# Solar Panel Testing: EL, I-V and Thermography | Ecobaterías

> Solar panel testing in Chile: electroluminescence, I-V curve, IEC TS 62446-3 thermography and insulation tests, with a report for every module. Book a visit.

Canonical: https://ecobaterias.org/en/solar-panel-testing.html · Language: en · Alternate (es): https://ecobaterias.org/diagnostico-paneles-solares.html · Updated: 2026-09-26

Solar panels · Testing

# Solar panel testing: electro­luminescence, I-V curve and thermography

For plant and PMGD owners, operations and maintenance (O&M) contractors, insurers and buyers of used modules. We test at your plant or in our lab, deliver a report for every module and tell you what gets repaired, what gets reused and what gets recycled.

Updated September 26, 2026 · Reviewed by the Ecobaterías technical team

[Book a test](https://ecobaterias.org/en/contacto.html?segmento=diagnostico-paneles)[Message us on WhatsApp](https://wa.me/56940118111?text=Hi%2C%20I%20need%20solar%20panels%20tested.%20Quantity%2C%20model%20and%20plant%20location%3A%20)

## A report for every module

Serial number, electroluminescence image, I-V curve corrected to STC, insulation, bypass diodes and the recommended route: repair, reuse or recycle.

In the lab: 6 minutes per module · 50–100 modules per day.

- **6 min** — base test protocol per module in the lab
- **50–100** — modules per day in the lab
- **≥ 40 MΩ·m²** — wet insulation needed for a module to pass (IEC 61215-2)
- **≥ 600 W/m²** — minimum irradiance for valid thermography (IEC TS 62446-3)

Sources: Ecobaterías test protocol · [IEC 61215-2:2021, MQT 15 (Millennial Solar summary)](https://en.millennialsolar.com/news/314.html) · [IEC TS 62446-3:2017](https://webstore.iec.ch/en/publication/28628) · 2026-09-26

- **A report for every module** with serial number, EL image, I-V curve and insulation
- **At your plant or in our lab** with sampling for large plants
- **A reply within 48 business hours** with the scope and sampling plan
- **Coordinated pickup** with licensed transport across Chile

Ecobaterías tests solar panels at the customer’s solar plant or in the lab, with visual inspection, infrared thermography, electroluminescence (EL), I-V curves corrected to standard test conditions, dry and wet insulation tests, bypass diode checks and detection of potential-induced degradation (PID). We deliver a report for every module with its serial number, measured power as a percentage of nameplate and the recommended route: repair, reuse or recycle. In the lab, the base protocol takes 6 minutes per module.

- **Who it is for:** Plant and PMGD owners, O&M contractors, insurers and buyers of used modules
- **Tests:** Visual, IR thermography, electroluminescence, I-V curve at STC, insulation, wet leakage, bypass diodes and PID
- **Where:** At your plant: mobile on-site testing from Tarapacá to Coquimbo; in other regions, scheduled case by case. In our lab in Santiago: batches from anywhere in Chile, with coordinated pickup
- **Lab capacity:** 6 minutes per module · 50–100 modules per day
- **Deliverable:** A report for every module and a batch summary with the recommended route
- **Reference standards:** IEC 61215-2, IEC 60904-1, IEC 60891, IEC TS 60904-13, IEC TS 62446-3, IEC 62446-1 and IEC TS 62804-1
- **Price and lead time:** Confirmed in the quote · we reply within 48 business hours

The terms we use on this page. **STC** are the standard test conditions: 1,000 W/m² of irradiance and a cell temperature of 25 °C, the same conditions behind the nameplate rating. The **I-V curve** is the relationship between the module’s current and voltage; from it come the maximum power (Pmax), the open-circuit voltage (Voc), the short-circuit current (Isc) and the fill factor (FF). **Electroluminescence (EL)** is an image taken in the dark while current is injected into the module: healthy cells emit near-infrared light, peaking near 1,150 nm, and cracks show up dark. **Bypass diodes** sit in the junction box and route current around a group of cells (a substring) when it is shaded or fails. PMGD are Chile’s small distributed generation plants (pequeños medios de generación distribuida). More terms in the [technical glossary](https://ecobaterias.org/en/glossary.html).

