Building integrated photovoltaics, the integration of photovoltaic cells into one or more exterior building surfaces, represents a small but growing part of today's $2 billion dollar. photovoltaic industry. A barrier to the widespread use of building integrated photovoltaics (BIPV) is the lack of validated predictive simulation tools needed to make informed economic decisions. The National Institute of Standards and Technology (NIST) has undertaken a multi-year project to compare the measured performance of BIPV panels to the, predictions of photovoltaic simulation tools. The existing simulation models require input parameters that characterize the electrical performance of BIPV panels subjected to various meteorological conditions. This paper describes the experimental apparatus and test procedures used to capture the required parameters. Results are presented for custom fabricated mono-crystalline, polycrystalline, and silicon film BIPV panels and a commercially available triple junction amorphous silicon panel.