In this paper, using an extended version of the 1-diode/2-resistors (1D & 2R) circuit model, we propose a methodology suitable for modeling Photovoltaic Solar Cells (PVSCs) operating in indoor environments. With low-cost equipment and low-complexity procedures, this methodology finds an equivalent circuit that reproduces the worst-case performance of a harvester based on indoor PVSCs for a continuous illuminance range at room temperature. This methodology is validated using a commercial indoor PVSC that has been tested for several illuminance levels at a room temperature and warm white LED (light-emitting diode) spectrum. The extracted model achieves a mean absolute percentage error (MAPE) of 4.85% for the illuminance ranging from 177 to 33.3 x 10(3) lm/m(2). Furthermore, this model achieves a MAPE of 0.57% at maximum power point (MPP), and a MAPE of 2.07% around the MPP.