Is Tesla taking advantage of me?

[Casey]

I've received a solar panel system from Tesla. they put a 11.2kw system with a 7.6 kw inverter.
I've asked them to stack it with the 3.6 inverter.
They said it's not a good idea because the 28 panels are divided into 4 group each group of 4 on their own electric string.. 3 groups of 8 panels are stringed to the inverter and 1 group of 4 panels also stringed to the inverter.
They have it all on one inverter and will not divide the panels up amongst 2 inverters a 7.6kw inverter and a 3.6kw inverter. The system is already on the house. So if they take one string of 8 panels and run it through the 3.8 inverter. It would have an undersized 3.2 kw array of 8 panels on one string running to an 3.8 kw inverter and a slightly oversized 3 strings of an 8.0 kw array of panels, 2 strings of 8 panels and 1 string of 4 panels going to the 7.6 kw inverter. They are telling me this is a bad idea and that if I want it done I will have to pay for the inverter and install.
And I am telling them that having my whole array of panels that face south east but slightly more south will be clipped too often with 7.6 kw inverter.
I kind of have them in a bind because even though they've already installed the 28 panels on 4 separate string and will turn on with a flip of the switch it is just pending inspection. However, Tesla can not bill me or request Inspection yet as they are waiting permission from me to come back with a part they didn't have with them during install, the Nero that helps with metering and the phone app. In spite of that hold up the system is functional and turns on.
They are offering a few alternative solutions.
A: I can pay for the 3.6 kw inverter out of pocket. Out of pocket because there technical team say I don't need it
B: I can pay for more panels until it meets their standard for another inverter to be stacked with the first.(The wife doesn't want any panels on the front of the house and the back is maxed out)
C: They can draw up an agreement in which I will be guaranteed that there will not be an "unhealthy" amount of clipping of the energy produced by the inverter and if there was they would need to rectify it. I guess by adding an inverter. To which I told them how are we going to agree on what's a "healthy" amount of clipping?
Can I please get advice on what I should do?

I wish Tesla had like 9 kw inverter to install but they don't and I I've received a solar panel system from Tesla.

I think the 7.6 kw inverter will be clipping the 11.2kw on too many days. I would have paid for a less panels if I knew ahead but they don't talk about the size of the inverter in the agreement we sign only that there will be an inverter.
Tesla is telling me to worry about it because I'm getting 202 percent of the energy that I need. But I say that's irrelevant because they are willing to sell me all the the panels I'm willing to buy yet want to not put in an inverter that supports that amount because they have this huge range that their two inverters cover but don't disclose this at all when signing the agreement. they don't make it clear in the contract what kind of inverter will be going with the system.
Even though l, They say I am going to get 202 percent of my energy needs but that I and my wife plan on getting electric vehicles in the future. And that was based off of 3 months of bills in the winter of a house I just moved into that runs off of natural gas in the winter and electricity for a.c.in the summer.

[Ampster]

Has Tesla given you a production estimate? I do not think they are taking advantage of you. They seem to like DC to AC ratios that approach 1.5 to 1. Yours is 1.47 to 1. Posts on other forums suggest that other installs are at that ratio and that is why I do not thing they are taking advantage of you. That is their normal system. It is too late to challenge that. Do you have a way to prove how much the clipping will reduce your production? I had a system with a 1.5 to 1 ratio installed by a different installer but production matched or exceeded their estimate and the estimate I ran on PV Watts. Yes, I saw clipping but I also saw my production ramp earlier in the day and last longer in the afternoon. I also had better production in winter because panels rarely produce at their peak.

[RichardCullip]

Have you run the two scenarios thru PVWatts? One with your 11.2kW system and DC to AC ratio of 1.47 (7.6kW inverter) and the other with a DC to AC ratio of 0.98 (7.6kW + 3.8kW inverters). You can compare the two estimates to see what clipping you might incur. If you have minimal spreadsheet skills you can even download the hourly data and see how much clipping you will will have on an hourly basis.

For grins, I did that for my location in Poway, CA and got a 3% difference btwn the yearly estimates for the two systems. Only you can tell what difference you might have and if the difference is worth fighting Tesla over..

[oregon_phil]

Casey , the 7.6kW Tesla inverter has allowable DC to AC ration of 1.7 per their datasheet. As others have said, running PV watts would be a good idea because you know more about where you live, roof slope, panel orientation, and shading than we do.

