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.
While 5% of BOMs exhibited failures in the thermal cycling test sequence (up from 2% in 2025), 92% met the threshold for high achievement. This could indicate that a component chosen by a single manufacturer is to blame for the failure.
Only 25% of BOMs were recognized as high achievers in hail durability testing, down from 70% the year before. Because this testing is optional, RETC did not define a failure condition, but noted that while most PV module designs can meet baseline ballistic impact standards recent catastrophic losses due to hailstorms suggest that more robust standard is necessary.
Recognizing high achievers
For 2026, RETC recognized 19 solar module manufacturers for high achievement in at least one test, and 13 manufacturers as Overall Highest Achievers, signifying they met standards in a certain number of tests for reliability and performance.
Manufacturers recognized as Overall Highest Achievers in the 2026 report are Imperial Star Solar, JA Solar, JinkoSolar, Longi Solar, Qcells, Runergy, SolarSpace, Thornova Solar, Trina Solar, VSUN Solar, TW Solar, Waaree and Yingli Solar.
How RETC tests modules
RETC gleans much of the data it uses to evaluate manufacturers through its Thresher Test, a series of eight test sequences, with six sequences dedicated to module reliability and two for performance testing.
Thresher test sequences in the reliability discipline include:
Thresher test sequences in the performance discipline include:
In addition to the Thresher test sequences, RETC evaluates solar modules based on their performance on its hail durability test (HDT), as well as tests it conducts to certify products for meeting California Energy Commission (CEC) standards.
In total, each of the disciplines has seven tests in which products can be recognized for high achievement.
Levels of achievement
RETC recognizes manufacturers for their products’ scores on the testing regimen at the following four levels: Overall Highest Achiever, Reliability High Achiever, Performance High Achiever and Test Category High Achiever.
Overall Highest Achiever status is awarded if the manufacturer’s products earn high achiever recognition in both of the disciplines, and have their test samples witnessed and bills of materials verified by an independent third party.
Reliability High Achievers are manufacturers whose products exceed standards on at least 3 of the 7 tests in the reliability discipline (glass-on-backsheet models must exceed standards on the BUDT test and 3 additional tests). All of the above-listed companies qualified for this recognition in this year’s report.
Performance High Achievers are manufacturers whose products exceed standards on at least 3 of the 7 tests in the performance discipline. As before, all of the above companies qualified. Alps Solar was also recognized.
Test Category High Achiever status is awarded to manufacturers whose products exceed the high achiever standards on any single test. For 2026, the list includes Adani Solar, Auxin Solar, Illuminate Solar, Mission Solar, and Silfab Solar.
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