It obviously can be done, the question is whether it makes financial sense. It seems that, if it were cost-efficient to store electricity in LiIon batteries then the biggest buyers of them would be power companies, so maybe there's some market inefficiency that you can exploit by doing it in customers houses, but it even with that it sounds like it will have a very long ROI. I pay about £400/year for electricity (about $600). A $13K battery storage array would cost me the same as almost 22 years of electricity. Even if it reduced my electricity bills to zero, it would take 22 years for it to pay for itself. I think the overnight rate, if I switch to a tariff that has one, is about half of the normal rate, so it would actually take 44 years. Probably a bit less as electricity prices are likely to go up over the next few decades, but even with a 20 year ROI there are far better uses of my money.