## Who is it for and what is it used for?

Testing answers a specific question and ends in a decision. These are its typical uses:

Typical uses of solar panel testing and what you get in each case

| Use | Question it answers | Key tests | What you get |
|---|---|---|---|
| Manufacturer warranty claim | Is the power loss or defect a manufacturing issue? | I-V curve at STC, electroluminescence and visual inspection by serial number | A report for every module to support the claim |
| Insurance after hail or wind | How many modules were damaged, and which ones can go back into service? | Module-by-module testing: visual, electroluminescence, I-V curve and insulation | Count by type of damage and the class of each module |
| Repowering | Which decommissioned modules can be reused or sold? | Batch sampling and testing of every module that will be sold | P1, P2, P3 or recycling class for each module |
| Buying used modules or a plant | How much real power does what I am buying have? | I-V curve at STC, electroluminescence, insulation and wet leakage | Measured power against nameplate and defects per module |
| Operations and maintenance (O&M) | Where is energy being lost, and what is a safety risk? | Thermography, string I-V curves and Voc per module | List of strings and modules that need work |

Sources: test report uses (warranty, insurance, decommissioning and buying used modules) described by [2nd Cycle, PV Module Testing](https://www.2ndcycle.at/en/pv-modulprufung-1) · string tests per IEC 62446-1 · P1–P3 classes: Ecobaterías in-house protocol.

If you plan to file a warranty claim, have the modules tested before anyone works on them. According to the Ministry of Energy’s Hoja de Ruta de Economía Circular en Energía 2026–2030 (Circular Economy in Energy Roadmap), manufacturers’ warranties generally do not allow repair or reuse.

For repowering, see also [what to do with the modules removed from a plant](https://ecobaterias.org/en/solar-plant-repowering.html). If you are buying, see [how we present the measured data sheet for each refurbished panel](https://ecobaterias.org/en/refurbished-solar-panels.html). And if your plant has storage, we also offer [lithium battery testing with an SOH certificate](https://ecobaterias.org/en/diagnostico-baterias-litio.html). Every service line is listed under [services for batteries and solar panels](https://ecobaterias.org/en/servicios.html).

## What does each test detect?

Each test sees a different kind of fault, which is why testing combines several: thermography finds the module, electroluminescence shows the crack, the I-V curve measures how much power was lost and the insulation test tells you whether the module is safe.

What each test detects, how it is done and the reference standard

| Test | What it detects | How it is done and reference threshold | Standard | Where |
|---|---|---|---|---|
| Visual inspection | Broken glass, bubbles, delamination, burn marks, corrosion, damaged frame or junction box, and snail trails (dark lines that follow cell cracks) | At a minimum of 1,000 lux. Broken glass, burn marks or delamination reaching the module edge are rejected | IEC 61215-2:2021 (MQT 01) | Plant and lab |
| Infrared thermography | Hot spots, disconnected substrings, active diodes and faulty connections | With the module operating, at least 600 W/m² in its plane, wind up to 28 km/h and up to 2 oktas of cloud (2/8 of the sky). Cell 10–40 K hotter: class 2; more than 40 K: class 3, safety-relevant | IEC TS 62446-3:2017 | Plant |
| Electroluminescence (EL) | Microcracks, broken cells, cut fingers, inactive areas and PID patterns | Module under forward bias in the dark; images at Isc and at Isc/10 | IEC TS 60904-13:2018 | Lab (dark cabin) and plant, at night |
| I-V curve at STC | Maximum power (Pmax), Voc, Isc and fill factor (FF) | In the lab, under a solar simulator (IEC 61215-2 calls for class CAA or better per IEC 60904-9); in the plant, correction to 1,000 W/m² and 25 °C | IEC 60904-1:2020 and IEC 60891:2021 | Plant and lab |
| Dry insulation | Insulation between live parts and the frame | Modules larger than 0.1 m²: resistance times area of at least 40 MΩ·m² | IEC 61215-2:2021 (MQT 03) | Plant and lab |
| Wet leakage | Moisture ingress and insulation failures in the backsheet or junction box | Module in a solution of up to 3,500 Ω·cm at 22 ± 2 °C; 500 V or the maximum system voltage, whichever is higher, for 2 min; passes with at least 40 MΩ·m² | IEC 61215-2:2021 (MQT 15) | Lab |
| Bypass diodes | Open or shorted diodes and disconnected substrings | Full Voc: healthy substrings; 2/3, 1/3 or 0 of Voc: one, two or three failed substrings. Then the diode is tested in forward and reverse | Voc method (IEA-PVPS T13-37:2026) · IEC 61215-2:2021 (MQT 18) | Plant and lab |
| PID | Potential-induced degradation, shunting or polarization type | Low-current EL image (Isc/10), which reveals shunts and PID, and power loss on the I-V curve | Detection: IEA-PVPS T13-10:2018 · PID tests: IEC TS 62804-1:2025, crystalline silicon only | Plant and lab |

Sources: IEC 61215-2:2021 preview and IEC listings for IEC 60904-1, IEC 60891, IEC TS 60904-13, IEC TS 62446-3 and IEC TS 62804-1 · IEA-PVPS T13-10:2018 (EL at Isc and Isc/10) and T13-37:2026 (Voc method for diodes) · insulation thresholds per Millennial Solar and Winaico · full links under “Sources.”

