My utility in Arizona calls peak hours noon to 19:00, and power is about 5x more expensive during that period. By setting my backup percentage at 100% during off-peak hours and, say, 20% during on-peak, I can get the Powerwall to charge during the morning sunlight hours, and provide power to the house in the early evening after sundown. This would seem to abide by the somewhat silly requirement to not charge the Powerwall from the grid, and still allow me to derive some benefit from the batteries.
The problem is: I have to do this EVERY day, MANUALLY, and even guess at what time to make the change on the app since it seems to take a variable time for the change to be transmitted to the system.
Dear Tesla: Please make your app more functional!