My understanding is that most Californian's are net consumers and those of us that are net producers are in the minority. The bucket that you are in will drive different cost/benefit decisions.
Net producers want to maximize their net exports while keeping their annual NBCs for imports below their annual MDCs. Using Powerwalls results in a 10% recharge penalty reducing net exports and should be avoided. If you are with a CCA that compensates net exports at retail rates (I think there are 1 or 2 that still do) then it may make sense to use the Powerwall during Peak to maximize the return for Solar exports and without offsetting Peak imports. Absent this case, using Powerwalls has no benefit other than the potential unverified claim that keeping your Powerwall at 100% for extended periods of time will significantly degrade the capacity. If you are not using Powerwalls daily then your baseline is 0 kWh and you would get the maximum value when it does discharge during a VPP event.
My CCA has a non-TOU compensation rate that is twice the PG&E NSC, so I am not incentivized to use my Powerwalls during Peak. I do pay heed to the possibility that keeping the Powerwalls at 100% is potentially harmful and I would like any failure to be observed outside of power outage, so I do allow them to lightly discharge during Peak.
- Winter - Reserve set to 90% and Peak set to 7:00-9:00pm (any solar goes to the house from 4:00-7:00pm)
- Summer - Reserve set to 85% and Peak set to 4:00-9:00pm (front loads discharge to 4:00-6:00pm outside of typical VPP hours)