As fossil fuel resources decrease and their price correspondingly increases, finding a suitable alternative source of energy is a priority in all countries. This case study predicts the amount of energy that can be generated by photovoltaic cells mounted on the roof of a passenger coach moving on the Kerman–Tehran rail line in Iran under various conditions such as different months, hours and train speeds. The energy gain is calculated using an isotropic solar model and data on the levels of radiation incident on a horizontal surface at Kerman, Yazd, Esfahan, Qom and Tehran. These cities are located on the Kerman–Tehran rail route. The results show that departure time and speed of the train play a significant role in determining the amount of energy created by the photovoltaic panels.