Abstract: A vibration-based power generator has a variable stiffness oscillator connected to a base. The oscillator comprises an inertial mass moving relative to the base in response to vibrations. The oscillator has a neutral position corresponding to a position of the oscillator when no vibrations are transmitted to the base. The oscillator has a first position where the mass is at a first distance and a second position where the inertial mass is at a second distance from a position of the mass when the oscillator is in neutral position. The second distance is greater than the first distance. A stiffness of the oscillator at the second position is greater than a stiffness of the oscillator at the first position. A transducer generating electric power in response to movement of the inertial mass is associated with the oscillator. A method of optimizing a vibration-based power generator is also presented.