We have 4 120W panels mounted on the bimini - two on each side. They are wired with 4AWG wire, so voltage drop is minimal. We are in the Southern Caribbean, so sunlight hours are constant year round.

Two years ago we got an MPPT controller to replace our old PWM controller - this let me experiment with series vs. parallel configurations. Daily data from a month in each configuration were recorded and compared.

The bottom line is that wiring the system to have two panels on the same side in series, with the two series in parallel gave us a 25% increase in daily AH. Wiring them all in series suffered from shading issues.

I contribute this gain to taking better advantage of the early and late day lower light levels. The average current output during high sun did not change.

However, you can fry an egg on the panels down here, and the panel output is attenuated accordingly. In cooler climes, I suspect that the average current output during high sun would also be larger and the daily gains more.

Also, mornings and nights down here happen like a light switch was thrown. In Northern latts where twilight occurs more slowly, series configurations would take even more advantage of those conditions.

Mark