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SPA signed for a 12.8kW system with 3 Powerwalls - Have some questions.

I just signed the Tesla SPA last week for a 12.8kW system with 3 Powerwalls for whole home backup. I had some general questions, what I should be aware of during the site assessment, and what important questions to ask the technician during the site assessment. Any help or guidance would be greatly appreciated.

I'm in Orange County, California. There will be 13 panels (5.2 kW) facing North and 19 panels (7.6 kW) South, with no obstruction. Tesla is estimating the panels to produce 18,393 kWh/yr.

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- I was looking over the SPA and there's a line item for "Inverter(s) & Balance of System" which costs $4,820.
  • Based on the cost, is this the cost of 2 inverters, one 7.6 kW and one 3.8 kW inverter?
  • If there are two inverters, my Inverter Load Ratio (ILR) will be 1.12, which is an acceptable ratio?
I read on another thread that Tesla installed only one 7.6 kW inverter with a 12.6 kW system and the owner is experiencing a lot of clipping. I hope that's an oversight by Tesla and not something they're doing on a regular basis. The thread can be found here.

- For the "3 x Powerwalls" line item, there's a bit in parenthesis underneath that says "Includes integrated or separate System communication device".
  • What does "Includes integrated or separate System communication device" mean? Is one better than the other (integrated vs separate)?
  • Also, I assume I'll be getting 3 new Powerwall 2+ by default or do I have to specifically ask for the 2+ over the normal 2?

- My house was built in the early 2000s and I'm not sure if my Main Panel needs to be upgraded (Main Panel Image Attached Below). I plan on installing the JuiceBox 48 EV charging station in the garage as well, so wanted to make sure I can supply it with the required 60A.
  • Will the Main Panel be able to handle the new solar system with whole house backup by the 3 Powerwall 2+ and the installation of the above EV charging station?
  • I plan on installing the 3 Powerwalls in the garage, will the Main Panel need to be moved from outside and in to the garage? (The Main Panel shares the same wall with where I want the Powerwalls installed.)

- Site Assessment
  • Anything important I should look out for or ask during the visit by the technician?

If there's any other information I can provide, please let me know. Thanks in advance for everyones' time and help, I really appreciate it!


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OD 7/27 MYLR Red/Black 19's/ No FSD/ Del 11/20
Supporting Member
Dec 14, 2013
Thank you for posting the cost breakdown. I have been thinking about buying a system of about the same size, so your data is useful for a ballpark figure at least.

You might run your system configuration in PVWatts just to see if the output numbers are close. As I understand it you should do 3 calculations. One for each group of panels.
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