Triboelectric nanogenerator (TENG) uses charge transfer between two asymmetric charge affinity materials such as metal and dielectrics. Metal electrode acts as charge collector from dielectrics and acts as charge transfer path to an external load, which model deals with only a net charge of metal electrode concerning electrical output. In this work, we found that metal electrode in triboelectric generator has non-negligible surface charge polarization causing open-circuit voltage difference in the model TENG system. The output voltage depends on the initial preparation conditions of the TENG for I–V measurements, even for the same measured charge densities. The measured output voltage difference with the same charge density implies that electric charges of TENG are composed of movable charges that affect current and voltage output and the bounded fixed charges that only affect open-circuit voltage.