[hagbard_c]

The "correct" tilt in the more northern and southern regions as well in higher places is "enough so the snow slides off the panels". I built a barn with a roof at the "correct" 36° angle specifically so that the panels - 36x400W - both produce the maximum amount during the summer months as well as shed snow without the need for manual intervention.

[gonesilent]

So that's about a 8/12 roof pitch ish.

[hagbard_c]

8.7/12 to be somewhat more exact, i.e. ~9/12 or 73%.