Results of our 24 December 2013 Production:

The 24 th of December was a great day.  We are still trying to get some of the bugs out of our installation. One of these bugs is two tree trucks located some 35 feet from the house.  Most branches have be removed and I didn't think the tree trucks would cause any issues.  They DO!!  It was apparent from viewing the panel output because of shading, ever so faint on the panels.  It helps to stress why having SolarEdge Optimizers are SO important.  We also have 3 panels located on the south facing roof that get some shading issues as this time of year.  It goes away after noon.  The main problem is caused by a ridiculously low sun angle in the sky.

Note:  One reader gave feedback on the optimum roof angle.  I have added his feedback to the main column.  He also stated that you would only get two hours of sun in the Winter and that the south would not work because the sun is from the east. Go outside and look.  The sun is from the South of East and appears to be about 45 Degrees lower than I would like it to be.  That makes it great for the South Facing Panels and not so great for the East and West facing panels. The above graph show that you can produce power  for about 7 hours at the worst time of the year provided you have a bright sunny day.  This day was not perfect with some clouds reducing output.  We produced just under 40 kW or $15.76.  It should have been 10% higher but shading issues reduced the harvesting.  You want your histogram to be a high and wide as possible.  I believe that the East and West array did help here.  I had to drop the West panels down earlier than desired due to wind.  The East array was not effected by the wind.  I noticed just after noon that a local solar tracker was turned off because of the wind.  Thus we did better because our roof protected the East array (just a lucky day wind was from the NW).  The peak was NOT effected by any shading, only because one panel is not working very well and will be replaced in the near future.

Sunrise is reported to be around 8 am and sets around 5 pm.  Add one hour to these numbers due to obstructions from local houses and you get 9 am to 4 pm.  The shortest day of the year was on 21 December, just 3 days before.