Dry testing alone is not enough. In a 2026 study of 37 modules from utility-scale plants, 8.1% failed the 40 MΩ·m² threshold dry and 21.6% failed it wet: five modules would have passed with a dry test only. In a mass-scale reuse project in Queensland (Australia), 331 of 2,200 modules (15%) failed wet leakage, and about 75% of those failures appeared in the first 10 seconds of the test.

### How to read an I-V curve

*Schematic I-V curve. Isc: short-circuit current. Voc: open-circuit voltage. Pmax: maximum power point, equal to Vmp × Imp. The fill factor (FF) is the green area divided by the dashed rectangle (Voc × Isc): the squarer the curve, the higher the FF. A module that loses power shows a lower Pmax against its nameplate.*

### Which faults are most common?

According to the IEA-PVPS failure review (T13-01:2014), the most important field failures are in the junction box, the glass, cell interconnections, the frame and the encapsulant (delamination). After 8 years in operation, the junction box and cables account for 12% of failures, burn marks for 10% and the encapsulant for 9%. Early in the service life, 5% of cases are transport damage. Snail trails appear 3 months to 1 year after installation and follow cell cracks: electroluminescence and the I-V curve tell you whether they affect power.

## At the plant or in the lab?

We test wherever it makes more sense for the batch. At the plant, the module is still installed or freshly removed and nothing is shipped. In the lab, conditions are controlled and the STC measurement is direct.

Testing at your plant or in our lab: what changes

| Aspect | At your plant | In our lab (Santiago) |
|---|---|---|
| Tests | Thermography, string or module I-V curves, Voc per module, array insulation and nighttime electroluminescence | Visual inspection and UV fluorescence, electroluminescence in a dark cabin, I-V curve under a solar simulator, insulation, wet leakage and diodes |
| Conditions | Thermography with at least 600 W/m², wind up to 28 km/h and a nearly clear sky; electroluminescence at night | Controlled: 1,000 W/m² and 25 °C, with a calibrated reference module |
| Throughput | An 8-hour night of electroluminescence typically covers a few hundred modules (industry reference) | 6 minutes per module · 50–100 modules per day |
| Best for | Operating plants, insurance events and locating faulty strings or modules without removing them | Removed or stacked modules, batches to be reused or sold, and claims that need an STC measurement |
| Logistics | Modules stay where they are | We coordinate pickup: freight transport for sound modules and licensed hazardous-waste transport if the batch is already waste |

Sources: [IEC TS 62446-3:2017](https://webstore.iec.ch/en/publication/28628) (thermography conditions) · [Sinovoltaics](https://sinovoltaics.com/technology/on-site-electroluminescence-testing-at-pv-power-plants-methodologies-and-applications/) (nighttime EL) · Ecobaterías test protocol: lab capacity, not a committed lead time.

### Drone or ground?

Drone thermography is the simplified inspection of IEC TS 62446-3: it covers the whole plant and flags modules with anomalies. Detailed ground inspection, electroluminescence and the I-V curve confirm the cause and the power loss. If you already have an aerial thermography report, we use it to choose which modules to test. When modules go to the lab, [we coordinate pickup and transport](https://ecobaterias.org/en/battery-solar-panel-collection-transport.html).

## How do you sample a large plant?

In a plant with tens of thousands of modules, you do not always need to test them all. The draft IEC PAS 63525, the IEC’s first document on photovoltaic module reuse (not yet published), proposes two approaches. IEA-PVPS summarizes them in its T13-37:2026 report:

Sampling or module-by-module testing: when each approach applies

| Situation | Approach | Minimum tests |
|---|---|---|
| Operating plant with even degradation and monitoring data | Statistical sampling per ISO 2859-1 | Pmax at STC, electroluminescence, detailed visual inspection and wet leakage |
| Plant damaged by hail or wind | Module by module | Visual inspection, I-V curve, dry insulation, diodes and electroluminescence |
| Modules stacked in a warehouse | Module by module | Same as above |
| Modules that will be sold | Module by module (recommended by the draft) | Same, plus a reuse label |

Source: [IEA-PVPS T13-37:2026, §3.1.2](https://iea-pvps.org/wp-content/uploads/2026/02/IEA-PVPS-T13-37-2026-REPORT-Second-Life-PV.pdf), on the draft IEC PAS 63525 (stage 40.99 as of August 7, 2026).

Sample size changes a lot with the ISO 2859-1 inspection level: in a plant of 125,000 modules, level G1 means 200 modules and level S3 only 32. We propose the level in the quote, based on how the report will be used and the monitoring data available.

Before sampling, we review the background. The guide from the European QUASAR project (2025) starts with a desk review: the plant’s annual loss should be below typical degradation (about 0.8% per year in that guide), and models with serial defects or market recalls are excluded. As a general reference, the median degradation measured by NREL is 0.5% per year.

