“PID resistant,” “low LID,” “LeTID controlled” and “30-year linear warranty” are four different claims. None can be compared responsibly without the module technology, exact bill of materials, preconditioning state, electrical stress, temperature, humidity, irradiance or injection condition, duration, measurement method, sample count and acceptance rule. A nameplate wattage is a declared power at defined measurement conditions. A degradation test compares states under a stated procedure. A warranty is a contract with its own covered models, start date, power floor, measurement rules, exclusions, claim process and remedy.
The practical procurement method is to create one evidence matrix that keeps these layers separate. Request model-specific test reports for relevant degradation mechanisms; link the tested samples to the offered BOM; normalize initial and final power to a controlled measurement method; identify whether reported loss is before or after stabilization or recovery; and review the actual warranty document for the exact model and sales market. Do not convert a test certificate, cell-technology label or sales adjective into a guaranteed field-degradation rate.
This guide focuses on crystalline-silicon modules. It does not set universal pass limits, forecast lifetime energy yield or interpret a warranty on behalf of its issuer. It also does not claim any unverified SINAWATTS module technology, rating, certification, laboratory, test result, performance warranty, stock, price, MOQ, lead time or customer case.
Direct answer: what should the RFQ ask for?
For each offered module family and wattage bin, request:
- manufacturer, legal warrantor, factory/site where relevant, exact model code and revision;
- cell technology and wafer/doping description stated at a level the manufacturer can document;
- glass, encapsulant, cell, interconnect, backsheet or rear-glass and frame BOM identifiers under controlled confidentiality terms;
- nameplate Pmax, tolerance, front-side or bifacial rating basis, STC definition and flash-report format;
- stabilization or preconditioning applied before the factory nameplate measurement;
- PID test standard/edition, method/variant, polarity, voltage, temperature, humidity or surface condition, duration, UV condition, sample count and pass rule;
- LID and LeTID method, cell-level or module-level scope, irradiance/injection, temperature, dose/time, termination criteria, sample count and pass rule;
- initial, interim, final and recovered-state Pmax values with measurement uncertainty;
- laboratory identity, accreditation/scope where required, report number/date and complete result pages;
- tested model and BOM mapping to the exact production offer;
- current type-qualification evidence and retest/change-control process;
- limited product and performance-warranty documents for the destination market;
- warranty start date, beneficiary/transfer terms, degradation curve, measurement method, uncertainty treatment, exclusions, remedy and claim-cost allocation; and
- signed deviations where any requested evidence, condition or model mapping is absent.
Compare claims only after those fields are aligned. A lower reported percentage from a shorter or different stress is not automatically better. A longer warranty headline is not automatically broader coverage. A module can pass a defined qualification test without proving a precise annual field-degradation rate in every climate and system voltage configuration.
Keep PID, LID and LeTID separate
The three abbreviations describe different stress mechanisms and time histories.
Potential-induced degradation (PID) is associated with high electrical potential between the active cell circuit and grounded or conductive module surroundings, with behaviour affected by cell/module technology, polarity, electric field and environment. Different PID modes can influence current, voltage, fill factor or shunting in different ways. A PID test deliberately applies defined short-term stress; it does not reproduce every field climate or grounding configuration.
Light-induced degradation (LID) describes changes initiated by light or carrier injection, often discussed as an initial stabilization phenomenon in crystalline-silicon cells/modules. Its magnitude and kinetics depend on cell technology and treatment. A test result must state the initial condition and termination point; otherwise one supplier may report from an unstabilized state while another starts after stabilization.
Light- and elevated-temperature-induced degradation (LeTID) also involves carrier injection but is evaluated at elevated temperature and longer exposure. It can evolve and later regenerate, so a single early or late measurement may not capture the worst observed state. It is not simply “LID measured hotter.”
The 2025 IEA PVPS Task 13 report, checked on 2026-09-23, reviews LID/LeTID and PID for newer silicon cell/module technologies. It stresses that mechanisms and relevance vary with technology and discusses degradation, recovery and mitigation rather than treating the acronyms as one generic loss. Its accompanying failure fact sheets identify STC power and I-V measurements as central evidence and recommend checking warranties, BOM/cell type and test reports. These observations support due diligence; they do not create an automatic pass criterion for a quotation. IEA PVPS 2025 degradation report; IEA PVPS 2025 failure fact sheets.
Define the offered module before reviewing a claim
Start with identity. A family name can contain multiple cell formats, power bins, glass constructions, encapsulants, backsheet/rear-glass options, junction-box variants and production sites. Ask the supplier to map the report's sample designation to the sales model and controlled BOM. If the test report covers “Model ABCxxx” while the quotation offers a later suffix, require the manufacturer's scope statement or applicable retest evidence.
