Results of the European FP7 Sophia project roundrobin
of c-Si module power measurements at STC and
low irradiance and temperature coefficients were used to
calculate annual energy yield at four sites. The deviation
in the estimates solely due to the different measurement
results is reported, neglecting the uncertainty in the
meteorological data and losses unrelated to the
performed measurements. While minimising the
deviation in Pmax measurements remains the key
challenge, the low irradiance and temperature
coefficient contributions are shown to be significant.
Propagating the measurement deviation in c-Si module
measurements would suggest that expanded uncertainty
in energy yield due to module characterization alone can
be as high as ±3-4%