If the answer was yes, that carried significant weight. Certification to established international and U.S. standards remains fundamental to solar quality assurance because it confirms that a representative product has met defined safety and performance requirements.
But utility-scale solar has changed.
Projects are larger. Asset owners manage broader portfolios. Operating lives can extend beyond thirty years. Financing structures have become more sophisticated, and the consequences of equipment underperformance can affect millions of dollars in production and investment returns.
In this episode of The Solar Coaster, Anna Covert and Alex Herrera examine why solar buyers are increasingly looking beyond baseline certification toward independent durability testing, bill-of-materials verification, manufacturing oversight, and continuous product qualification.
Certification Is the Foundation, Not the Entire Building
Certification answers an important question: did a representative product meet a defined standard at the time it was tested?
What it does not necessarily tell a buyer is whether every later manufacturing run, supplier substitution, material change, or production variation still reflects the exact configuration originally evaluated.
That distinction matters because solar modules are not frozen in time.
Glass suppliers can change. Encapsulants can change. Cells, frames, backsheets, sealants, and manufacturing processes can change. A model number may remain the same even as elements inside that product evolve.
This is why buyers increasingly look at solar quality as an ongoing evidence trail rather than a one-time certification event.
Bill-of-Materials-Specific Testing Changes the Question
The concept of bill-of-materials-specific bankability testing sounds technical, but the principle is straightforward.
Instead of evaluating a solar module only as a generic model number, testing is tied to a particular construction: the glass, encapsulant, cells, frame, backsheet, and other critical components actually being purchased.
The goal is to understand how that specific combination behaves under stress beyond the minimum sequences required for baseline certification.
This is becoming especially important in today’s increasingly precise commercial and utility-scale solar market, where relatively small differences in performance can materially affect project economics.
A Supplier Change Can Become a Project-Level Problem
One of the examples discussed in the episode involved a two-phase solar project in which modules were represented under the same bill-of-materials designation.
After commissioning, one phase reportedly experienced glass breakage of roughly one percent, while another approached fifteen percent.
When spare modules were evaluated, a much larger share of samples from the higher-failure phase failed testing. The issue was ultimately associated with a change in the glass supplier.
The example illustrates an important procurement lesson: two products can appear equivalent on paper while behaving differently in real operating conditions.
If a material or critical supplier changes after qualification, buyers may reasonably want evidence that the new configuration still supports the same expected durability.
Why Finding Problems Before Installation Matters
Post-installation investigations can identify failure mechanisms, but by the time those investigations begin, asset owners may already be facing replacement costs, operational disruptions, energy losses, warranty claims, and uncertainty about the rest of the fleet.
The better opportunity is to identify meaningful manufacturing or material changes before equipment reaches the site.
That is where factory inspections, supplier verification, bill-of-materials review, and pre-shipment inspections become part of a larger quality-assurance process.
This concept fits a broader theme we have discussed throughout the changing solar supply chain: the final module is only as dependable as the components, suppliers, manufacturing controls, and verification systems behind it.
What Extended Durability Testing Can Measure
Extended testing can include several different stress sequences depending on the program and intended project environment.
Examples discussed in the episode include thermal cycling, damp heat, humidity-freeze exposure, mechanical loading, potential-induced degradation, ultraviolet exposure, and hail impact testing.
Each test evaluates something different.
Thermal cycling repeatedly expands and contracts materials. Damp heat can reveal vulnerabilities important in hot and humid environments. Mechanical loading can provide insight into performance under wind or snow pressure. Hail testing becomes particularly important in severe-weather markets.
The purpose is not to perfectly recreate every condition a module will experience over thirty years.
The purpose is comparison.
Testing gives developers and engineering teams another way to distinguish between products and constructions that may otherwise look very similar on a specification sheet.
There Is No Single Best Module for Every Project
A product that performs exceptionally well in one category may not necessarily be the ideal choice in every environment.
In hail-prone markets, impact resistance may carry greater weight. In hot, humid climates, extended damp-heat and thermal-cycle performance may receive more scrutiny. Projects exposed to heavy snow loads or high winds may emphasize mechanical integrity.
This is an important evolution in solar procurement.
The question is no longer simply whether a module is good.
The better question is whether that module is appropriate for the specific environmental and financial risk profile of the project where it will operate.
Independent Data Is Becoming a Commercial Advantage
For manufacturers, recognized independent durability testing is increasingly more than a technical exercise.
It can directly influence procurement.
A manufacturer that enters a sourcing discussion with recognized testing tied to a clearly documented bill of materials can move more quickly into conversations about price, schedule, project fit, and delivery.
