two strings different production

I have 12 panels arranged in a 4 x 3 formation. All are the same brand are the same facing and angle to sun. They are wired as two strings. Was installed December, so its all new equipment.

There is passing shade during the mornings but later on both strings are not shaded.
When there is no shading issue, string two is consistently 10 -12% lower production. Is this within normal variance expectation or should they both be pretty much identical. If not, any ideas what could be causing this.

Thanks

A check of the wiring of the strings may yield benefits. There could easily be a poor connection => higher resistance. Alternatively there could be a panel with a poor cell which is dragging the whole down. Solar cells typically don't work well if any one of the cells is not up to scratch.

Basically, I suggest talking to the panel installer.

Thank you. I'll give him a call.

I had similar thoughts, but I thought, I'd ask before bothering them.

Even though your config is 4 x 3 they will likely have connected them into 2 separate strings as GE inverters have 2 Multi Point Power Trackers (MPPT) 1 for each string of panels.

Have they connected them 6 panels + 6 Panels or 5 + 7 Panels?

Also worth explaining how Series Solar Strings Work and their limitations. Have a watch of the videos lined.

Essentially you entire Series String will only perform as well as the worst performing panel in the string (in actuality as the panels are mostly "Half Cut" meaning that each individual panel is in effect 2 panels) your entire string will only perform as well as the worst performing half panel in your string.

Just as an example if one HALF panel only outputs 5 Amps instead of 10 Amps then your entire string is reduced to 5 Amps

You have 12 x Solar Panels which I assume are wired in 2 strings of 6.

So the output would be 6 Panels @ 40 Volts per panel = 240 x 5 Amps = 1200 Watts + 6 Panels @ 40 Volts per panel = 240 x 10 Amps = 2400 Watts = Total 3.6 Kilowatts

The numbers are only to illustrate one reason why you can see "capped/reduced" PV generation on a string.

Here are some decent videos.
https://www.youtube.com/watch?v=GFjL0-r6LbY
https://www.youtube.com/watch?v=NYyhy3JTEik&t=252s
https://www.youtube.com/watch?v=9XAQ4fD1a70

Optimisers Worth It or Not?
https://www.youtube.com/watch?v=UQ9Szhl1ceQ&t=851s
https://www.youtube.com/watch?v=E9NVLB_OYSU&t=83s

dragon2905 , do modern panels not also have multiple bypass diodes so that a poorly performing panel will pass the current generated by the other panels?

In my mind that would result in ((5 x 40V) - 0.6V [diode]) x 10 A = 1994 W or thereabouts for the string with the bad panel.

Simon_C again it depends on the panel and how much you spend.

Most will have at least 2 (or 3) that's the most common setup.

These are called "Half Cut" Panels.

The diodes help reduce the impact of shading (to a degree) and most importantly prevent panels from burning out or drawing power from PV Batteries.

I recommend you watch this https://www.youtube.com/watch?v=-x_6OLdAods
or
https://www.youtube.com/watch?v=BRMLvzEgvcE
https://www.youtube.com/watch?v=AZ8VQ_zmf1M