Thanks for your reply August. I'm quite surprised that you have two Uni-Solar systems not performing well. Third party testing consistently proved them the top performer. (eg. Santa Cruz and Tucson sites) With my experience both on and off grid, I am convinced. Panasonic was great because, in addition to performance, it also had very high efficiency. In my world of cramming 2kW+ PV arrays on the roof of an RV or boat, that is also a necessity. Example: Here's todays job; the last of my Panasonic stock, 1410 Watts on a 40' coach. No possible way to do this with standard 60 cell modules. Bottom line for me is, someone has a best and worst performing PV module just like someone has the most efficient. Glad to hear your SunPower installs are producing above expectations. That's probably what I will go with. Larry On Mar 14, 2014, at 9:50 AM, August Goers <[email protected]> wrote: Hi Larry, It sounds like you are talking about the temperature coefficient or energy yield per kW-peak? Uni-Solar was great on paper but I'm not so sure about real world performance. We have a couple of Uni-Solar systems installed a while back and they are not doing so well in the real world. Companies keep coming to me over the years claiming that their modules harvest more kWh per kW peak and it is really hard to keep everything straight. Certainly the PTC ratings help in comparison to STC. Then there are papers like this from SunPower claiming 8 to 10% more energy per Watt: http://www.solarips.com/admin/content/uploads/SunPower_Yield_Report_BEW.pd f SunPower also claims that their modules degrade less annually compared to others. And here's a doc comparing PV module performance measurements: http://fire.nist.gov/bfrlpubs/build05/PDF/b05047.pdf Each year we try to compare the actual monitored performance of our systems compared to our as-built production estimates at time of the installation completion. In general, I've found that both SunPower and other standard efficiency modules seem to outperform the normal PV-Watts calculation by 7 to 10%. In 2012 our systems were averaging about 17% above our estimates! I haven't seen a huge difference between SunPower and standard efficiency modules. Furthermore, I haven't seen the performance gains that microinverter manufacturers are claiming compared to string inverters. I admit that our informal comparison is not perfectly scientific because there are simply too many variables that we don't capture. My main concern is material and or workmanship degradation in modules over the long haul. Only time will tell. Best, August |
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