TECHNOLOGY EXPLAINER
Outdoor Testing and Durability Assessment
— passing a test is not a lifetime guarantee
IEC 61215, the international standard for PV modules, says in its own scope that test results are not to be construed as a quantitative prediction of module lifetime. On top of that, perovskites show effects that silicon does not, such as "reversible degradation", where performance recovers overnight. This article sorts out IEC 61215, the ISOS protocols, and the difference between accelerated testing and outdoor trials, from a materials engineer's point of view.
- What durability assessment is, in three points
- Three yardsticks: IEC 61215, ISOS and outdoor trials
- IEC 61215: design qualification, not a lifetime forecast
- A materials engineer's view (1): tests built for silicon look for the ways silicon fails
- The ISOS protocols: common procedures for comparing results between labs
- A materials engineer's view (2): degradation that recovers at night, and how to assess reversibility
- Linking accelerated tests to outdoor exposure: the example of UV
- Our calculation: how many outdoor years a test's light dose represents
- Reports from outdoor trials
- A materials engineer's view (3): the material sets the acceleration factor
- Open problems, and what this article could not confirm
- Glossary / References / Claim-to-source audit
Sourced = stated in published material, a peer-reviewed paper or the public summary of a standard (link given)
Our calculation = a value this article derived from assumptions it states
Not yet confirmed = a plan, target or outlook with no confirmed track record
Structural readings and interpretations for materials and evaluation are marked separately as Commentary.
Because the full texts of the standards are paid, this article limits itself to the titles and scope descriptions published on the IEC webstore, and to what peer-reviewed papers citing them say.
1. What durability assessment is, in three points
- The lifetime expected: the ISOS consensus statement (Khenkin et al., Nature Energy 2020) puts the expected lifetime of utility-scale modules at 20 to 25 years, a figure set by the reliability of silicon-wafer modulesSourced
- How it is checked: three approaches are used: product qualification tests (such as IEC 61215), procedures for comparing results between laboratories (ISOS), and real outdoor trials
- What makes perovskites difficult: the same statement says that existing qualification tests such as IEC 61215 were designed to screen for the well-understood degradation modes of silicon panels, and are likely to be poorly suited to perovskites, whose materials and device structures are fundamentally differentSourced
"So many hours" in an accelerated test and "so many years" outdoors can be linked only through material-specific assumptions. IEC 61215-1:2021 says in its scope that the actual service life of qualified modules depends on their design, environment and operating conditions, and that test results are not to be construed as a quantitative prediction of module lifetimeSourced.
2. Three yardsticks: IEC 61215, ISOS and outdoor trials
3. IEC 61215: design qualification, not a lifetime forecast
| Standard | Scope as described on the IEC webstore (summary) |
|---|---|
| IEC 61215-1:2021 (test requirements) | Requirements for the design qualification of terrestrial PV modules suitable for long-term operation in outdoor climates. The service life of qualified modules depends on design, environment and operating conditions, and test results are not to be construed as a quantitative prediction of lifetime. Covers all terrestrial flat-plate modules, including crystalline silicon and thin film. Does not apply to modules not intended for long-term use, such as flexible modules fitted to awnings or tents. The second edition added testing of flexible modules (the bending test, MQT 22) and the treatment of bifacial modules |
| IEC 61215-2:2021 (test procedures) | The purpose of the tests is to determine the electrical characteristics of the module and to show, as far as possible within reasonable constraints of cost and time, that it can withstand prolonged outdoor exposure. The second edition added the dynamic mechanical load test (MQT 20), a test for detecting potential-induced degradation (MQT 21) and the bending test (MQT 22), and revised the hot-spot test procedure for monolithically integrated thin-film modules |
All Sourced (IEC webstore [References 2 and 3]). Because the full texts of the standards are paid, detailed test conditions have not been checked against the text.
