Guess I’ll have to contact Tesla then. And find some threads on what to set reserve % at once PV is on. Thx.
What percentage to set it at is a pretty personal decision, there is no "correct" answer for this. For my own personal use case, that percentage depends on a few different things, so I change it manually fairly often in fact.
In general, the "reserve percentage" is "the percentage of total powerwall energy I want to leave in my powerwalls, so that they have power in case of a power outage".
A little more specifically, its the amount of power you think you will need in the powerwalls to last you until the sun comes back up again and starts charging your powerwalls again, in case of a power outage. You can put as much or as little thought into it as you want. In my specific case, when I got my powerwalls installed in January, I had the reserve percentage set higher than I do right now (because my PV system makes less power in january than it does now, as do most peoples).
Right now, on a sunny day, my PV system can fill my (2) powerwalls from 25% to 100% by about 12noon to 12:30pm, even with the PV covering the house draw as well. I have my reserve set to 25 percent, because, I just need enough power in the batteries overnight to ensure that, if the power went out while I was sleep (minimal draw anyway during that time for me), the powerwalls would power the house till the sun came up.
That number is going to be different for different people with different electricity usage profiles, and also whether they are on a time of use plan (and thus trying to cover peak usage during a regular day) or not. Since I am not on time of use, but a regular old school tiered rate plan where the more you use the more they charge you, WHEN I use my power doesnt matter. Its no cheaper for me to use power in the middle of the night than it is during the day on my plan. I get charged more for how much total I consume, so I am incentivised to reduce my usage as much as possible, in total.
I also change my reserve percentage manually, if (for example) I know there is going to be rain / overcast the next day, so I am going to generate less PV power. I bump it up manually to a higher reserve number, because if its overcast / raining, I generate less PV energy, so "if" the power went out, the powerwalls would have to cover me longer. My goal is to NEVER AGAIN EVER deal with having "no power" while I am living in this house again (ever). I dont mind micromanaging the reserve to ensure I am doing what I can to minimize that chance.
I have 2 powerwalls and wish I had bought 3, because for most of the year I would have no issues generating enough PV to "fill" 3, and it would enable me to charge my car a bit more easily for my normal commute.
Anyway, I dont use the cost savings or advanced modes, so not sure how people set their reserves for those, but the same general thought process applies, which is "how much do I need to ensure is in the battery so that it can power my "stuff" if the power goes out, till the next sunny day".
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TL ; DR ?
Powerwall reserve settings are something each person needs to decide on for themselves, based on their expectations and system performance. There isnt a correct way to set it, only a correct way for "you".