Today I received an email from LA Solar Group saying my app was certain to be approved but Tesla was sending most Powerwalls to Puerto Rico and the earliest install would be 2018.
LA Solar Group also installed my solar panels earlier this year, I was happy with their service, and signed a contract back in April to incorporate a single Powerwall into my system. The contract price was high, but I was in line for SGIP Step 1 (the largest possible SGIP rebate). Initially, I was told that they hoped to install the Powerwall in June. At my request, the contract also specified that there would be no "critical loads" subpanel, as my intention has been to back up all circuits in our home.
Tesla, however, seems to have been prioritizing Powerwall deliveries to their own customers as opposed to third party installers. Realizing this, I placed a new Powerwall reservation directly with Tesla in late August, figuring it would be best to start lining up an alternative in case LA Solar Group proved unable to acquire Powerwalls in a timely manner.
By October, LA Solar Group had a system design for me to review, and it became clear that they would not be backing up our larger circuits. This is because Tesla guidelines are generally for at least two Powerwalls to be installed if "whole home backup" is desired; Tesla doesn't want a single Powerwall system to back up any circuits above 30 amps. This appears to be a de facto requirement, not just a suggestion or mere recommendation.
Not wanting to install a "crippled" system that wouldn't cover all circuits inside the house, I cancelled the contract with LA Solar Group. Almost simultaneously, following work by their design team, Tesla got back to me with a firm, reasonable bid to install two Powerwalls for whole-home backup and TOU load shifting. LA Solar Group offered to install two Powerwalls for me, but for significantly more money than Tesla was charging, and a new SGIP application would be needed.
In spite of some uncertainty about SGIP, I went ahead and confirmed the order with Tesla, figuring that I'll most likely wind up in SGIP Step 3 or 4. Self-applying for Step 2 is an alternative that some here are pursuing, though I'm not sure whether it's worth the effort.
I've been told by Tesla that my permit application has been submitted to the county (I'm not in a city) and that the wait for installation will probably be weeks and not months. I do hope they can install before we get real winter weather here in the mountains, which always seems to lead to some power outages.
I did my solar panels this year so I need to complete the battery installation this year in order to qualify for the federal tax credit. I don't know if I believe them.
I was concerned about this also. However, based on what we now know, if you're going to be using your solar panels to charge the battery system 100% of the time, then it appears that you'll qualify for the federal ITC even if the battery system is installed in a different tax year.