3.5 sun-hours is the design number.
We size every array in Northern Indiana against 3.5 sun-hours a day. That's what your panels will actually give you across the whole year — not the peak, not the sunny day, the whole year averaged including winter.
Peak summer? 6 sun-hours is real. But that's exactly when your A/C is stealing production. So we don't count on the peak. We count on the average.
Under 3.5 happens. Three cloudy weeks. Wildfire smoke. Snow on modules for days. Panel degradation. A tree that grew. We design so those weeks don't leave you cold.