Why are PQP test failures increasing? A look at PV module reliability
We’ll start with the good news: The photovoltaic (PV) modules undergoing Kiwa PVEL’s Product Qualification Program (PQP) this year are showing higher energy yields, and lower power loss in many of our tests.
As published in the 2026 PV Module Reliability Scorecard, energy yields in measured PAN results continue to increase, confirming that modern modules not only have higher power, but are also generating more energy throughout the day. Additionally, we noted that post-test power loss decreased across multiple tests, most notably in Potential Induced Degradation (PID) and Ultraviolet Induced Degradation (UVID) testing. Just two years ago, these test results were causing alarms in the industry, but have since shown improvement.
At the same time, the 2026 Scorecard‘s latest results included record-high failure rates. PQP testing revealed that 87% of manufacturers and 61% of bills of materials (BOMs) experienced at least one failure, the highest rates ever reported in the Scorecard’s history.
The results are curious: Why are modules experiencing lower power loss, yet failing more often?
Taking a closer look at the way the PQP failures have evolved is a good place to start.
Failures are widespread and growing
The rise of field failures continues to be a major area of concern for the solar industry, with reported instances of spontaneous glass breakage, frame structural failures, and severe weather events increasing. Likewise, our PQP failure rates from the lab have been trending upward for several years.
Kiwa PVEL now reports that failures are occurring across nearly every test sequence, signaling a systemic issue with module quality and reliability. The main source of failures this year was once again module breakage, with 60% of manufacturers having at least one failure in that category. However, delamination surged sharply, with 45% of manufacturers having at least one major delamination defect. Both of these defects are shown in Figure 1 under “Visual.”
Additionally, 21% of manufacturers had at least one junction box (JB)-related failure, including 17% of manufacturers with bypass diode failures, 9% of manufacturers with a safety failure linked to the JB, and 4% of manufacturers with JB covers falling off. These failures indicate that reliability challenges are now becoming less about traditional degradation mechanisms and more about manufacturing quality issues. As manufacturing has diversified over the past few years, and with an increased push toward larger modules and thinner materials, there needs to be a renewed focus on quality and control in the manufacturing process.
Cost, efficiency gains introduce fragility
PV manufacturers continue to face intense pricing pressure as they compete to increase module efficiency. As a result, many have reduced material consumption through thinner encapsulants, thinner frames, and lighter overall module designs. While these changes can lower costs and improve performance metrics, they also introduce quality issues.
The Scorecard highlights several examples of these tradeoffs. Zero-busbar (ZBB) designs, for instance, offer meaningful efficiency improvements and manufacturing advantages, but testing results indicate they can exhibit wider degradation ranges and heightened susceptibility to connection-related failures during Thermal Cycling (TC). While ZBB innovations reduce silver consumption and boost module efficiency, these BOMs have a wider range of TC power loss (0.6% to 8.4%) than those BOMs utilizing traditional cell busbars.
Reducing encapsulant thickness is another common cost‑cutting measure adopted by manufacturers, but this also raises reliability risks. For example, over 70% of BOMs with greater than 2% power loss following TC600 used front encapsulants with area weight in the lower quartile range. Thicker encapsulants are more forgiving under the extreme temperatures of TC testing. As electrical connections become more complex and tolerance windows narrow, modules may become less forgiving under repeated thermal and mechanical stress. Efficiency gains achieved through material optimization must be balanced against quality requirements.
Module breakage remains the industry’s primary failure mode
Despite advances in module technology, glass breakage continues to be the most common cause of PQP failures. Mechanical Stress Sequence (MSS) and Hail Stress Sequence (HSS) testing consistently reveal significant levels of damage, making structural durability one of the industry’s most persistent challenges.
Kiwa PVEL identifies module breakage during MSS and HSS testing as the combined leading failure mode across PQP results. The 2026 Scorecard findings indicate that thinner frame designs can dramatically increase breakage susceptibility by reducing overall module stiffness and transferring additional stress to the glass laminate. This phenomenon, often described as glass pinch or stress transfer, becomes increasingly problematic as module formats grow larger (see Figure 2 for MSS test results).
Hail durability is another area of concern. Overall, 23% of BOMs experienced an HSS failure. As modules grow in size and employ thinner materials, traditional designs appear less capable of handling increasingly severe impact loads. As such, 61% of 2.0 mm glass // 2.0 mm glass modules broke from 45 mm hail in our testing. The majority of “standard” modules (2.0 mm glass // 2.0 mm glass) experience glass breakage from 45 mm hail impacts, and 43% of modules with this glass thickness break from 40 mm hail impacts.
Accessing individual BOM hail test reports remains important for sites in hail-prone regions, as testing shows that meeting standard certification requirements does not necessarily guarantee durability during real-world hail events.
Delamination emerges as a major reliability concern
While breakage remains the top failure mode, delamination is quickly becoming a close second. In the 2026 Scorecard, we found 45% of manufacturers experienced at least one delamination failure in the most recent year of PQP testing, representing a substantial increase from prior years. Delamination defects were identified across multiple test sequences, including damp heat (DH), TC , and PID.
The range of affected tests suggests that the root causes extend beyond a single module design deficiency. Instead, the data point toward a combination of material selection decisions and manufacturing execution issues. Encapsulant chemistry, including EPE- and POE-based constructions, along with lamination process quality, appear to play a significant role in determining long-term adhesion performance.
Delamination is considered a major defect when those bubbles/delamination reduce electrical creepage distances to less than the minimum specified in IEC 61730.
This example in Figure 3 was one of those cases, where two BOMs from the same module manufacturer suffered significant delamination despite the use of two different encapsulant types.
Perhaps the most important takeaway is that delamination is no longer simply a BOM selection issue. Manufacturing consistency, process control and quality assurance practices now exert a comparable influence on field reliability. Even a well-designed BOM can experience failures if lamination processes are not tightly controlled.
There’s plenty more! Continue reading this story in the digital version of Solar Builder Q3 2026.
Tristan Erion-Lorico is VP of sales and marketing at Kiwa PVEL. Learn more about the company’s Product Qualification Program by contacting pvel@kiwa.com.
