[msandford]

The question isn't "why would I want that" it's more "given that I live in a place where grid hookup is $100k since I'm 10 miles from the nearest power line, what is my next cheapest alternative?"

Once the question is framed properly -- at least for a few million people in the US -- then the motivation for storage becomes much clearer. If you have a battery and an inverter then you hook that up and it feeds the house. And all your other power generation choices feed the battery. Solar, wind, hydro (if you live on/near a stream or river), small generator, etc.

If it costs $100k to get hooked up and then you're paying some fee for power every month it might make sense to buy the battery for $20k, buy a generator for $5k and spend $10k on a wind turbine and $10k on solar. That's $45k versus $100k which is a good chunk of change plus you can expect your prices to go down as solar panels and batteries and whatnot get cheaper, whereas fuel is only going to get more expensive.