A power management system, comprising: a control system configured to monitor the actual power output (28, 68) of a photovoltaic system comprising one or more arrays of photovoltaic modules and to generate an actual power output measurement of the photvoltaic system; and a processor-based device programmed with a model for estimating power output of the one or more arrays of photovoltaic modules, and configured to: receive input signals (24, 54) representing inputs defined by the model, the inputs corresponding to values of known parameters and/or measured parameters of the photovoltaic system; use the model to calculate an estimated power output (60, 62) of the one or more arrays of photovoltaic modules and of each of the photovoltaic modules based on the input signals; compare the estimated power output for the one or more arrays of photovoltaic modules to the generated actual power output measurement (28, 68) received from the control system; repeatedly adjust the input signals, so as to vary values of the inputs defined by the model with respect to one or more photovoltaic modules or groups of modules and generate multiple scenarios/instances of adjusted input values that achieve adjusted estimated power outputs that match the actual power output measurement (28, 68) of the one or more arrays of photovoltaic modules; and identifying a source of power loss within the photovoltaic system based on scenarios/instances of the adjusted input values generated by the model. a control system configured to monitor the actual power output (28, 68) of a photovoltaic system comprising one or more arrays of photovoltaic modules and to generate an actual power output measurement of the photvoltaic system; and a processor-based device programmed with a model for estimating power output of the one or more arrays of photovoltaic modules, and configured to: receive input signals (24, 54) representing inputs defined by the model, the inputs corresponding to values of known parameters and/or measured parameters of the photovoltaic system; use the model to calculate an estimated power output (60, 62) of the one or more arrays of photovoltaic modules and of each of the photovoltaic modules based on the input signals; compare the estimated power output for the one or more arrays of photovoltaic modules to the generated actual power output measurement (28, 68) received from the control system; repeatedly adjust the input signals, so as to vary values of the inputs defined by the model with respect to one or more photovoltaic modules or groups of modules and generate multiple scenarios/instances of adjusted input values that achieve adjusted estimated power outputs that match the actual power output measurement (28, 68) of the one or more arrays of photovoltaic modules; and identifying a source of power loss within the photovoltaic system based on scenarios/instances of the adjusted input values generated by the model. receive input signals (24, 54) representing inputs defined by the model, the inputs corresponding to values of known parameters and/or measured parameters of the photovoltaic system; use the model to calculate an estimated power output (60, 62) of the one or more arrays of photovoltaic modules and of each of the photovoltaic modules based on the input signals; compare the estimated power output for the one or more arrays of photovoltaic modules to the generated actual power output measurement (28, 68) received from the control system; repeatedly adjust the input signals, so as to vary values of the inputs defined by the model with respect to one or more photovoltaic modules or groups of modules and generate multiple scenarios/instances of adjusted input values that achieve adjusted estimated power outputs that match the actual power output measurement (28, 68) of the one or more arrays of photovoltaic modules; and identifying a source of power loss within the photovoltaic system based on scenarios/instances of the adjusted input values generated by the model.