Typical test conditions can be read from peer-reviewed papers that cite the standard. Mariani et al. (2024) describe IEC 61215's damp heat test as at least 1,000 hours at 85 °C and 85% relative humidity, and its thermal cycling test as at least 200 cycles between −40 °C and 85 °C, both with more than 80% efficiency retention as the benchmark, and also mention the humidity-freeze testSourced. Zhang et al. (2025), who ran an outdoor trial, point out that the light dose specified by IEC 61215 is only 15 kWh/m², far less than the cumulative dose received in real operationSourced.
4. A materials engineer's view (1): tests built for silicon look for the ways silicon fails
The Khenkin consensus statement says existing qualification tests such as IEC 61215 were designed, with the outdoor performance of silicon panels in mind, to screen for "well-understood degradation modes" tied to module-level problems, and are likely to be unsuitable for perovskites and similar devices because their material properties and device structures are fundamentally differentSourced. The statement also says that various reports have shown existing procedures to be insufficient for assessing the stability of these devicesSourced.
Effects described as specific to perovskites include the following (according to the same statement)Sourced.
- Light-induced migration of ions and defects, and phase segregation (accelerated in the light-soaking tests, ISOS-L)
- Decomposition under ultraviolet light, and increased non-radiative recombination in structures using mesoporous TiO2
- Ion redistribution driven by electric fields (a new dark-bias test, ISOS-V, is proposed)
- Degradation that fully or partly recovers in the dark (a new light-dark cycling test, ISOS-LC, is proposed)
- Phase transitions within the operating temperature range in compositions such as MAPbI3
A qualification test is a net for efficiently catching the ways past products have failed. If the mesh is sized for the ways silicon fails, a different material's failure modes may slip through, or it may fail excessively under conditions that are harmless for silicon. Rather than assessing a new material with qualification tests alone, you need to identify the degradation mechanisms from the materials side and design acceleration conditions to match (our commentary).
5. The ISOS protocols: common procedures for comparing results between labs
The ISOS protocols are test procedures agreed at the International Summit on Organic Photovoltaic Stability (ISOS) held in Roskilde, Denmark, in 2010, and published for organic photovoltaics in 2011. The 2020 consensus statement by Khenkin et al. extended them to perovskitesSourced.
- No pass or fail: unlike IEC qualification tests, cells neither "pass" nor "fail" ISOS tests. They are aimed mainly at lab-scale devices, to make test results from different laboratories comparableSourced
- Not a substitute for qualification tests: they are not intended to replace existing qualification standards; the aim is to harmonise stability assessment and to understand failure modesSourced
- Three levels: each test family has basic (level 1), intermediate (level 2) and advanced (level 3) versions. Level 1 can be done with common equipment but controls the stress factors only loosely, and is described as the minimum requirement. Levels 2 and 3 need environmental chambers and maximum power point tracking (MPPT) equipmentSourced
| Test family | Stress | Main conditions (from the tables in the consensus statement) |
|---|---|---|
| ISOS-D (dark storage) | Atmosphere, temperature, humidity | D-1: ambient room air. D-2: 65 or 85 °C. D-3: 65 or 85 °C at 85% relative humidity (damp heat) |
| ISOS-V (bias in the dark) | Electrical bias | Voltage applied in the dark to study degradation from ion migration (newly proposed for perovskites) |
| ISOS-L (light soaking) | Light, temperature, humidity | L-1: simulated sunlight in ambient air at room temperature. L-2: 65 or 85 °C. L-3: 65 or 85 °C, about 50% relative humidity, held at MPP |
| ISOS-O (outdoor) | Natural sunlight and weather | O-1: measured periodically under simulated sunlight. O-2: measured under natural light. O-3: MPP tracking in situ under natural light, with periodic measurements under simulated sunlight as well |
| ISOS-T (thermal cycling) | Temperature changes | T-3: −40 to +85 °C (relative humidity below 55%) |
| ISOS-LC (light-dark cycling) | Light switched on and off | Periods of 2, 8 or 24 hours, with light-to-dark ratios of 1:1 or 1:2. The 24-hour period (such as 12 hours light, 12 hours dark) mimics the daily cycle |
All Sourced (Khenkin et al. 2020 [Reference 1]). A family of tests under inert atmosphere (ISOS-I), to study intrinsic stability without the influence of encapsulation, is also proposed.
