They did not say anything about a soft-start device. I like the idea of having it on backup because I want to pull power from the Powerwalls during my PEAK period. Well as much as I can. My current PEAK is 2-8pm. In 2022 (if not sooner) it will be 4-9pm. Hoping that daily my Power Walls will charge to 100% from Solar and then I would use them thru the PEAK period. I can use credits as well but was thinking i would draw from PW. But it was a wait and see how much I use for other things. My AC here in SOCAL is about 3-4 months.It's the LRA number that matters. The maximum for two Powerwalls would be 60A. Will they install a soft-start device on your AC? If not, it won't start with just two Powerwalls.
FWIW, Tesla put my AC on the backed up panel even though it has no chance of starting during a power outage (I have whole-house backup). I wouldn't count on things working just because Tesla says so.