The electrical cell-to-module (CTM) loss for a photovoltaic (PV) module excluding the optical loss is analyzed and a mathematical model is proposed to predict the output of the module due to CTM loss. The model is obtained based on the equation that was released to the output characteristics of a partially shaded module. The electrical CTM loss is predominantly affected by two key factors, the resistance of the soldered interconnection ribbon and mismatching solar cells. We suppose that all carriers of a solar cell exposed to light are generated at half the length of the soldered interconnection ribbon and pass through the interconnection ribbon, which is in contact with both surfaces of the solar cell. The mathematical model for the electrical output of the solar cells soldered with the interconnection ribbon is completed under these assumptions. The reasons for the mismatching loss of the solar cells in the module are the photocurrent, the series resistance and the shunt resistance, which are applied to the proposed equation. The mathematical model is validated by comparing the calculated results from the newly proposed equation with the measured data of the manufactured module. The absolute error of maximum power between these results is less than 2.45%. (C) 2014 Elsevier Ltd. All rights reserved.