PV power tolerance [RE-wrenches]

[Marco Mangelsdorf]

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My understanding of the term "power tolerance" as it relates to module
output: when a PV manufacturer claims that their nominal 100-watt module has
a power tolerance of +/- 5 percent, this means that the module is guaranteed
to have put out a minimum 95 watts under STC (it's relatively rare that
we're going to see a 100-watt module put out 105 watts STC); if it did they
would call it a 105-watt module and charge us accordingly.

Looking at different manufacturers yields different power tolerance ranges:
BP Solar, for their larger output modules, claims a 5 percent PT and even a
0 percent PT for their not-available-in-the-U.S. 7180 180-watt module; Shell
has 5 percent; RWESS, for their ASE300s, has a practical 0 percent PT as
well; Sharp has a 10 percent PT (now, who would want to go with a Sharp
array with that kind of PT when one can likely get more real power from a
BPS, Shell or RWESS array?), etc.

My interest: what kind of performance (real world kW DC and AC kWhs) are you
all getting from your various PV installations?  Are you generally satisfied
with your PV manufacturers' output claims?  Have many of you had
low-performing systems which are due to disappointing array output due to
under-performing modules?  

Unfortunately, with the sky-high global demand for modules these days, the
manufacturers can sell virtually everything that rolls out of their assembly
lines and not necessarily be all that concerned about power tolerance
issues.  Not only that, but prices have gone up this year with more price
increases to come.  Still, I think that it's important to get some more real
world empirical data on performance; simply using the CEC derate number per
module doesn't cut it for me.


Marco Mangelsdorf
President
ProVision Technologies, Inc.
69 Railroad Avenue, A-7
Hilo, Hawai'i 96720
(808) 969-3281, 934-7462 facsimile
www.provisiontechnologies.com

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