The power output of the photovoltaic solar panels is, of course, affected by their orientation and their tilt angle to the sun. This will vary depending on the time of year. A solar system can be most efficient if the tilt angle can be changed for seasonal sun movement. The best tilt angle is usually equal to your latitude.
For example, San Francisco is at latitude 38 ° and if solar panels are tilted at 38° they would be perpendicular to the sun twice a year between equinoxes.
Use the following chart to determine efficiency percentages with varying tilt angles and orientation.
A number of 1.0 on the chart is the most efficient.
Orientation Factor For Annual Energy Production in Sacramento, California
|PV Panel Tilt Angle from Horizontal|