The statement also provides a checklist to make reports more reproducible. For J-V measurements, for example, it asks authors to report the type, intensity, spectrum, filters and calibration of the light source, scan rate and direction, dwell times and preconditioning; for MPPT, the hardware, tracking algorithm, delay time and tracking duration; and for EQE, a comparison of the calculated Jsc with the Jsc from J-VSourced. Measurement methods themselves were covered in our explainer on conversion efficiency and performance metrics.
6. A materials engineer's view (2): degradation that recovers at night, and how to assess reversibility
The Khenkin consensus statement says it has been repeatedly shown that various perovskite degradation modes fully or partly reverse in the dark (metastability), so tests that alternate light and dark apply a very different stress from continuous illuminationSourced.
- Two kinds of behaviour have been reported: efficiency that rises in light and falls in the dark, and degradation under light that recovers in the darkSourced
- Reversible performance loss is attributed to cation redistribution, the formation of metastable defects, and reversible chemical reactionsSourced
- In cells that decline in the dark and recover in light, "fatigue", with recovery slowing over successive light-dark cycles, has also been reportedSourced
- It is therefore recommended to track recovery by keeping devices in the dark after testing, and to describe precisely the load and recovery time before J-V measurementSourced
For engineers used to reliability testing of materials, this means the amount of degradation depends on whether you measure right after the test or after leaving it overnight. Outdoors, every day is a light-dark cycle, so how much night-time recovery offsets daytime degradation shapes energy yield over the years. Put another way, an accelerated test under continuous light gives no chance to recover, so it can be both too harsh and blind to degradation that does not recover (our commentary).
7. Linking accelerated tests to outdoor exposure: the example of UV
The Khenkin consensus statement says that although outdoor test (ISOS-O) conditions depend on weather, location and season and cannot be reproduced, their results are the most relevant to real operation and can be used directly for realistic lifetime assessment in a given climate. It adds that outdoor testing checks whether the list of failure modes found in the lab is complete, and serves as the reference point for the "acceleration factor" linking outdoor lifetime with lifetime under accelerated conditions, noting that for silicon modules this approach helped establish IEC 61215Sourced.
An example of trying this approach on perovskites is Zhang et al. (2025, Nanoscale Advances), by researchers from Microquanta Semiconductor of Hangzhou, China Three Gorges Corporation and China Huadian Corporation. They split sub-modules from the same production batch between outdoor exposure and a UV accelerated-test chamber and compared themSourced.
| Item | What the paper states |
|---|---|
| Outdoor installation | In April 2021, a small power plant of 20 sub-modules of 30 cm × 40 cm (about 13 W each, about 260 W in total) was installed in Quzhou, Zhejiang Province, China (humid subtropical). FA0.9Cs0.1PbI3-based, inverted (p-i-n) structure. Fixed racking tilted at 20° |
| Three years outdoors | In continuous operation from April 2021 to March 2024, the average loss in conversion efficiency was 2.83%. The annual average performance ratio (PR) went 102.10% → 101.90% → 101.30% (a 0.78% decline over three years). The first-year outdoor efficiency loss was 1.6% |
| Accelerated test | A light source boosting blue-violet light at 390 to 455 nm in addition to ultraviolet (UVA and UVB) applied a UV dose of 60 kWh/m² at 65 °C (14 days), with 96.86% efficiency retention (a 3.14% loss). The authors say this reproduces about two years of outdoor degradation |
| Estimating the UV dose | This UV band of the AM1.5G spectrum is about 38.8 W/m² (about 4.5% of the total). With 1,200 to 1,600 equivalent sun hours a year in Quzhou, the annual UV dose was estimated at about 47 to 60 kWh/m² |
| Checking the encapsulation | Modules of the same design went through 3,000 hours of damp heat at 85 °C and 85% RH with only a slight efficiency loss, leading to the conclusion that degradation stemmed from the materials and photophysical processes rather than moisture ingress |
| Relation to standards | The authors say the results support a perovskite-specific reliability testing framework and the international standard under development, IEC TS 63624-1 |
All Sourced (Zhang et al. 2025 [Reference 5]). The PR values above 100% follow the paper's definition (actual output relative to output at STC). The content of IEC TS 63624-1 could not be confirmed from public information on the standard for this article.
