Accurate description of the electrical behavior of organic solar cells (OSCs) becomes necessary with the advance of OSC technology toward up-scaled modules. We propose here a compact model for OSCs, by identifying different regimes present in the device operation in dark and under light: OFF, exponential sub-VON, power-law above-VON, and photocurrent. We also present a complete parameter extraction method for the model. In addition, we discuss the effect of the resistivity of transparent electrode and the device size on the OSC performance, by illustrating expected modifications on the current- voltage curve and parameter values.