We compare the performances of vibration-powered microelectromechanical system (MEMS) electrical generators using a (PZT) material. With the aid of a finite element method simulation, we have designed a PZT cantilever-based energy-harvesting system that uses mechanical vibration. We fabricate cantilevers on the MEMS scale with an integrated variable Si proof mass to obtain a low resonant frequency and high current. Based on simulation results, we fabricate cantilever devices with integrated Si proof masses with volumes of about 0.32 and . These devices compare favorably to the data obtained through simulation. Further, by comparing variable mass volumes, we obtain a high current and low resonant frequency. Similar results are obtained by simulation and experiment. Therefore, we offer a new and predictable means of obtaining a low resonant frequency for application to a micropower source area. Furthermore, from the size effect of the proof mass volume, we obtain the current and resonant frequency of these energy harvester systems. The possibility of a MEMS-scale power source for energy conversion experiments is also tested.