When I did the math for our house, despite a 13yen difference between night and day, the power wall never made recoup. The biggest issue is battery's limited life cycle and overall high cost.

The math worked out to 30 years before raw recoup. Once you add in a discount rate or life cycle would never justify itself. The per watt hour cost installed keeps to come down massively.

I imagine that in a world where a substantial proportion of energy came from solar, the night-day difference would be much more pronounced, and the economics would shift.

I am currently working on something that is trying to solve this by more accurately pricing DERs https://www.greentechmedia.com/articles/read/opus-one-tests-...

Move to California, which has very high electric prices and time-of-use variations are extreme.

Solar and batteries are economical.