While 19 manufacturers received recognition as high achievers in RETC’s 2026 testing sequences, problems with ultraviolet-induced degradation in solar modules persist, while failing “red flag” scores increased in tests for damp heat and thermal cycling.
US-headquartered independent testing laboratory RETC has released its 2026 PV Module Index report, a document that contains the results of the company’s module reliability and performance testing, as well as in-depth discussions of factors in the modern solar industry that have led to the outcomes evident in the test results.
Major findings include a persistent problem of ultraviolet light-induced degradation (UVID) in solar modules, an increase in failures during tests for reliability under damp heat and thermal cycling conditions, and a significant reduction in the number of manufacturers whose modules qualify for high achievement in hail durability testing.
Each test is conducted on multiple modules in the same model line. Each model is known as a “bill of materials,” or BOM. In total, 11% of the BOMs tested for damp heat exhibited a failure condition (greater than 5% power loss), compared to just 6% the year before, while 8% failed UVID testing.
