Storing energy in batteries is a net loss. Even at retail prices, the total electricity stored in the battery over its entire lifespan will not pay for the upfront cost of the battery. Even if the electricity were free.
Batteries are a generic technology. If they were useful for grid energy storage, they would be used for it already, not just useful for exotic future energy generation methods. In particular, wind power is terrible because it is erratic (and badly timed where it has trends) and would be the existing technology to most benefit from improved storage.
That hasn't stooped Musk planning to couple batteries with solar power.
This thread is for asking any questions that might seem obvious, tangential, silly or what-have-you. Don't be shy, everyone has holes in their knowledge, though the fewer and the smaller we can make them, the better.
Please be respectful of other people's admitting ignorance and don't mock them for it, as they're doing a noble thing.
To any future monthly posters of SQ threads, please remember to add the "stupid_questions" tag.