A supplier without that evidence may instead need to spend valuable time answering additional engineering questions or commissioning testing while competitors are already moving through procurement.
In a market with compressed development schedules, that delay can become a competitive disadvantage.
Bankability Is Ultimately About Uncertainty
The term bankability becomes particularly important when solar projects are financed to operate for decades.
Investors, lenders, developers, independent engineers, and asset owners all want confidence that the equipment supporting a project’s financial assumptions will continue performing as expected.
Independent durability data cannot eliminate uncertainty entirely.
But it can reduce it.
And when uncertainty decreases, procurement decisions, engineering reviews, and financing discussions can become more efficient.
This matters particularly for utility-scale solar projects, where even relatively small performance differences become significant when multiplied across thousands or millions of modules.
Approved Vendor Lists Are Becoming More Dynamic
Large developers and asset owners frequently maintain approved or pre-qualified manufacturer lists.
Historically, certificates and specification sheets may have carried much of the qualification burden.
Today, buyers increasingly want evidence tied not only to the manufacturer but to the exact product configuration being supplied.
Approved vendor lists therefore cannot necessarily remain static indefinitely.
They may be revisited when manufacturers introduce new products, when critical suppliers change, when bills of materials are modified, or when new field-performance information becomes available.
Field Performance Reinforces the Need for Better Validation
The episode also discusses broader photovoltaic fleet-performance data showing why buyers remain focused on the relationship between expected and actual production.
These numbers do not necessarily identify one single cause. Differences can result from forecasting assumptions, equipment performance, environmental conditions, operations, or combinations of several factors.
But the larger lesson remains important.
If the financial model depends on decades of reliable energy generation, then procurement needs enough evidence to support those assumptions.
The New Solar Quality Model Is Layered
The emerging approach to solar module procurement is increasingly layered.
Baseline certification establishes compliance. Bill-of-materials-specific durability testing evaluates a particular construction. Factory and supplier oversight help confirm that manufacturing continues to reflect what was qualified. Pre-shipment verification helps confirm that the equipment leaving the factory matches what the buyer agreed to purchase.
Each layer answers a different question.
Is the module compliant?
How does this specific construction perform under stress?
Is the factory still producing what was qualified?
And is the shipment arriving at the project consistent with the purchasing agreement?
Certification Is the Floor
None of this means certification has lost its importance.
Quite the opposite.
Certification remains the foundation of product qualification.
What has changed is the scale and sophistication of the market around it.
As solar becomes a larger component of global energy infrastructure, buyers are increasingly treating equipment reliability as an ongoing evidence problem rather than a one-time paperwork exercise.
For developers and asset owners, the practical takeaway is simple: ask what bill of materials was actually tested, whether critical suppliers have changed, what independent durability data exists, and whether the product being delivered still reflects the assumptions behind the original purchasing decision.
The question is no longer simply, “Is this module certified?” It is, “Do we have enough independent evidence to believe this exact product is the right fit for this exact risk profile?”
Explore more conversations about utility-scale solar, storage, technology, and the rapidly changing energy market at SolarCoasterBook.com.
Full Podcast Transcript:
Episode Transcript
Anna Covert and Alex Herrera discuss why solar module certification is increasingly becoming the starting point—not the finish line—for utility-scale procurement.
Anna Covert: In utility-scale solar, the old procurement question used to sound fairly simple: is the module certified? If the answer was yes, that often carried a lot of weight. Certification to international and U.S. safety standards remains essential, of course. It confirms that a product meets established safety and performance qualifications. But in today’s market, certification is no longer the end of the conversation. Developers are building larger pipelines, asset owners are managing bigger portfolios, and the financial consequences of underperformance have become much harder to ignore.
Alex Herrera: That shift is really the heart of the story. Solar buyers are not abandoning certification; they are putting it in context. A certificate tells you that a representative sample met a required baseline at a particular point in time. What it does not necessarily tell you is whether every later production run, every supplier change, or every material substitution still reflects the product that was originally evaluated. For a multi-gigawatt developer, that difference can be enormous.
Anna Covert: Exactly. Certification confirms a minimum. It does not always confirm a match between a specific module and a specific project’s risk profile. A project in a hail-prone region, for example, may need a different kind of evidence than a project in a hot and humid climate. A project exposed to high winds or heavy structural loads may need a closer look at mechanical integrity. The module may be certified, but the buyer still needs to know whether it is the right product for the job.
Alex Herrera: And that is where bill-of-materials-specific bankability testing becomes important. The phrase sounds technical, but the concept is straightforward. Instead of treating a module as a generic model number, the testing is tied to a named bill of materials. That means the glass, encapsulant, cells, frame, and other critical inputs are part of the qualification picture. The point is to understand how that exact construction behaves under longer and more demanding stress sequences than baseline certification may require.
