Los Angeles
Optimum Tilt of Solar Panels by Month
Figures shown in degrees from vertical

Jan Feb Mar Apr May Jun
40° 48° 56° 64° 72° 80°
 
Jul Aug	Sep Oct	Nov Dec
72° 64° 56° 48° 40° 32°
 

Winter
  32° angle	 	

Spring/Fall
  56° angle	 	

Summer
  80° angle
Notes:
On the 21st December, the sun will rise 74° east of due south and set 74° west of due south.

On the 21st March/21st September, the sun will rise 91° east of due south and set 91° west of due south.

On the 21st June, the sun will rise 108° east of due south and set 108° west of due south.


source: http://www.gogreensolar.com/pages/solar-panel-tilt-calculator