Selling solar back to the grid has one major problem that, fortunately, doesn't plague windmill installations: The Duck Curve [1]. The problem is that peak energy usage now occurs after sunset . So no matter how many solar panels you stack on your home, around 6-7 PM the coal, oil, and gas power plants all have to spin up to their max capacity. Your solar panels are new less likely to _replace_ a coal power plant, al…
You need a surprisingly small battery to shift use a mere 4 hours. This is why we need market rates for power, for everyone. If I have a bunch of panels and my power is worthless at 2pm, that's fine. A small battery system will pay for itself quickly if that power is worth peak at 6pm. Or maybe I set my car to charge in the early afternoon? Maybe when I install my system, I put my panels facing West instead of south?
Does a single $4,000 power-wall do that? And if it is merely saving me the cost differential from electricity at noon and electricity at 6pm, is it going to pay itself off in less than 15 years?