In a solar panel array that includes a string of series-connected panels, the load current flowing through the string is measured. The peak current (Ipp) of a panel in the string is determined. A current equal to the difference of the load current and the peak current (Ipp) is generated in a current source connected across the output terminals of the panel. The panel is thereby operated at its maximum power point (MPP). To determine the peak current (Ipp) of the panel, the magnitude of current flowing through the panel is iteratively changed and the corresponding power generated by the panel is computed. The change in the current through the panel and the measurement of the corresponding power are repeated until a maximum power is determined as being generated by the panel. The maximum power corresponds to the maximum power point (MPP) and the peak current (Ipp) of the panel.