Originally Posted by mnoland30
Sloping your panel at 45į will help the snow melt off, and help clean it when it rains. Solar panels are more effeicient in the cold, so pointing east might work best, but in snow country, I'd aim it southwest so that the sun melts the snow during the warmest part of the day. <clip>
For the real facts on solar panel orientation, here's a calculator
You can see the difference between panels laid flat vs at the proper angle for sun in your location. Also, what direction to face the panel (South, generally). You'd want to orient the panel for the "winter" sun path (more vertical) rather than the "summer" sun path (higher overhead) to obtain more Photovoltaic Energy during the winter. For a full year of a single angle, they suggest using your latitude (mine's about 46 degrees) for the angle.
Also, living in snow country, consider placing the panels at an angle so that the snow might sluff off when it falls rather than piling up on a flat panel surface.
Note also that it will base its calculations on your specific location. For instance, I live at 46 degrees N latitude in the Northern Rockies. If I change the location to a similar location at the same latitude in the Pacific Northwest where it is usually cloudy during the winter, my solar panel output drops by about 30%.