8. Our calculation: how many outdoor years a test's light dose represents
Assumptions (all using figures from the Zhang paper)Our calculation
- Irradiance in the relevant UV band of AM1.5G of 38.8 W/m², and 1,200 to 1,600 equivalent sun hours a year
- Annual UV dose = 38.8 W/m² × 1,200 to 1,600 h = about 47 to 62 kWh/m² (almost the same as the paper's estimate of about 47 to 60)
| Test UV dose | Simple conversion to outdoor years | Time taken |
|---|---|---|
| 15 kWh/m² (cited in the paper as the IEC 61215 dose) | about 0.24 to 0.32 years | — |
| 60 kWh/m² (the paper's accelerated test) | about 1.0 to 1.3 years | 14 days (65 °C) |
| 180 kWh/m² (a further dose shown in the paper) | about 2.9 to 3.9 years | — |
- Time compression: applying 60 kWh/m² in 14 days compresses about 1.0 to 1.3 years outdoors, in UV dose alone, into 14 days: an acceleration of about 25 to 34 times
- Outdoor degradation rate: treating the 2.83% loss over three years as a constant rate gives about 0.94% a year
How to read it: the paper's abstract says 60 kWh/m² reproduces "about two years" of outdoor degradation, whereas a simple conversion by UV dose alone gives about 1.0 to 1.3 years. The body of the paper explains the larger loss in the accelerated test (3.14%) compared with the first year outdoors (1.6%) by "the increased UV dose and the higher test temperature"Sourced. In other words, a conversion into "so many years" depends on assumptions not only about UV dose but about how temperature and blue-violet intensity act.
Assumptions and limits: the simple conversion assumes UV dose determines degradation, and leaves out temperature, humidity, light-dark cycling and visible light. The calculation does not refute the paper's conclusion; it is meant to make the assumptions behind the conversion visible.
9. Reports from outdoor trials
At the time of the Khenkin consensus statement (2020), studies of perovskite outdoor stability were described as still few. Even so, it says they had yielded insights such as the importance of light-dark cycling and unexpectedly high open-circuit voltage at low irradianceSourced. Since then, reports such as the following have appeared.
| Report | Devices and location | Duration and results |
|---|---|---|
| Zhang et al. 2025 | 20 sub-modules of 30 × 40 cm (about 260 W), Quzhou, Zhejiang Province, China | Average efficiency loss of 2.83% over three years; annual average PR from 102.10% to 101.30% |
| Yang et al. 2026 (Nature) | A module, in real-time outdoor field testing | Retained 85.8% of initial module efficiency after 258 days |
| Nikbakht et al. 2025 | A 0.73 m² panel of connected 156 cm² modules, at a test site on Crete, Greece | Up to 12.0% efficiency under outdoor conditions. Evaluated by outdoor MPPT |
All Sourced ([References 5, 6 and 7]). Structure, encapsulation, climate, duration and evaluation method all differ, so these figures cannot be compared with one another.
Assumption: degradation proceeds at a constant rate, annualisedOur calculation
- Zhang et al.: 2.83% over three years → about 0.94% a year
- Yang et al.: 14.2% (100 − 85.8) over 258 days → 14.2 × 365 ÷ 258 = about 20% a year
Both are "outdoor trials", yet the annualised degradation rates differ by a factor of more than 20. Assumptions and limits: degradation does not necessarily proceed at a constant rate (it may be fast at first and slow later, for example), and structure, encapsulation, climate and evaluation definitions also differ. The calculation is meant to show that the figures from a single outdoor report cannot be generalised as "the lifetime of perovskites".
