Single-diode model is commonly used for modeling the electrical properties of photovoltaic (PV) modules, in which the current–voltage (I–V) equation is implicit and not convenience in parameter identification and power prediction. In this article, a novel method based on the power-law model (PLM) is proposed to model and characterize the electrical properties of PV modules under various operating conditions. Due to inherent simplicity and explicit trait of PLM, I–V properties of PV module under different operating conditions are predicted without using any nonelementary functions or iterative process, which reduces the computational complexity and costs. The dependence of the parameters in PLM on solar irradiance and module temperature is derived and investigated in detail. Moreover, the dependence of shape parameters in PLM on operating conditions is discussed thoroughly for the first time. Using our method, the parameters in PLM under various operating condition are calculated and then the I–V curve is predicted accurately and effectively. The accuracy and reliability of the model are validated by massive I–V curves measured outdoor in large-scale conditions. The capability of the model is demonstrated for different types of PV modules. The proposed processes are simple and especially useful to calculate the actual performances of PV modules under operating conditions, making it scalable for direct online application.