Microelectromechanical system of electrostatic energy harvesters is modeled using a nonlinear state–space approach in this research. The analytical models of in‐plane overlap, in‐plane gap closing, and their compound structures are used to analyze the energy harvesting performance from heartbeats‐generated vibrations. The detailed models of both electrical and mechanical subsystems including stopper function, motion drag, parasitic capacitors, and energy converter capacitors are developed in the format of state–space equations. To reach the optimal heartbeat energy harvesting, typical 1D harvesters are developed and allowed to move inx–yandx–y–zdirections. Accordingly, the optimal harvester combines the features of in‐plane overlap and in‐plane gap closing energy conversions, and so allows efficient absorption of energy released by heartbeat in different directions. This 3D feature gives a considerable rise to power generation to 35.038 μw at the same size compared to the new rate of the in‐plane overlap or in‐plane gap‐closing electrostatic harvesters individually.