NOVELTY - A paralleling power circuit (108) powers a load (102) from a photovoltaic array (104) and an alternate power source (106) concurrently. A control module (116) alters power that paralleling power circuit receives from alternate power source while paralleling power circuit continues to power load from both photovoltaic array and alternate power source concurrently. The control module determines an operating point of photovoltaic array from sensor data, the operating point reached in response to alteration of amount of power that paralleling power circuit receives from alternate power source.    USE - System for determining operating points of photovoltaic array or solar panel.    ADVANTAGE - Maximum power point tracking can determine an optimum operating point based on current and voltage pairs included in one or more current-voltage (I-V) curves of photovoltaic array. The characteristics of the I-V curve of photovoltaic array can be determined without disconnecting power to the load. The photovoltaic array can operate at the maximum power point over time, even as the characteristics of the photovoltaic array change. The amount of power supplied by alternate source can be adjusted and the amount of current provided to the battery can be adjusted, so that the operating point of the photovoltaic array can be moved along the I-V curve of the photovoltaic array. A calibration table can be rendered and stored in a computer readable medium or database with the current and voltage values detected as the operating point moves along the I-V curve. The current from photovoltaic array can be delivered to load and a battery concurrently. The amount of current provided to the battery can be adjusted so that the operating point of photovoltaic array can be moved along the I-V curve of the photovoltaic array. The maximum power point tracking can optimize the output of solar panel or photovoltaic array.    DETAILED DESCRIPTION - An INDEPENDENT CLAIM is included for method for determining operating points of photovoltaic array.    DESCRIPTION OF DRAWING(S) - The drawing shows a block diagram of the calibration system in which load is powered by both photovoltaic array and alternate power source concurrently during calibration.    Load (102)    Photovoltaic array (104)    Alternate power source (106)    Paralleling power circuit (108)    Control module (116)