ABOUT THIS BOOKSolar photovoltaic (PV) technology has moved from a peripheral generation option to a structural element of the modern electricity system. This shift in scale changes the central analytical question. When PV occupies only a marginal share of electricity supply, the dominant concern is deployment. Once PV becomes deeply embedded in the power system, however, the more consequential question is whether the installed fleet can deliver energy dependably over long operating lifetimes and under diverse field conditions.