Anna Covert: One of the most striking examples involves a two-phase solar project where modules were represented under the same bill of materials designation. After commissioning, one phase saw a glass breakage rate of roughly one percent, while the other approached fifteen percent. That is not a small difference. When spare modules from both phases were evaluated, nearly seventy-five percent of the samples from the higher-failure phase failed. The issue was traced to an undisclosed change in glass suppliers.
Alex Herrera: That example shows why buyers are increasingly focused on continuity, not just the initial certificate. From the manufacturer’s perspective, the modules may have looked equivalent because they shared the same bill of materials designation. But in the field, the reliability outcome was materially different. The supplier change mattered. And if the change had been detected earlier, during production or before shipment, it might have triggered additional mechanical stress testing before the modules ever reached the project site.
Anna Covert: That is a key point: post-installation investigations can identify what went wrong, but by then the damage may already be expensive and disruptive. If glass starts breaking after commissioning, the buyer is dealing with replacement costs, operational headaches, possible energy losses, and a lot of uncertainty. The better opportunity is to detect material or manufacturing changes before the equipment reaches the field. Factory inspections, verification of critical materials and suppliers, and pre-shipment inspections all become part of a more continuous qualification process.
Alex Herrera: Of course, no inspection or testing program can eliminate every risk. Solar modules operate for decades in varied environments, and field performance is affected by many factors. But the combination of certification, bill-of-materials-specific bankability testing, production oversight, and pre-shipment verification gives buyers a stronger body of evidence. It helps confirm that the product being delivered still reflects the materials, construction, and performance characteristics behind the original purchasing decision.
Anna Covert: This is also changing how approved vendor lists work. Large developers and asset owners often maintain lists of module manufacturers that are approved or pre-qualified. In the past, certificates and specification sheets might have carried more of the burden. Now, buyers increasingly look for independent data on durability, bill-of-materials consistency, and long-term performance risk. They want to know not just who the manufacturer is, but what evidence supports the specific product being offered.
Alex Herrera: Independent engineers can play a major role in that review. If they recognize the testing protocol and view the resulting data as relevant to the project, procurement can move more efficiently. But if the methodology is unclear, if the tested bill of materials is not well documented, or if supporting evidence is incomplete, the manufacturer may be asked for more information or additional testing. In a market with compressed timelines, that can become a competitive disadvantage.
Anna Covert: Approved vendor lists are not static, either. They may be revisited annually, when a new product line is introduced, or when materials and suppliers change. That matters because module manufacturing is not frozen in time. Suppliers can change, materials can change, and production processes can change. A qualification decision made once, years ago, may not tell the whole story about what is being delivered today.
Alex Herrera: The growing scrutiny is tied to the scale and economics of modern solar. Projects are larger, portfolios are larger, and operating lives are expected to extend beyond thirty years. Even modest differences in reliability can affect energy production, operating costs, and investment returns. In that context, a small performance gap is not always small in financial terms. Across a large fleet, it can become very meaningful.
Anna Covert: There is also broader performance data that reinforces the need for careful validation. Data cited from the Department of Energy’s PV Fleet Performance Data Initiative showed that the median fielded system produced about ninety-eight point six percent of its weather-corrected energy estimate in 2024, compared with roughly one hundred two percent in 2020. At the lower end of the distribution, performance declined from about ninety percent of expected output to eighty-five percent over the same period.
Alex Herrera: Those numbers do not point to one single cause. Some projects may have overestimated energy production. Some may have equipment that did not meet expectations. Many may involve a combination of factors. But the trend still matters because it reminds buyers that project assumptions and equipment durability both need scrutiny. If the financial model assumes decades of dependable performance, the procurement process has to support that assumption with evidence.
Anna Covert: That brings us to what extended durability testing can and cannot do. It does not create a perfect, site-specific prediction of future performance. It cannot say, with certainty, that one module will behave a certain way in every real-world condition. Instead, it produces comparative data. It helps engineering and procurement teams see how different products and different bills of materials respond to known sources of long-term stress.
Alex Herrera: Depending on the testing program, that can include thermal cycling, damp heat, humidity-freeze exposure, mechanical loading, potential-induced degradation, ultraviolet exposure, and hail impact. Each test reveals something different. Thermal cycling can stress materials through repeated expansion and contraction. Damp heat can be especially relevant in hot, humid environments. Mechanical loading and hail impact can matter where modules face wind, snow, or severe weather risks. The goal is not to simulate every possible condition, but to reveal meaningful differences between products.