10. A materials engineer's view (3): the material sets the acceleration factor
What stands out in the Zhang accelerated test is that it adds not only ultraviolet (UVA and UVB) but also blue-violet light at 390 to 455 nm, at about four times the intensity of AM1.5G. The authors say including this high-energy band matters because it accelerates degradation through mechanisms such as trap-state formation and ion migrationSourced.
In weathering tests of polymers, too, it is known that which wavelength range does the damage (the action spectrum) differs from material to material, and that a light source that does not match it fails to correlate with outdoor results. The same applies to perovskites: rather than "so many hours under the standard's light source", you need to determine from the materials side "how many times faster than outdoors, at the wavelengths and temperatures that break this material" (our commentary).
Another lesson is that the same paper separately confirmed the soundness of the encapsulation with 3,000 hours of damp heat, separating light-induced degradation from degradation caused by moisture ingressSourced. When you intensify one stress in an accelerated test, confirm with another test that no other failure mode has crept in: a basic principle of materials evaluation under combined degradation applies here too (our commentary). Encapsulation was covered in our explainer on encapsulation and barrier layers.
11. Open problems, and what this article could not confirm
(1) A perovskite-specific standard
Zhang et al. mention IEC TS 63624-1 as an international standard under developmentSourced, but this article's research could not confirm its title, scope or publication status from official public information such as the IEC webstore, so its content is not describedNot yet confirmed.
(2) There is no 20-to-25-year track record yet
Against the expected lifetime of 20 to 25 years cited by Khenkin et al., the longest outdoor trial this article could confirm is three years (Zhang et al.)Sourced. Given the history of the technology, a 20-year-plus outdoor record cannot yet exist. Long-term lifetime still has to be estimated from accelerated tests and degradation modelsNot yet confirmed. The effect on the cost of electricity is covered in our explainer on the levelized cost of electricity.
(3) Companies' durability claims
Many durability figures that companies present as "equivalent to so many years" are conversions from accelerated tests. Read them by checking whether the test conditions used for the conversion (light, temperature, humidity, cycling) and the basis for mapping them to outdoor exposure have been published (our commentary).
- IEC 61215 is design qualification; its test results are not a quantitative lifetime forecastSourced
- Existing qualification tests look for the well-understood degradation modes of silicon, and are said to be likely poorly suited to perovskitesSourced
- ISOS is a set of common procedures with no pass or fail, with test families for dark storage, bias, light, outdoor, thermal cycling and light-dark cycling, at three levelsSourced
- Perovskites show degradation that recovers at night, so light-dark cycling is a different stress from continuous illuminationSourced
- Converted by UV dose alone, 60 kWh/m² is about 1.0 to 1.3 years outdoors. "So many years" depends on the assumptionsOur calculation
- Annualised, outdoor degradation rates differ by a factor of more than 20 between reportsOur calculation
12. Glossary
- IEC 61215
- The international standard for design qualification and type approval of terrestrial PV modules. Part 1 sets test requirements, Part 2 test procedures.
- Design qualification (type approval)
- Confirming that modules of a given design withstand a defined sequence of tests.
- ISOS protocols
- Common procedures for stability testing that began with organic solar cells and were extended to perovskites. There is no pass or fail.
- Damp heat test
- An accelerated test holding devices at high temperature and humidity (for example 85 °C and 85% RH) for a long time.
- Thermal cycling test
- A test alternating between low and high temperatures (for example −40 °C and 85 °C) to reveal damage from differences in thermal expansion.
- Light-dark cycling (ISOS-LC)
- A test that switches light on and off repeatedly to study degradation and recovery.
- Metastability (reversible degradation)
- Performance that changes under light or voltage and fully or partly returns when conditions are restored.
- Acceleration factor
- A factor expressing how many times longer in the real service environment an accelerated test period corresponds to.
- Performance ratio (PR)
- Actual energy generated divided by the theoretical yield estimated from output at STC and irradiation.
- Equivalent sun hours
- Irradiation converted into hours of "1 sun" at 1,000 W/m².
- MPPT
- Maximum power point tracking: continually adjusting the load to keep operating at the maximum power point.
