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In evaluating the energy-generation potential of a photovoltaic (PV) energy system, the system is usually assumed to work without interruptions over its entire life. PV energy systems are fairly reliable, but as any complex system, they may fail. In PV systems, the inverter is responsible for the majority of failures, and most inverter failures are blamed on the aluminum electrolytic capacitors typically used in the dc bus. This paper investigates the effects of common failure modes on the reliability of PV inverters and suggests a model framework for decomposing the inverter into subsystems for more detailed study. The challenges of statistical analysis based on small data sets are discussed, and simulations are performed to illustrate the proposed model using a simple decomposition into subsystems of the inverter used in the 342-kW PV system at the Georgia Tech Aquatic Center. Index Terms--Photovoltaic (PV) power systems, power-system reliability, power-system simulation, reliability modeling, simulation.