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

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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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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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I have an order for a 12.8 system and can’t get them to go any bigger than 7.6. I was told I would have to go bigger to get another inverter.

I just confirmed the plans for a 15.6 kW system with 3 Powerwalls. They finally gave me two inverters. I was surprised that it was two 7.6 kW inverters.

Their excuse for not giving me a second inverter with a 12.8 kW system was that my main panel can't handle it and that it would need to be updated. I went back to Tesla and said that's fine, I just want the job done right. I asked Tesla for a quote on how much it would cost to have them do it and the guy was just saying how it was going to be very expensive, as if he was trying to talk me out of wanting a second inverter. They never came back with an answer on the cost of the new main panel and I refused to authorize the system design/plan until I got a clear answer.

A few weeks went by and Tesla followed up a bunch of times and I kept putting authorizing the plans off. I told them to just maximize my roof space and add as many panels as possible, which came out to a 15.6 kW system. Low and behold, they were able to give me two inverters and there never was any issue with my main panel. I'm guessing they were just giving me a run around in order to not give me that second inverter with a 12.8 kW system.

In the end, sizing up to the 15.6 kW system is only a net increase of $2,800 and having that extra bit of production definitely doesn't hurt.
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