so there is not much point in going to the effort of tilting. the reason for this is that the days are long and the sun is high in the sky for much of the day– so, it shines on the flat panel at a good angle for many hours. for the tilted panel, the sun is actually behind the panel for several hours near sunrise and sunset.
in mid winter, the tilted panel does quite a bit better than the flat panel, and the further north the location, the larger the difference between tilted and flat. this is because the sun is low in the sky and does not make 