This paper focuses on a new approach to model photovoltaic (PV) solar modules based on symmetric-shifted Gompertz functions. This solution significantly reduces the number of fitting parameters, convergence problems, and computational costs in comparison with previous modeling. The entire I-V curve is provided, as well as relevant nonlinear relations between environmental and electrical variables. A comparison with previous approaches has also been included in this paper, discussing the relevant advantages of the proposed technique with respect to previously published solutions. Real data from CdTe thin-film and Si PV power plants have been used to assess this new nonlinear model. The proposed solution can also be applied to check the active power generated by PV modules based on the expected datasheet values provided by the manufacturers. This alternative process avoids the necessity of removing and analyzing the solar modules in a laboratory environment.