A response to the questions raised by Alexe et al. concerning nanowire-based nanogenerators is presented. Evidence is given about the existence and detection of a piezoelectric potential in ZnO nanowires. The role played by the piezoelectric potential is to overcome the threshold voltage at the Pt–ZnO junction, while the observed output signal of ∼10 mV is the difference in Fermi levels between the two electrodes. The measurement system used by Alexe et al. is questioned, as is their model.