Piezoelectric materials are well-utilized for transforming mechanical vibrations into electrical energy that can be stored and used to power a diversity of devices. In this work, these materials have been studied to improve the efficiency of a piezoelectric system, whereby the shape and vibration mode of a piezoelectric module was changed. The basic shape of the piezoelectric module used in this work comprises a width of 10 mm, a length of 30 mm, and a thickness of 0.2 mm. The structural design of the piezoelectric module is optimized using a Taguchi method to increase the corresponding electrical-energy generation. The maximum terminal voltage was defined as a characteristic value to evaluate the optimal design parameters. Through this work, we propose an optimal structure with an eccentric and centric mass; furthermore, the voltage increase of approximately 26% was obtained by comparing a general plate-vibrating piezosystem with an optimal plate-vibrating piezosystem.