- Action spectrum
- How much a reaction such as degradation occurs under light of each wavelength.
13. References (primary sources)
- Khenkin MV, Katz EA, Abate A et al. “Consensus statement for stability assessment and reporting for perovskite photovoltaics based on ISOS procedures”, Nature Energy 5, 35–49 (2020) (publisher PDF) https://www.nature.com/articles/s41560-019-0529-5.pdf
- IEC “IEC 61215-1:2021 Terrestrial photovoltaic (PV) modules - Design qualification and type approval - Part 1: Test requirements”, IEC webstore https://webstore.iec.ch/en/publication/61345
- IEC “IEC 61215-2:2021 Terrestrial photovoltaic (PV) modules - Design qualification and type approval - Part 2: Test procedures”, IEC webstore https://webstore.iec.ch/en/publication/61350
- Mariani P et al. “Low-temperature strain-free encapsulation for perovskite solar cells and modules passing multifaceted accelerated ageing tests”, Nature Communications 15, 4552 (2024) (full text on PMC) https://pmc.ncbi.nlm.nih.gov/articles/PMC11137052/
- Zhang L, Liu D, Du G et al. (Microquanta, China Three Gorges Corporation, China Huadian Corporation) “Report on the relevance of perovskite module outdoor ageing performance and indoor UV degradation trend”, Nanoscale Advances 7, 6248–6256 (2025) (full text on PMC) https://pmc.ncbi.nlm.nih.gov/articles/PMC12380093/
- Yang T, Zhao E, Wu N et al. “Stereoelectronic manipulation of ligands for perovskite solar cells”, Nature 654, 660–667 (2026) (full text on PMC) https://pmc.ncbi.nlm.nih.gov/articles/PMC13275290/
- Nikbakht H et al. “Upscaling Perovskite Photovoltaics: from 156 cm² Modules to 0.73 m² Panels”, Advanced Science 12, 2416316 (2025) (full text on PMC) https://pmc.ncbi.nlm.nih.gov/articles/PMC12165116/
14. Claim-to-source audit
| Claim in the text | Basis | Label |
|---|---|---|
| That the expected lifetime of utility-scale modules is 20 to 25 years, set by silicon. That existing qualification tests (such as IEC 61215) screen for the well-understood degradation modes of silicon and are likely unsuitable for perovskites and similar devices, and that reports show existing procedures are insufficient. That ISOS was agreed at the 2010 summit in Roskilde and published in 2011, and extended to perovskites in 2020. That there is no pass or fail and the aim is comparison between labs, and that it is not a replacement for qualification standards. The three levels, with level 1 as the minimum requirement. The content and conditions of ISOS-D, V, L, O, T, LC and I. Light-induced ion and defect migration and phase segregation; UV decomposition and non-radiative recombination in TiO2 structures; field-driven ion redistribution; phase transitions; the difference between dry and humid conditions. The two kinds of reversible behaviour, their causes, fatigue, and the recommendations to track recovery and describe load and recovery time. That outdoor testing is not reproducible but most relevant to real operation, checks failure modes, anchors acceleration factors and helped establish IEC 61215 for silicon. That outdoor studies were few as of 2020, with the importance of light-dark cycling and high Voc at low irradiance known. The reporting checklist | Reference 1 https://www.nature.com/articles/s41560-019-0529-5.pdf | Sourced |
| The scope of IEC 61215-1:2021 (design qualification of modules suitable for long-term operation; that lifetime depends on design, environment and operating conditions and test results are not to be construed as a quantitative lifetime prediction; applicability and exclusions; the addition of the bending test MQT 22 and bifacial modules in the second edition) | Reference 2 https://webstore.iec.ch/en/publication/61345 | Sourced |
| The purpose of IEC 61215-2:2021 (showing, within constraints of cost and time, that modules withstand prolonged outdoor exposure), the addition of MQT 20, 21 and 22, and the revision of the hot-spot test for monolithically integrated thin film | Reference 3 https://webstore.iec.ch/en/publication/61350 | Sourced |
