Solar photovoltaic modules (SPVMs) are projected to provide a significant portion of the electrical grid supply in the future as the world transitions toward zero-carbon energy generation. Considering its growing importance, proper quality assurance and condition monitoring of SPVM are crucial. Currently, there are several inspection methods available. However, they have downsides such as the inability to detect flaws beyond cell level, low accuracy, and inefficiently slow measurement process. Therefore, this work aims to develop an efficient technique capable of detecting defects in the entire part of SPVM. The work started with a completely open mind, using the available ultrasonic and signal processing tools in the laboratory to select a workable approach to tackling this challenge. The selected technique is based on ultrasonic guided waves (UGW), namely Lamb waves, that have been known to be useful for flaw detection in plate-like structures. Although SPVM is a plate-like structure, its geometric and material features are unique in that some aspects have not yet been addressed in other Lamb waves investigations. Therefore, a thorough study to understand the waves’ behavior in the structure is essential before delving into an investigation of the interactions between waves and defects. The primary outcome of this work is a practical technique to extract damage indicators in the response UGW signal and exploit them to determine the type and severity of defects present in the SPVM.