The BOM mapping should address components that can influence leakage paths, moisture transport, optical/electrical behaviour or thermal response. Purchasing does not need every proprietary recipe in a public document, but the manufacturer should be able to maintain a controlled internal mapping and provide change notification at a useful level. A letter saying “same technology” is weaker than a configuration table that identifies which changes are covered by the report.
IEC TS 62915:2023 addresses retesting when PV module materials or design are modified and includes updated treatment of PID-related testing in the IEC 61215 context. Ask the manufacturer to explain how its change-control system applies that logic to the tested and offered constructions. Do not infer that an old report automatically covers a new encapsulant, cell passivation stack or rear construction. IEC TS 62915:2023 official scope.
The solar module leads and connector BOM guide provides a related model-mapping method for junction leads and connectors. Apply the same discipline here: model, component, report and production revision should resolve to one controlled configuration.
Specify PID evidence by exact method and stress
The current IEC TS 62804-1:2025, checked on 2026-09-23, defines procedures for evaluating crystalline-silicon PV-module durability under short-term high-voltage stress. Its official scope describes dark methods primarily aimed at PID-shunting, UV-inclusive methods intended for PID-polarization, and a UV recovery test for PID polarization. It also says actual field durability depends on environmental conditions and module voltage relative to earth, while the tests assess sensitivity under their defined procedures. IEC TS 62804-1:2025 official scope.
That edition is materially more specific than a bare statement of “IEC 62804 tested.” Require the bidder to return:
On small screens, swipe or scroll sideways to read every column. Keyboard users can focus the table and use the arrow keys.
| PID evidence field | Required detail | Why it matters |
|---|---|---|
| Standard | Full designation, edition and method/variant | Different methods target different behaviour |
| Sample | Exact model, serials, BOM revision and quantity | Links the result to the offer |
| Pretreatment | Stabilization, conditioning and initial measurement state | Sets the comparison baseline |
| Electrical stress | Voltage magnitude, polarity and connection relative to frame/ground | Defines the electric field direction and level |
| Environment | Temperature, humidity, conductive foil/wet surface and chamber condition | Influences leakage and ionic transport |
| Optical condition | Dark or UV-inclusive, spectrum/dose where applicable | Can change observed PID mode and recovery |
| Duration | Exposure time and interruption schedule | Makes severity comparable |
| Measurements | I-V method, STC correction, EL or other diagnostics and uncertainty | Shows how loss was quantified |
| Result | Each sample before/after value, percentage change and pass rule | Prevents a favorable average hiding an outlier |
| Recovery | Whether measured, method and recovered versus stressed state | Distinguishes sensitivity and reversibility evidence |
Do not accept “zero PID” without a detection limit and complete conditions. A report may round a small measured change to zero, or its measurement uncertainty may be larger than the displayed difference. Ask for raw or unrounded Pmax results where commercially available and the laboratory's stated uncertainty.
Also distinguish qualification from project exposure. IEC 61215-2:2021 includes a test for detection of PID as MQT 21 within its terrestrial-module qualification procedures. The IEC describes the sequence as showing, as far as reasonably possible within test constraints, capability to withstand prolonged outdoor exposure; it does not present qualification as an exact lifetime prediction. IEC 61215-2:2021 official scope.
Specify LID evidence and the initial power state
IEC 63202-1:2019, checked on 2026-09-23, describes crystalline-silicon cell-level LID measurement in simulated sunlight. It determines LID magnitude by comparing maximum power at STC before and after exposure at specified temperature and irradiance. Its stated purpose is standardized cell information that helps module manufacturers manage cell mismatch and power yield. IEC 63202-1:2019 official scope.
That scope creates an important procurement boundary: a cell test is not automatically a model-level module test or warranty. Request the supplier to explain how cell results are translated into production module controls. Useful evidence includes cell-lot sampling, stabilization process, module flash timing, factory limits, traceability and change control.
Ask these questions about every “low LID” statement:
- Is the reported result from cells, mini-modules or full production modules?
- What technology and doping description applies to the tested samples?
- What was the pre-exposure state before the first Pmax measurement?
- What irradiance, spectrum, temperature and accumulated dose were applied?
- What termination/stabilization criterion ended the test?
- Was the reported loss calculated from initial, stabilized or recovered Pmax?
- How many samples and production lots were tested?
- What maximum individual result and uncertainty accompanied the average?
- Does the factory nameplate flash occur before or after the claimed stabilization step?
