What’s in a module

PV modules with the exact same model type and datasheet can be manufactured from completely different bills of materials (BOMs). Module manufacturers are able to mix-and-match integral materials, using different glass, different encapsulant, and even different cells, as long as all the components are listed in the manufacturer’s certification reports. Kiwa PVEL’s test results from the lab and field have shown how individual PV module components can dramatically affect module performance and reliability, and how certification testing is not sufficient to differentiate levels of long-term module reliability for project investors.

While individual BOMs are not marketed to buyers, the detailed PQP reports clearly document the BOMs of each model that performed well in testing. Kiwa PVEL’s downstream partners can leverage PQP reports to specify well performing BOMs in their supply agreements.


PQP Testing of PV Module Reliability and Performance

Kiwa PVEL’s PV Module PQP is a comprehensive protocol of lab and field tests that assess the bankability of PV modules. While the specific tests have changed over time, the same four principles have guided Kiwa PVEL’s PQP since it was first established in 2012:

  • Empirical Data

The PQP provides empirical data for revenue and energy yield modeling.

  • Standard Processes

The PQP tests all BOMs consistently, using calibrated equipment overseen by Kiwa PVEL’s experts via testing at Kiwa PVEL’s facilities in California, USA, or at Kiwa PI China, in Suzhou, China.

  • No Hand-picked Samples

Kiwa PVEL’s inspectors witness the production of all test samples and record BOM details.

  • Regular Program Updates

Kiwa PVEL implements biennial PQP test sequence updates targeting new technologies and manufacturing techniques.

PQP Module Flow Test Chart - Watermark V2.png

Why BOM-Level Testing is Important

Taken from the 2023 PV Module Reliability Scorecard.

As of 2023, Heliolytics (now part of Zeitview) had conducted 155 GW of aerial scans, which collectively determined that the module model type is indicative but not sufficient for understanding module reliability risks. This example shows two adjacent modules that are the same model type but clearly different cells and likely other BOM components. The module on the right is performing as expected, but the one on the left has evidence of busbar discoloration. This can lead to module-level degradation, as well as differential degradation within the array, thus amplifying mismatch losses and further impacting site performance.

Why PQP Testing is Important – Warranty and Certification Limitations

Certifications and warranties are important prerequisites for global market acceptance and financing of solar PV technologies. However, certifications do not ensure the reliable long-term performance of modules in the field, and warranties do not provide full protection from financial losses when modules fail or degrade.

Challenges with Warranties

Taken from the 2020 PV Module Reliability Scorecard.

  1. Solvency and responsiveness

Warranties do not protect buyers when manufacturers become insolvent or are unresponsive to claims.

  1. Imprecise measurement

Measuring power degradation in the field with precision is extremely difficult, so most successful warranty claims are for excessive underperformance or total failure. Warranties typically include a 3% buffer for measurement uncertainty. This 3% reduction in energy yield on top of expected annual degradation can equate to millions of dollars in lost revenue.

  1. Coverage limitations

Even when claims are accepted, warranties usually cover the cost of replacement modules only – not costs associated with labor or lost energy production. Due to manufacturing advances, suitable replacement modules may not even be available for older systems, and warranties do not cover the costs of system upgrades to become compatible with current module replacements.

Best Practices for PV Module Warranty Claims

Taken from the 2021 PV Module Reliability Scorecard.

Contributed by Mike Loeser, Strata Solar Services.

As an asset owner and third-party O&M provider for more than 3GW of solar power plants in the U.S., Strata Solar has supported dozens of PV module warranty claims across many manufacturers.

Understanding Warranty Coverage



Power output (25+ years)

Cost of diagnosis and lab testing

Workmanship (10 years)

Cost of gathering evidence

Replacement modules or cash compensation

Lost energy

Evidence and testing requirements by failure mode

Module removal and reinstallation

Filing Warranty Claims

Selectively and strategically filing claims is critical because claim submission and adjudication costs can exceed compensation from the warranty. Success requires close attention to detail at every stage of the project. Claims are more likely to be cost-effective when stakeholders:

  1. Understand the Warranty
    • Fully understand all warranty terms before internal investigations begin.
  1. Maintain Records
    • Maintain comprehensive records for all stages of a project.
      • Create site maps with module serial numbers.
      • Document maintenance granularly.
      • Log all previously replaced PV modules.
      • Store all historical testing records.
  1. Document the Warranty
    • Record and document the warranty claim process.
      • Save all communications.
      • Send memos following phone calls.
      • Continue documenting test results at the module level.
      • Update site maps as modules are removed and replaced.

Ultimately, asset owners cannot rely on warranties alone for full compensation when PV modules underperform or fail in the field.

Shortcomings of Certifications

Taken from the 2019 PV Module Reliability Scorecard.

Certifications Only Address Product Safety.

Most solar project developers and equipment buyers require two key certifications for solar PV modules – IEC/UL 61215 and IEC/UL 61730. They demonstrate that PV modules are safe. None of these test standards address long-term PV module reliability and performance in the field.

  • IEC/UL 61730 only certifies that PV modules are not hazardous to operate.
  • IEC/UL 61215 only screens for defects that would appear in the first few years of operation.
  • Manufacturers select the specific modules that are used in certification tests. It is possible to send “golden samples” that are constructed more carefully than commercially produced modules.
  • Manufacturers can change some component combinations of their module BOM without re-certifying the module model.

Additionally, updating IEC and UL standards is a multi-year process that cannot keep pace with the rate of innovation in solar PV module technology. Both standards have failed to identify major field performance issues associated with technical advances, such as Light and Elevated Temperature Induced Degradation (LETID) and Potential-induced Degradation (PID).

While IEC and UL certifications are important indicators of module safety, long-term reliability and performance are also important to PV buyers. Since its founding in 2010, Kiwa PVEL has consulted with developers and financial institutions to continually develop test programs that address specific issues observed in the field and with emerging and even proven technologies. By extending IEC 61215 sequences and incorporating additional tests, Kiwa PVEL’s PQP approximates the impact that decades of exposure in the field has on PV modules.

Each year in the PV Module Reliability Scorecard, Kiwa PVEL highlights examples of modules that do well in certification tests but do poorly during the extended and enhanced PQP tests. These serve as stark examples of why the PQP’s extended reliability testing remains a key tool for module procurement due diligence.