Adding extra system to existing Tesla solar panel

yellowpeter

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Hello!

My home has two buildings, and last year we signed up the Tesla Solar rental program by paying $65/month for a 3.8kw system, installed on the roof of one of the building.

I am interested to DIY by either extending the current system or adding an entirely new system on my other building. Intuitively I believe by having a completely separate system on another building seems the way to go.

Ideally I would like to cover the entire roof but I would like to start small, probably just put up a few 300w panels up, but I haven't quite understand how will the new inverter connect to the existing setup? Does it automatically synchronize with the Tesla inverter as well as the gird? How will the power flow affect the existing Tesla system and the gird? I have a friend who is electrician but not specialized in Solar and I will rely on him to perform the final hook up if everything works as it should.

Does the whole thing make sense to you?

Any help would be great appreciated!
 

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svetz

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It probably depends on your inverter, I believe Tesla uses a few different third party vendors so it'll probably vary. Do you have a Powerwall or other battery system? If not, and you want one, you might look at some of the hybrid inverters on the market now.
 

yellowpeter

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It probably depends on your inverter, I believe Tesla uses a few different third party vendors so it'll probably vary. Do you have a Powerwall or other battery system? If not, and you want one, you might look at some of the hybrid inverters on the market now.

Thanks! Do you mean I might need to have a matching inverter? It is a Solar Edge 3000 inverter I believe.

I do not think I can replace it as it is a rental unit.

Thanks!
 

svetz

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There are at least different types of inverters so it can be a little confusing:

Off-grid - These inverters produce AC on their own signal, for multiple inverters to work together they need a "parallel" feature to synchronize the signal and there's usually a limit on the number that can work together.

Grid-Tied - these inverters produce AC that is synchronized to an existing source signal. Since they synchronize they can be hooked up to other Grid-Tied inverters. They shut down when the grid is not present. They should not be connected to an off-grid inverter because unlike the grid, the home is too "small" to absorb excess current. While seemingly more convenient, this type of inverter does not provide power when the grid is down (but there are solutions such as AC coupling).

Hybrid - acts as both off-grid and grid-tied in that it can synchronize to the grid, but can also provide power when the grid is down. However, since it doesn't shutdown on the loss of power, having multiple working together again requires a parallel feature.

... Do you mean I might need to have a matching inverter? ...
You might want to read up on AC and DC Coupling. I believe the SE3k is a hybrid inverter, but have no experience with it.

Hopefully, others that have a SolarEdge 3000 can tell you what they did and what's the best way to get what you want. Good luck!
 

yellowpeter

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Sep 28, 2021
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Thanks Steve!

Grid-Tied - these inverters produce AC that is synchronized to an existing source signal. Since they synchronize they can be hooked up to other Grid-Tied inverters. They shut down when the grid is not present. They should not be connected to an off-grid inverter because unlike the grid, the home is too "small" to absorb excess current. While seemingly more convenient, this type of inverter does not provide power when the grid is down (but there are solutions such as AC coupling).

This is the one I didn't quite figure out and information online is hard to come by - when there are multiple gird tie inverters running at the same time (different model that they don't talk to each other), and when the grid is offline, how does the inverter knows the actual AC grid goes down since there are multiple AC on the line at the same time? Since there are multiple AC waves matching each other at the same time.
 
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