- Which warranty-year boundary, if any, expressly accounts for initial degradation?
Do not add a test loss mechanically to a nameplate value without understanding the nameplate state. A manufacturer may bin modules after a stabilization treatment; another may characterize initial power differently. The correct comparison is declared power plus documented measurement/stabilization process, not an assumed universal sequence.
Specify LeTID evidence across degradation and recovery
IEC TS 63202-4:2022, checked on 2026-09-23, describes cell-level measurement of LeTID in crystalline-silicon cells under simulated sunlight. Its official scope contrasts the moderate-temperature, initial-duration LID evaluation in IEC 63202-1 with elevated-temperature and longer-duration exposure used to evaluate LeTID behaviour and mitigation. IEC TS 63202-4:2022 official scope.
For procurement, request a time-series rather than only “before” and “after” if the method and laboratory generate it. The lowest recorded power state can matter more than the final point if degradation is followed by regeneration. Ask the report to identify:
- test type and whether cell, mini-module or full module;
- specimen technology and production/BOM mapping;
- initial conditioning and measurement state;
- carrier-injection method, irradiance or current condition;
- specimen temperature and how it was controlled/measured;
- exposure duration or dose and measurement intervals;
- termination criteria for degradation and any recovery stage;
- Pmax, Isc, Voc and fill-factor development where reported;
- individual-sample results, not only group average; and
- the manufacturer's production mitigation and ongoing monitoring control.
Do not assume a cell-level LeTID result alone establishes full-module behaviour. Cell interconnection, thermal distribution, encapsulation and module measurement add other boundaries. Conversely, do not dismiss cell-level evidence: it can be valuable for controlling the underlying cell process when it is mapped to the actual production lot and supported by module-level qualification or verification appropriate to the purchase.
Separate nameplate power from degradation-test loss
A module nameplate Pmax is a declared electrical rating under specified conditions. It is not the real-time power expected on a roof under arbitrary irradiance, cell temperature, spectrum, angle, soiling or wiring loss. The STC, NMOT and datasheet output guide explains those boundaries in detail.
IEC 60904-1:2020, checked on 2026-09-23, describes I-V measurement procedures for PV cells, subassemblies and modules in natural or simulated sunlight. IEC TR 60904-14:2020 gives guidance for production-line Pmax measurements and reporting at STC, including common complications and uncertainty sources. These measurement documents are the appropriate reference layer for comparing power values; they do not themselves define a commercial warranty remedy. IEC 60904-1:2020 official scope; IEC TR 60904-14:2020 official scope.
Request factory flash data with serial number, test date, measured Pmax, Voc, Isc, Vmp, Imp, test condition, reference-device traceability and stated tolerance or uncertainty policy. Determine whether data are measured, rounded, binned or copied from the datasheet. The flash-test, EL and traceability guide provides a complete receiving record.
When comparing a degradation percentage, confirm the denominator. Suppliers may calculate change from initial measured Pmax, stabilized Pmax, nameplate Pmax or another baseline. Require the equation in the report, for example:
reported change (%) = 100 × (Pmax after stress − Pmax before stress) / Pmax before stress.
That expression shows arithmetic only. The test standard and report control which states and corrections belong in the calculation.
Use measurement uncertainty before declaring pass or fail
Small differences can be difficult to resolve when measurement uncertainty is similar in magnitude. Ask the laboratory for its reported expanded uncertainty, coverage statement, calibration traceability and method of comparing before/after values. Do not subtract an assumed tolerance from one bidder and ignore it for another.
Consider a bounded hypothetical example. A module has a fictional 600 W nameplate and a fictional contractual first-year floor of 99%, which would be 594 W if that simple formula and model scope apply. An accepted laboratory reports 589 W at STC with a fictional expanded uncertainty of ±1.5% of the reading, about ±8.8 W. The uncertainty interval overlaps 594 W. This arithmetic does not decide the claim. The actual warranty's measurement, uncertainty and dispute provisions must be followed, and other causes such as mismatch, damage or calibration status must be investigated.
For a fictional PID comparison, suppose three samples change by −1.1%, −1.4% and −3.8% under one fully defined method. Reporting only the average, −2.1%, conceals the outlier. Whether any result passes depends on the issued acceptance rule and how uncertainty is handled. The example supports requesting individual data; it is not a universal PID limit.
