Solar street light panels should choose which direction?

Using common solar street light the panels on the azimuth chose south commonly, can maximize the solar panels on generating unit of time.

if the solar street lamps installed places such as roof, slope, mountain, building structure and the restrictions such as shadow, should consider how to make full use of the existing terrain and the area effectively, and try to avoid around the shadow cast by building, structure, or trees. As long as the south & plusmn; 20° Inside, will not have much influence on electricity, conditions permitting, should as far as possible by southwest 20 & deg; Within, make solar electricity at some peak appears in the middle of the day a little later, the number of generating favorable degrees in winter. When laying area south solar panels is not big enough, and solar panels can be laid in the east, is the direction.