Funny question. I have heard of PG&E limiting installs to 110% of consumption (but don't actually enforce it). Is it possible Tesla is low-balling the estimate to please the utility?
I would think they would get in trouble if they were systematically trying to do that.
I have SCE and my production needs is better aligned to the 8kW system, but I decided to oversize it to give me some extra room for growth (more AC usage, electric car, etc.). Tesla made me sign a form for SCE acknowledging my system production is higher than my current usage but I expect my usage will increase. I assume they do something similar for PG&E. Here is the wording from the document:
"I have compared the estimated annual production of my Generating Facility with my most recent 12-month usage history. I am aware that my Generating Facility is expected to produce more energy than I used in the last 12 months. However, I affirm that I expect to increase my usage accordingly in the upcoming year. My Generating Facility was sized to meet this expected increase;"