Adding 3rd String to Existing Solaredge System

[billboe]

I installed a 11.25DC system back in 2019 which has been working great (definitely already paid for itself). And now, after purchasing an EV and with plans to build a garage/apartment next year, I'm looking to add more panels to the existing inverter. The current system is as follows:

SolarEdge SE10000-US (10kw inverter)
30x 375w panels w/ p505 optimizers (2x strings of 15)
DC/AC oversizing - 113%

I want to add 6x 410w panels using the s500b inverters (inverter oversizing jumps to 137%). The easiest option is just to add the 6 panels as its own string (the s500b minimum length is 6 panels) but it appears I may be sacrificing some efficiency with a short string??? With a new separate 3rd 6 panel string, SE estimates that I'll produce 19.21MWH. If I rewire some of the old panels such that I have the 6 new panels and 5 of the old panels in the 3rd string, the production jumps to 19.28MWh. Not a huge difference but I was surprised to see it.

Is it the short string or perhaps uneven strings that is causing the difference?

Thanks all!

[billboe]

No opinions here? Do you need more details? Here is my original post from 2019 for this install. THANKS!!!

[Mike 134]

No opinions here? Do you need more details? Here is my original post from 2019 for this install. THANKS!!!

Don't know enough about the products to give you an educated answer. That said I am an internet expert on many topics.

[billboe]

I'm back to looking at the project and wondering if anyone has thoughts on my original question?

Another option which I don't know is even feasible is adding the 6 panels with micro-converters. Maybe I would get less clipping in this scenario??? But my micro-converter knowledge needs boosting! So say I add 2.4kw of solar panels, what size wire would I need to run to my electric panel? Is there any issue with mixing a solaredge system with a m-c system?

[J.P.M.]

O.P.:

Question: Is this a grid tied system ?

Reason for question : Many states and also many utilities have limits on what can be added to an existing grid tied system.

I'd check with your POCO and find out.

FWIW, I'm in CA and therefore limited to an increase of 1 STC kW or 10% of system size, whichever is greater. Other states/utilities may have limits.
There also may be other hoops to jump through since 2019.

[billboe]

ah! that is a good question and probably why i need to go with the adding to my existing SE inverter. it is a grid-tied system (in VT) and my understanding (from memory) is that i can change the DC system size but not the AC system size (well, maybe a few percentage points?!?).

thanks for that J.P.M.!