Read the power warranty as a contract
A product warranty and a performance warranty usually address different obligations. Review the exact document incorporated into the purchase contract, not a website icon. Map at least these fields:
On small screens, swipe or scroll sideways to read every column. Keyboard users can focus the table and use the arrow keys.
| Warranty field | Procurement question |
|---|---|
| Warrantor and territory | Which legal entity stands behind the document for the destination market? |
| Covered models | Does the exact full model code and construction appear? |
| Start date | Shipment, delivery, installation, invoice or another defined event? |
| Beneficiary/transfer | Who may claim, and what transfer records are required? |
| Power curve | What first-period floor and later decline formula are actually written? |
| Rated surface | For bifacial modules, front side only or another stated basis? |
| Measurement | Which conditions, standard, lab and uncertainty treatment apply? |
| Causation | Must loss be attributable to material/workmanship or another defined cause? |
| Exclusions | Installation, system voltage, environment, handling, alteration and maintenance conditions? |
| Notice/evidence | Deadline, serials, invoices, data, photographs and test records? |
| Remedy | Repair, replacement, added modules, refund or another option, and who chooses? |
| Costs | Removal, freight, customs, access, retest and reinstallation responsibility? |
LONGi's distributed-generation limited warranty available on its official domain and checked on 2026-09-23 illustrates why the underlying document matters. It lists specific covered model families with different performance curves, states a front-side-only boundary for certain bifacial-module performance warranties, defines STC measurement and consideration of measurement tolerance under IEC 60904, and specifies claim information and remedies. Those terms belong to the listed LONGi models and document; they are not SINAWATTS terms and should not be copied into another offer. LONGi distributed-generation module limited warranty.
An RFQ should request the supplier's actual warranty and deviations. Do not ask a bidder merely to confirm “30 years.” Two 30-year documents can differ in the first-year floor, annual formula, covered power surface, proof, exclusions, remedy and claimant costs.
Connect laboratory evidence to field conditions without overclaiming
Accelerated tests help compare sensitivity under controlled stress. They are not literal time machines. Field PID depends on system voltage relative to ground, polarity, climate, wetness/soiling, construction and operation. Field LID/LeTID depends on cell technology, temperature and exposure history. Energy yield also includes irradiance, thermal losses, soiling, mismatch, availability, wiring, inverter behaviour and shading.
The current IEA PVPS report notes that degradation modes evolve with newer cell architectures and that laboratory-to-field interpretation remains technology-specific. Use the test report as one risk-control input together with project voltage architecture, climate, manufacturer instructions and contractual allocation. Do not translate “2% after a test” into “2% over 25 years” unless a qualified model and contract explicitly support that conclusion.
At design review, document maximum system voltage, grounding/earthing concept, inverter topology where relevant, module position in strings and environmental exposure. Ask the module and inverter/system parties to state compatibility within their respective scopes. A proposal to use external recovery or mitigation hardware should include responsible engineering review, operating constraints and warranty acceptance; it is not a substitute for a suitable module specification.
Build a supplier comparison matrix
Use one row for every claim and keep “provided,” “applicable” and “passes” separate.
On small screens, swipe or scroll sideways to read every column. Keyboard users can focus the table and use the arrow keys.
| Claim | Evidence required | Hold condition |
|---|---|---|
| PID resistance | IEC TS 62804-1 edition/method, exact stress, samples, individual loss, uncertainty and BOM mapping | Method, polarity, model or result missing |
| Low LID | IEC 63202-1 cell report or applicable module evidence, stabilization state and production control | Baseline or cell-to-module mapping unclear |
| LeTID control | IEC TS 63202-4 or stated applicable method, temperature/injection/time series, mitigation and sample mapping | Only a final regenerated point or marketing letter supplied |
| Nameplate power | Model datasheet, power tolerance and serial flash-report method | Factory measurement state or traceability unknown |
| Type qualification | Complete report/certificate scope and exact model/BOM mapping | Certificate family does not resolve to offered construction |
| Performance warranty | Full market-specific contract and model list | Headline supplied without operative terms |
| Field forecast | Named energy model, climate inputs and degradation assumptions | Test percentage presented as annual field rate without basis |
Score evidence completeness separately from the numerical result. A supplier with a modest but transparent, applicable result can be lower risk than one offering “zero degradation” without test conditions or sample identity.
Plan receiving and project baseline records
At receiving, verify pallet and module labels, model codes, serial ranges, quantities, visible damage and document revision. Preserve factory flash data and agreed sampling records. Storage and handling can create other damage that must not be mislabeled as PID or LID; use the solar panel packaging and pallet-storage guide to control that boundary.
If independent baseline testing is required, agree the laboratory, samples, conditioning, transport, measurement standard, uncertainty and witness rights before shipment. Random sampling should follow the contractual plan rather than selecting only a visibly perfect module. Record seal numbers and chain of custody.
