Thought I'd give an update on this since everyone was so kind answering my questions.
I think I read this mode of operation was only allowed starting with the IRA on Jan 1st, 2023 (along with the tax credit) so maybe that's why it's hard to find other folks that use this configuration.
It's done.
View attachment 995984
I ended up cancelling the Tesla order and going with a third party installer. I'm in Spring so there was no permitting or inspections required, just the Centerpoint paperwork which got approved in hours after signing ........ well, I'm not really sure what I signed.
Date of Order: Sep 28th, PTO: Nov 16th.
I found out that I am the only customer they have that is using backup only, no solar.
I have two modes of use, Backup-Only, the reserve is set to 100% or TOU when the reserve is set lower. I am currently using a reserve of 80% which the app says allows TOU of 20%. However, my current electric plan is fixed rate so the TOU part is currently unused. In the New Year I'll be looking at changing my plan to see if I can charge for free at nights and run the batteries during the day. Not sure how it will work when my AC drains the batteries down pretty quick.
When I lowered the reserve from 100% to 80% the house ran off batteries for 11 hours while draining the 20%. I think that's pretty good, they should last almost a couple of days without AC if needed.
The batteries seem to top off maybe twice a day for about 5 mins each. That's about .7 kWh per day. I figure it costs me about $2 - $3 per month to have the security of the batteries to backup the power.
Thanks to all for the knowledge you have shared. I'll keep reading.