A micropower Maximum Power Point Tracker (μMPPT) suitable for use in low power applications to maximize the power output for a solar-power cell array. In one embodiment, a μMPPT comprises an electrical circuit which includes a microprocessor/microcontroller used to execute the μMPPT control algorithm, and a modulator controller to control the pulse width or frequency to a high speed switch. In addition, the electrical circuit may include an analog-to-digital (A/D) converter usable to measure the input voltage from a connected solar array, the current through an inductor of the circuit, and the voltage of an attached energy store/load. In another embodiment, the μMPPT may operates in at least two modes depending on the energy store/loads conditions.