Anna Covert: For buyers managing projects across multiple regions, that comparative view is valuable. A module that looks strong in one category may not be the best fit everywhere. In hail-prone regions, hail resilience may move to the top of the priority list. In hot and humid climates, extended damp-heat and thermal-cycling performance may receive more attention. In areas exposed to high winds or heavy structural loads, mechanical integrity may be the bigger concern.
Alex Herrera: This also helps explain why market expectations have changed. A decade ago, manufacturers might commission extended testing mainly when a specific transaction required it. Today, the market is different. Global module oversupply, regulatory uncertainty, and compressed project timelines have shifted what buyers expect before serious procurement discussions begin. Increasingly, they want recognized, independent durability data up front.
Anna Covert: That has a direct commercial implication for manufacturers. If a supplier arrives with recognized, bill-of-materials-specific evidence, the conversation can move toward product fit, price, schedule, and delivery. If the supplier does not have that evidence, it may spend valuable time trying to generate documentation while competitors are already prepared. In a fast-moving procurement process, that can affect who stays in the running.
Alex Herrera: It is also worth emphasizing that this is not only about catching bad products. It is about matching products to risk. A certified module may be safe and compliant, yet still not be the best option for a particular project. Procurement teams are becoming more sophisticated because their responsibilities are broader. They are not just buying panels; they are buying long-term performance, bankability, and confidence that the asset can meet its financial expectations.
Anna Covert: And the phrase “bankability” is important here. Investors, lenders, independent engineers, developers, and asset owners all care about whether a product supports the long-term economics of a project. If the evidence is thin, uncertainty increases. If uncertainty increases, the procurement process may slow down, additional testing may be required, or the buyer may choose a product with stronger documentation. Independent durability data helps reduce that uncertainty, even if it cannot remove it entirely.
Alex Herrera: The undisclosed glass supplier change is a useful cautionary example because it shows that the risk may not be visible from the headline product name. Two phases can appear similar on paper and behave very differently in the field. That is why verification of critical suppliers and materials matters. If a module was qualified with one set of inputs, and then a key input changes, buyers may reasonably want to know whether the new configuration still deserves the same level of confidence.
Anna Covert: So, the industry is moving from one-time qualification toward ongoing verification. Certification remains the foundation, but it is no longer the whole building. The stronger approach is layered: baseline certification, extended durability testing tied to a specific bill of materials, oversight during production, and checks before shipment. Each layer answers a different question. Is the product compliant? How does this specific construction perform under stress? Is the factory still building what was qualified? Is the shipment consistent with what the buyer agreed to purchase?
Alex Herrera: That layered approach is especially relevant as solar becomes a larger part of energy infrastructure. When projects are small, a performance problem is still painful, but the scale is limited. When projects are large and portfolios span many regions, repeat problems can become systemic. Buyers therefore have strong incentives to ask for better evidence earlier in the process.
Anna Covert: For developers and asset owners, the takeaway is practical. Do not treat certification as the finish line. Treat it as the starting point. Ask what bill of materials was tested. Ask whether the tested product matches the product being delivered. Ask whether critical suppliers have changed. Ask what independent durability data exists and whether the testing is relevant to the project’s environmental risks. And build procurement processes that can respond when new information appears.
Alex Herrera: For manufacturers, the takeaway is just as clear. In the current market, recognized independent data is not merely a technical asset; it is a commercial one. Suppliers that can demonstrate consistency, durability, and transparency may be better positioned in procurement conversations. Those that rely only on certificates and spec sheets may face more questions, more delays, and more requests for additional testing.
Anna Covert: Ultimately, this is a sign of a maturing solar industry. As the market grows, buyers become more disciplined. They learn that quality is not a single document, and reliability is not a one-time claim. It is an evidence trail that begins with certification and continues through testing, production, shipment, installation, and long-term operation.
Alex Herrera: And that evidence trail matters because solar assets are expected to perform for decades. The industry cannot eliminate every risk, but it can improve how risks are identified, compared, and managed. In that sense, the move beyond certification is not a rejection of standards. It is an acknowledgment that standards are the floor, while long-term project success often requires a much deeper look.
Anna Covert: So when a solar buyer asks for more than a certificate, the request is not just extra paperwork. It is a response to bigger projects, tighter timelines, changing supply chains, and higher financial stakes. The question is no longer simply, “Is this module certified?” The better question is, “Do we have enough independent evidence to believe this exact product is the right fit for this exact risk profile?”
Alex Herrera: And in today’s utility-scale market, that question may define the difference between a smooth procurement process and a costly surprise in the field.
