One of the main concerns of module manufacturers is the power loss that takes place when the solar cells are incorporated in PV modules. This power loss, known as cell-to-module (CTM) loss, results from the influence of many factors which occur during module production. Some of these factors lead to a gain in power at the end of the process; on the other hand, some are responsible for a loss of power and offset the positive effects of other ones, resulting in a net power loss. In this paper the CTM losses will be addressed from an industrial point of view and for standard crystalline PV modules. The focus will first be on some of the most frequent issues detected in production lines and their influence on module power loss. More extensive research is then carried out to arrive at an explanation of their origin. This paper describes some of the mentioned factors along with the different ways of detecting them.