One important issue not reported in the literature is to determine the impact of a high-voltage (HV) power transmission line on the power production of a photovoltaic (PV) module located near the power transmission line. Since grid-connected PV power generation systems are generally located near HV power transmission lines, this issue becomes even more crucial. For the first time, this research work addresses this issue by presenting a novel comprehensive theoretical analysis and providing relevant experimental verifications. The outcome of this study demonstrates that the electric field of the electromagnetic (EM) wave produced by a HV power transmission line has no influence on the output power of a PV module located near the power transmission line, while the magnetic field of the EM wave has a huge negative impact on the output power. Moreover, this impact intensifies when the current of the power transmission line becomes larger to respond load demand, and declines by increasing the distance between the PV module and the conductors of the power transmission line. Finally, to high efficiently utilize PV power generation systems, a minimum distance of 200 m between PV panels and HV power transmission lines is recommended.