| IEC 61215 damp heat (85 °C, 85% RH, at least 1,000 hours) and thermal cycling (−40 to 85 °C, at least 200 cycles), the benchmark of over 80% efficiency retention, and mention of the humidity-freeze test | Reference 4 https://pmc.ncbi.nlm.nih.gov/articles/PMC11137052/ | Sourced |
| The authors' affiliations (Microquanta, China Three Gorges Corporation, China Huadian Corporation). The 20 sub-modules in Quzhou (30 × 40 cm, about 13 W each, about 260 W in total), FA0.9Cs0.1PbI3-based p-i-n, 20° tilt. An average efficiency loss of 2.83% over three years; annual average PR of 102.10, 101.90 and 101.30% (a 0.78% decline); 1.6% in the first year. The light source including blue-violet light (390 to 455 nm, about four times AM1.5G); 96.86% retention at 65 °C, 60 kWh/m² and 14 days; the abstract's "about two years". 38.8 W/m² (about 4.5%) and 1,200 to 1,600 hours a year giving 47 to 60 kWh/m² a year. The conclusion from 3,000 hours of damp heat that degradation came from materials and photophysical processes. The point that the IEC 61215 dose of 15 kWh/m² is less than in real operation. The mention of IEC TS 63624-1. The explanation that trap formation and ion migration accelerate degradation | Reference 5 https://pmc.ncbi.nlm.nih.gov/articles/PMC12380093/ | Sourced |
| That a module retained 85.8% of its initial efficiency in 258 days of real-time outdoor testing | Reference 6 https://pmc.ncbi.nlm.nih.gov/articles/PMC13275290/ | Sourced |
| That the 0.73 m² panel reached up to 12.0% under outdoor conditions at the test site on Crete, evaluated by outdoor MPPT | Reference 7 https://pmc.ncbi.nlm.nih.gov/articles/PMC12165116/ | Sourced |
| Annual UV dose of 38.8 × 1,200 to 1,600, about 47 to 62 kWh/m². Conversions of 15, 60 and 180 kWh/m² into outdoor years (about 0.24 to 0.32, about 1.0 to 1.3, and about 2.9 to 3.9 years). About 25 to 34 times acceleration for 60 kWh/m² in 14 days. About 0.94% a year from 2.83% over three years. About 20% a year from 14.2% over 258 days | Our calculation. That UV dose alone determines degradation, and that degradation proceeds at a constant rate, are this article's assumptions. Temperature, humidity, light-dark cycling and visible light are not included | Our calculation |
| The title, scope and publication status of IEC TS 63624-1. A 20-year-plus outdoor track record | Treated as future matters because they could not be confirmed from official public information, or because they cannot yet exist given the history of the technology (commentary) | Not yet confirmed |
| The framing of three yardsticks. Reading tests as nets for catching known failure modes. The reading on reversible degradation and measurement timing, and that continuous-illumination tests may be too harsh or may miss things. The action-spectrum concept and the need to set acceleration conditions from the materials side. Framing the need to check with separate tests that no other stress has crept in. How to read companies' durability claims | This article's own framing and commentary based on published content. Not views expressed by the institutions or authors | Commentary |
| That Figs. 1, 2 and 3 are explanatory drawings rather than real test data, and that the hero image and Fig. 4 are AI-generated images | Our note (commentary) | Commentary |
Last updated 25 September 2026. Sources are limited to primary material (IEC webstore standard pages, the ISOS consensus statement and peer-reviewed papers). Because the full texts of the standards are paid, the article stays within the published titles and scope summaries, and what peer-reviewed papers citing them say. The content and publication status of IEC TS 63624-1 are not stated because this article could not confirm them from official public information. The outdoor-trial figures quoted here differ in structure, encapsulation, climate, duration and evaluation method, and cannot be compared directly. All figures are explanatory concept graphics. Figs. 1, 2 and 3 are vector drawings; the hero image and Fig. 4 are AI-generated images, and none of them shows a real test site, equipment or product.