Most Australian solar installations use string inverters where solar panels are connected in series with an electrical cable. Each group of panels in series is called a string. Each string is connected into a separate input on the inverter.
In the configuration above, each string can have a different numbers of panels and each string can face different directions. You could even have a different type of panel for each string. This is because each inverter input is connected to a separate Maximum Power Point Tracker (MPPT). The MPPTs optimise each input separately.
Sometimes multiple strings are connected in parallel, into one inverter input. To do this each string must have the same number of panels and they must be identical brands and models.
Generally speaking all the panels in the configuration above need to be facing the same direction, or the MPPT struggles to optimise the array efficiently.
If an east/west split of solar panels is desired, where some panels are facing east and some facing west, then normally those panels would be placed on separate strings and a two-input inverter would be used.
I Didn’t Believe It Myself At First
When I was told it was possible to put both east and west-facing panels on the same inverter input without a serious decline in performance, I was very sceptical. I was all, “Nah! That’ll never work!
When the sun isn’t directly overhead the two sets of panels will receive different amounts of light and, since they’re on the same input, the mismatch will cripple the MPPT’s optimisation and pull down the performance of the others. It’s not a good combination. Putting east and west-facing panels on a single input is like putting chalk and cheese together in a sandwich and hoping the contrast of flavours will result in a taste sensation.”
But I looked it up and it turned out to actually be correct, but only under the right circumstances.
Dietmar Is The Dude With The Dirt On Single String Shenanigans
When it comes to getting the low down on east/west splitting on a single inverter input, Dietmar Staudacher is the man to turn to. Or at least I assume he is a man. Very few women are called Dietmar. But I’m sure those women who are called that are quite impressive.
Dietmar wrote, Ost/West-Ausgerichtete PV-Anlagen Mit Nur Einem MPP-Tracker, and you can read a PDF of that paper in its original German here. Fortunately, I am extremely talented at reading German… after it has been translated into English. And you can read a translated PDF by clicking on its English title, Efficient East-West Orientated PV Systems With One MPP Tracker.
Now note that Deitmar’s paper was published 7 years ago, which is like 7 years in solar years. There have been a lot of developments since then. But his basic conclusions are still sound.