Here is the link to the graphical calculator: You put in your latitude and 'angle of panel tilt', and you get a graph of effective radiation to the panel through the year (in "standard", cloud-free sea level conditions):
http://www.pveducation.org/pvcdrom/p...surfacehttp://
Don't use the first calculator, or the really complex one inside the yellow box- go down the page, to the graph, and enter your values underneath. If your panels are horizontal, like mine, then you need enter only latitude - the graph always shows results for "flat" panels as a red line. (If you have one panel mounted across the centerline of a roof shell, or two panels equidistant from that centerline, then your average 'angle of inclination' is zero.)
Solar output for a particular panel orientation varies, according to two factors:
1) How far North (latitude) your Campground is located; and
2) What day of the year you are camping.
Winter days are bad for for "horizontal" panels. First, the sun is low on the horizon; and second, the days are short. Summer days are better than you might think, because the days are so much longer AND the angle of incidence is more favorable.
For Reno NV, on the best day of summer, the total daily energy into "horizontal" panels is only about 10% less than the energy into perfectly aligned panels (they would be titled about 25 degrees above horizontal). But for the worst days of Winter, a perfectly aligned panel (at about 49 degrees) would get only get about 40% of the summertime max, and my "flat" arrangement will create only 18% of summertime maximum power per day.
Power Calculator for Seasonal Effects and Angle of Panel Mounting
Linear Mode
