In December of 2008, after 13 months online, we had our first zero power production day. On December 20th, our solar panels were completely covered with snow. On that day and the next 6 our panels were covered and produced no power. In the three pictures below, you can see the progression of snow.
Full Power Production
Minimal Power Production
On the night of December 26th, after a day of rain, with a big crash, the snow and ice slid off all at once, leaving just a little snow on 2 panels.