be required.
And don't forget they will have to also charge your electric vehicles, as that is mainly performed overnight for several reasons from what I understand.
And that many batteries of that capacity would be an environmental nightmare I assume, probably not even possible to build the manufacturing this would require due to current environmental protection laws ironically.
Again I fully admit my ignorance on this subject, if you have a pointer to a primer on what you are referring the I will happily read it. And I hope I am wrong as well, current battery technology seems to be a constant roadblock to many environmentally friendly solutions.