Prediction of energy production is crucial to the design and installation of the building integrated photovoltaic systems. This prediction should be attainable based on the commonly available parameters such as system size, orientation and tilt angle. Several commercially available as well as free downloadable software tools exist to predict energy production. Six software models have been evaluated in this study and they are: PV Watts, PVsyst, MAUI, Clean Power Estimator, Solar Advisor Model (SAM) and RETScreen. This evaluation has been done by comparing the monthly, seasonaly and annually predicted data with the actual, field data obtained over a year period on a large number of residential PV systems ranging between 2 and 3 kW dc . All the systems are located in Arizona, within the Phoenix metropolitan area which lies at latitude 33° North, and longitude 112 West, and are all connected to the electrical grid.

Central. He is currently completing his Master's degree in Alternative Energy Technologies at ASU. ASU-PTL is the only accredited design qualification laboratory in the United States. ASU-PTL has tested more than 3000 PV modules and issued more than 280 qualification certificates. ASU-PTL participates in the development of national and international standards of ASTM, IEEE and IEC.