This book describes the conceptual, scientific and mathematical processes used to estimate the power and energy production of grid connected PV systems. It outlines the logical sequence of modeling steps that describe the chain of events by which sunlight is captured and converted into electrical energy that is ultimately fed into the electrical grid. At each modeling step the authors fully document the available models and describe their use, data requirements, advantages and disadvantages. They also summarize the available evidence for the various models’ credibility and accuracy. By providing this information within a system perspective, the book provides a unique level of transparency, clarity and rigor.