We designed an electrical power loss model to minimize the electrical power losses in large-area monolithic organic photovoltaic (m-OPV) modules. Using the electrical power loss model, we calculated the parasitic electrical power losses on the transparent conductive oxide layer by considering the series resistance and shading losses. We fabricated a unit organic photovoltaic (OPV) cell as a reference and extracted its electrical parameters such as voltage and current density under the maximum power output condition. We calculated the electrical losses using the proposed electrical power loss model by applying these extracted parameters of the unit OPV cell. From the results of the electrical power loss model, the pattern length of the active area of a single OPV cell was determined to be 9 mm, indicating that we can place seven OPV cells in an active area of 84 mm x 90 mm. (c) 2010 Elsevier B.V. All rights reserved.