I do know that you have a new system with new panels which means zero soiling and zero degradation due to aging. On my system, I saw more clipping in year 1 because of the factors I just mentioned; less clipping in the following years. In other words, year 1 is when I watched my new system like a hawk and was most concerned about clipping.

There are also some whitepapers on the benefits of high DC to AC oversizing.

My POCO wouldn't allow me to install a system sized at 200% of usage. I think my limit was 110% based on current usage. Future usage, like Electric Cars, couldn't be used for system sizing. At some point, you become an energy provider not a residential user.

You didn't mention the size of your electrical panel or how two inverters would be wired.

In my county, I had to submit all the structural and electrical schematics to Building Permits. And I had to submit the name and model number for every piece of electrical hardware used in my system to the POCO. That way POCO could see if their equipment still works with my new solar system. After I got the original OK from County AHJ and POCO, if I changed anything, I would have to go back to them with modified drawings/schematics. which may or may not start a new round of reviews. I'm not sure what your situation is, but it is something to think about.

[Ampster]

You didn't mention the size of your electrical panel or how two inverters would be wired.

........

That is an important issue. If another 20 Amp source of generation would mean a new service panel that cost plus the inverter cost would have to be weighed against the value of any incremental kWhs generated from the larger AC capacity.

[OCJ]

I commented in your other thread. As someone also said, run it through PVWatts and quantify what you're losing yearly.

Second, what is Tesla charging you? There are reasons Tesla charges less than others, some times they make trade-offs to reduce the cost of the system. I came in at exactly $2.5 per watt, pre-sales tax and pre-incentive. We would need details of your quote to know if they are taking advantage of you, i.e. charging you $3.5 per watt.

[Ampster]

........
I kind of have them in a bind because even though they've already installed the 28 panels on 4 separate string and will turn on with a flip of the switch it is just pending inspection. However, Tesla can not bill me or request Inspection yet as they are waiting permission from me to come back with a part they didn't have with them during install, the Nero that helps with metering and the phone app. In spite of that hold up the system is functional and turns on.
..

I am not a lawyer but I was involved in the construction industry and my sense is that you do not have them in a bind. If you do not let them install the Neurio your system will be crippled in terms of functionality and reporting.. Your permission probably only extends to permission to come on your property not to install the Neurio because their contract probably covers that they have to right to complete the install and you can not withold access unreasonably. You did not mention if you paid them and how much? I suspect you probably received a good value based on comments from some Tesla Forums that I participate in. I initially got a quote from them fifteen months ago but chose to self install and my cost was not much less expensive.

[Casey]

Thanks everyone for the helpful advice. When I get a moment I'll use the pv watt's site. As of now Tesla is drawing up a warranty for me that if the inverter does clip an "unhealthy" amount that they will remedy it at their expense. I don't know exactly how the guarantee agreement is going to look just yet and what their "unhealthy" paremeters will be but I suppose as some of you have said an A.C. to D.C. ration somewhere between e rate of 1.5-1
Ampster, When I said I have them in a bind, I don't want to be unreasonable to Tesla but their inverter options can't be "ideal" for every possible array of panels and I thought I was pushing a little out of what would be an ideal inverter size. Yet Tesla allows me to assume that they would have an inverter to match an 11.2 kw array when they are really more limited than that. Granted I still need more specifics to demonstrate that would benefit and how much I would benefit from an inverter greater than 7.6kw size, like you guys mentioned I need to find out the the grade of my roof, amount of sun my area and direction of panels should expect. And input it into the PV watt's. and I will. School started this week for my children and there's 8 of them. LOL Not to mention extracurricular activities and overtime at work to pay for this syste. I'm a Correction Officer.
But here's some data below to click on. Pictures of the system and cost. Again, Thank you all very much. We are all paying alot for it and I want to make sure I am maxing out my array. Well not maxing or inverting at the D.c. to a.c electricity at an unreasonable rate but getting the most production out of it that I can with a well matched inverter because they were not upfront about their limitation of inverter size that would have helped choose a different array size that I chose.

https://photos.app.goo.gl/XBNUUA5VB7JQFg35A

[OCJ]

So you got fantastic pricing ($2.10 per watt), probably due to the simple and clean layout. I can say that in my opinion nobody is taking advantage of you.

I went ahead and bit the bullet and ran your system through PVWatts facing directly South and got a .5% annual loss from clipping. 76 kWh per year from what I ran.

Dude.

[Casey]

OCJ, That was very kind of you. And Thank you very much.

[OCJ]

You're welcome. Rest easy, you got a great deal.