Posted by Ron Rosenfeld on July 26, 2010, 3:25 am
On Sun, 25 Jul 2010 23:05:01 -0400, "Martin Riddle"
What system are you using for rating the panels?
What is the source of your "notes"?
Posted by Martin Riddle on July 31, 2010, 2:01 am
The PVwatts system is a good system, heres a list of derating factors.
Dust, or Soiling (as it is listed) Does vary with location.
But generally, the system efficiency is ~75%
Posted by Ron Rosenfeld on July 31, 2010, 2:33 am
On Fri, 30 Jul 2010 22:01:31 -0400, "Martin Riddle"
I would agree with their derating system, but note that they start
with STC nameplate values. And there are site specific issues
including not only dust, but also snow; shading, and so forth.