EL images can support diagnostics but do not independently quantify warranted Pmax. I-V data can reveal changes, yet the causal attribution may require further analysis. Junction-box or bypass-diode faults, cracked cells, connector issues, shading and measurement error can affect power differently. The junction-box and bypass-diode guide covers that separate evidence set.
For operation, preserve commissioning I-V or module sample results, string configuration, inverter settings, weather/irradiance data and maintenance history. A warranty claim is easier to evaluate when serial identity and baseline evidence survive handover. Monitoring underperformance alone does not diagnose PID, LID or LeTID.
Control changes after award
Require advance notice for changes to cell technology or supplier, wafer/doping specification, passivation stack, encapsulant, glass, backsheet/rear glass, interconnect, frame, junction box, factory or stabilization process when those changes can affect accepted evidence. The manufacturer should state whether the change remains within the qualified family and what retest or engineering review supports that conclusion.
Do not treat an increased wattage bin as automatically identical. It may be a binning extension of the same construction, or it may accompany cell/process changes. Ask for the model-mapping statement and updated report scope.
Maintain a document index with report number, issue date, model scope, BOM revision, laboratory, standard/edition and supersession status. At production release, verify that no evidence expired or was replaced and that the warranty version in the contract remains accessible.
Send a complete PV degradation-evidence RFQ
Provide the project location, climate/design inputs, system voltage and grounding concept, module quantity, target model class, bifacial/monofacial configuration, acceptance needs and warranty jurisdiction. Ask each bidder for exact model/BOM identity; nameplate and flash-measurement basis; PID, LID and LeTID reports with conditions and individual results; qualification/change-control evidence; market-specific warranties; and a signed exception list. Require supplier-specific confirmation of price, availability, production capacity, MOQ, delivery, certification scope and warranty enforceability. This guide makes no such promise for SINAWATTS or any cited organization.
Send a solar panel evidence RFQ
Buyer FAQ
Does “IEC 61215 certified” prove zero PID, LID and LeTID for 30 years?
No. IEC 61215-2 defines qualification test procedures, including a PID detection test in the 2021 edition, within stated constraints. Qualification is not a zero-degradation guarantee or an exact field-life forecast. Review the full report scope, separate mechanism-specific evidence and actual warranty contract.
Is PID the same as normal annual degradation?
No. PID is associated with electrical potential stress and technology/environment conditions. A commercial warranty curve may aggregate contractual power expectations without identifying one physical mechanism. Keep PID test evidence, field diagnosis and warranty-floor calculation separate.
Can a cell-level LID or LeTID report qualify a complete module?
It is useful process evidence but does not by itself establish every full-module behaviour or warranty. Require mapping from tested cells to production lots, the manufacturer's module stabilization and quality controls, applicable module-level evidence, and change control for the offered BOM.
Should we compare only the final LeTID measurement?
Not necessarily. Degradation and regeneration can occur during exposure, so the final point may not be the lowest power state. Request the time series, termination rule, worst observed value and recovery-stage identification under the stated method.
Does a 600 W nameplate mean the module produces 600 W on the roof?
The nameplate refers to defined rating conditions and measurement practice. Field output changes with irradiance, cell temperature, spectrum, angle, soiling, wiring, mismatch and system operation. Use the nameplate and flash data for controlled comparison, then model project energy with appropriate inputs.
Can a brochure's “30-year warranty” be used as the degradation acceptance criterion?
Only after reviewing the operative warranty and incorporating the agreed requirement into the contract. Confirm the model, warrantor, start date, power formula, rated surface, measurement and uncertainty rules, exclusions, evidence, remedy and costs. The headline alone is incomplete.
What should happen if the laboratory result is close to the warranty floor?
Follow the warranty and purchase-contract rules for accepted laboratory, conditioning, measurement standard, uncertainty and dispute testing. Do not declare pass or fail from a rounded number while ignoring uncertainty. Preserve samples, serial identity and chain of custody.
Does a PID recovery result erase the original degradation result?
No. Report stressed and recovered states separately. Recovery evidence can help characterize a mechanism, but purchasing still needs the specified stressed-state acceptance, field relevance and contractual treatment. Do not replace an adverse result with only the recovered endpoint.
What is the minimum defensible supplier package?
Obtain exact model/BOM mapping, current datasheet, serial flash-data format, applicable qualification documents, full PID method/report, LID and LeTID evidence appropriate to the technology, measurement uncertainty, change-control statement, market-specific product/performance warranties and a signed deviation list. Missing conditions should remain open items rather than being filled with assumptions.