This study investigates the effect of air humidity (% RH) on the output voltage (Voc) of a Moist Electric Generator (MEG) for three different material compositions: A, B, and C. The modeling was conducted using second- and third-order polynomial regression. Model performance was evaluated based on the coefficient of determination (R^{2}), optimal humidity (H_opt), and maximum voltage (V_max). The results show that the third-order model provides higher accuracy for all compositions. Composition \mathbf{B} yielded the highest maximum voltage of 5.40 V at 78.48% humidity, followed by compositions \mathbf{C} and \mathbf{A}. This model can serve as a foundation for the development of humidity-based MEG systems in tropical environments. © 2025 IEEE.