This disclosure describes techniques and systems for extracting energy from the endocochlear potential (EP) in animal subjects (e.g., human subjects) and using the extracted energy to operate circuits (e.g., electronic device, sensors, and transmitters). The subject matter of this disclosure is embodied, for example, in a system for extracting energy from an endocochlear potential of an animal, wherein the system includes a pair of electrodes, and a circuit coupled to the pair of electrodes. The circuit includes a boost converter, an energy buffer component configured to receive voltage from the boost converter, a start-up rectifier configured to provide voltage to the energy buffer component, and a control component configured to provide control signals to the boost converter. The power extracted from the endocochlear potential is equal or larger than the quiescent power of the circuit.