Horizontal panels have a panel slope equal to zero. Positive panel
slope tips panels up from horizontal toward South. For southern
hemisphere, use negative latitude and negative panel slope. The
calculated result is at solar noon on the 21st day of the selected
month, assuming no clouds and no shading.
Inspect the volunteered values of Latitude, Slope, and Rated Watts.
Enter different values to suit your situation. Select a month. Then
click the "Calculate" button to display the watts per square meter
generated at noon for the selected conditions in the selected month.