We're going through the planning phases of installing a pair of Tesla Powerwall units for our house.
We got this via the project contact from their engineering group.
Both Tesla Powerwalls are going on the 200A subpanel that is being fed by a 200A breaker. Without derating, you can only add 40A of generation (whether it is a battery or PV). The continuous amps of the two powerwalls is 60A, which exceeds that. By derating to 175A, you are allowed 65a of generation. So, 60A (Tesla) < 65A (max allowed).
Can someone explain to me how going from a 200A panel to a 175A panel facilitates this? Isn't "more, better"? By going from a 200A down to a 175A, is this what opens up the capacity for the extra 20A that the batteries need to provide (by providing (200A - 175A) 25A)? How does that work?
Note, we already have a 7.5Kw PV system installed (I honestly don't know if its through this panel or not, the breakers are in the other, main, panel outside).
Mind, I don't question the engineers. If it has to be done, I guess it has to be done.
I just don't understand it what is going on here, and what the longer term impacts this has.
Overall we have a 400A setup in the house. I guess it's via two panels (since this one is a 200A subpanel of the other one).
Any insight appreciated.