I know you're all hyped up about your home lithium battery power system, but there's a much simpler way to store solar energy, called thermal mass storage. When the sun is shining during the day, store excess thermal energy to use at night and on cloudy, overcast days.
Basically it's a bunch of rocks, in an insulated box. Bricks with holes in them work pretty well too. A nice big 1 meter by 1 meter by 2 meter tall stack of bricks would store quite a bit of thermal energy. Customers who want more thermal storage capacity just need a bigger box with more bricks stacked in it.
You guys love exotic materials so insulate the box with aerogel, and then you can chill the bricks to -50C or heat them to +200C using spare solar energy, and they will hold that thermal charge for days with minimal loss.
Then all people need to do is blow air through the bricks with a fan when the sun isn't shining and hey, free air conditioning or heating. (Use an air-to-air heat exchanger to keep the bricks free of dust and moisture.)
This would be great for solar panel users whose electric utility doesn't reimburse for or pays very little for surplus generation.