A recent comparison of measurement results between CalLab PV Modules of the Fraunhofer Institute for Solar Energy Systems ISE and the Physikalisch-Technische Bundesanstalt (PTB) reveals that the two organizations deviate by less than 0.15 percent on average from the reference value when measuring the power of photovoltaic modules. Regular comparisons between independent calibration laboratories are an important component of their quality assurance process, guaranteeing that the PV industry can trust the results. In recent years, many module manufacturers' power ratings have diverged increasingly from Fraunhofer ISE measurements, with the median divergence reaching roughly 1.4 percent in 2025.
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Sophia Bächle
Communications Photovoltaics
Fraunhofer ISE
Heidenhofstr. 2
79110 Freiburg
Phone +49 761 4588-5215