Comment by bruce511

I can speak to this somewhat. My panels are on adjustable frames. Typically I switch from flat (summer) to tilted (winter).

As always ymmv and depends somewhat on your location. I'm around 30 degrees from the equator.

During summer, lying flat gets a lot more power. And more importantly the start and end of the generating period is longer. Ie the panels get more sun in the morning and evening thankfully they were tilted.

In winter the sun is more "from one direction" and obviously is lower on the horizon.