> Which is why its not common, but with battery prices coming down and dirt cheap second hand batteries on the horizon, this is going to become a big industry.

Maybe briefly, especially where retail customers with some installed renewable generating capacity can leverage the latter to take advantage of net metering laws designed to bring renewable capacity to the grid, because otherwise their stuck buying at retail and, if allowed to sell back at all, selling at wholesale.

Bur cheaper batteries mean proper utility players (e.g., a joint operation of PG&E and Tesla) are building large, purpose-built storage facilities, often colocated with generation facilities, with lower marginal costs for real estate and interconnection than separate facilities and better access to financing than small operators.

Storage is going to be a big industry going forward, but the period where home storage (or storage by anyone but major utility players) is a viable financial hack rather than just a backup plan for grid failure will probably be brief unless artificially subsidized to encourage distributed storage.