## What does the report contain?

A report for every module and a batch summary. Each module is identified by its serial number, so the result works for a claim, an insurer or a sale.

- **Identification:** serial number, brand, model and nameplate data (Pmax, Voc, Isc and maximum system voltage); at the plant, the string as well.
- **Visual inspection:** defects found, with photographs.
- **Electroluminescence:** module image with defects marked (cracks, inactive cells, PID patterns).
- **I-V curve:** Pmax, Voc, Isc and FF corrected to STC, and power as a percentage of nameplate.
- **Electrical safety:** dry insulation and, if performed, wet leakage in MΩ·m²; condition of the bypass diodes.
- **Thermography (at the plant):** anomaly class 1, 2 or 3 per IEC TS 62446-3.
- **Class and route:** P1, P2, P3 or recycling, and the recommended action.
- **Batch summary:** modules by class and by 5 W power bin, defects by type and, if sampling was used, the plan and level applied.

The content follows what reuse schemes require. The R2v3 standard (Appendix G) requires telling the buyer the power measured at STC, its percentage of the design power and every repair performed. The draft IEC PAS 63525 calls for a reuse label that does not cover the original one and lists any repairs, and advises adding the measured I-V parameters. Our report is a technical report: it is not a product certification or an authorization from the SEC (Chile’s Superintendency of Electricity and Fuels).

## What happens after testing?

Testing ends in a route for each module. We use an in-house classification by percentage of nameplate power, together with the electroluminescence and insulation results.

From test result to the route for each module

| Test result | Route | Service |
|---|---|---|
| 85% or more of nameplate, no critical EL defects and correct insulation (class P1) | Direct reuse | [Solar panel reuse](https://ecobaterias.org/en/reutilizacion-paneles-solares.html) |
| Between 80 and 85% of nameplate (class P2) | Refurbishment and retest | [Refurbished solar panels](https://ecobaterias.org/en/refurbished-solar-panels.html) |
| Between 70 and 80% of nameplate (class P3) | Off-grid uses, subject to SEC requirements | [Solar panel reuse](https://ecobaterias.org/en/reutilizacion-paneles-solares.html) |
| Fault in the junction box, bypass diode, cable or connector, with sound glass | Repair and retest, with wet leakage unless only cables or connectors were replaced | [Solar panel repair](https://ecobaterias.org/en/solar-panel-repair.html) |
| Below 70% of nameplate, broken glass, delamination reaching the edge or insulation that does not recover | Recycling with a certificate | [Solar panel recycling](https://ecobaterias.org/en/solar-panel-recycling-chile.html) |
| PID pattern on electroluminescence | Graded by measured power: PID recovery is only partial | By class: P1, P2, P3 or recycling |

Sources: P1–P3 classes from the Ecobaterías test protocol (in-house classification, not a standard) · [IEA-PVPS T13-37:2026](https://iea-pvps.org/wp-content/uploads/2026/02/IEA-PVPS-T13-37-2026-REPORT-Second-Life-PV.pdf) (repairs) · [Scientific Reports, 2022](https://www.nature.com/articles/s41598-022-26310-y) (PID recovery).

Every repair, except replacing cables or connectors, is validated with a new wet leakage test, as IEA-PVPS recommends. PID recovery is not complete: efficiency comes back almost fully at high irradiance, but not at low irradiance. A module with broken glass is neither repaired nor sold. As an outside reference, the European CIRCUSOL project proposed treating a module as functional if it keeps at least 70% of its rated power; IEA-PVPS calls that threshold somewhat arbitrary until regulations exist.

## How we work: the step-by-step protocol

1. **Request and background**You tell us the quantity, brand, model, nameplate power, year, location and reason for testing, and send any monitoring data or thermography you have. We reply within 48 business hours with the scope, the sampling plan and the quote.
2. **On-site inspection**For field testing: thermography with at least 600 W/m² of irradiance per IEC TS 62446-3, string or module I-V curves corrected to STC with IEC 60891:2021, Voc per module to locate failed diodes and substrings, and electroluminescence at night.
3. **Intake and visual inspection**In the lab, the serial number, model and nameplate data are recorded; visual inspection at a minimum of 1,000 lux per IEC 61215-2:2021 and UV fluorescence.
4. **Electrical safety**Dry insulation (at least 40 MΩ·m²) and bypass diode testing. Wet leakage by sampling and on every repaired module, except those that only had cables or connectors replaced.
5. **Electroluminescence**EL imaging in a dark cabin per IEC TS 60904-13:2018, at Isc and, when looking for shunts or PID, at Isc/10.
6. **I-V curve at STC**Pmax, Voc, Isc and FF at 1,000 W/m² and 25 °C under a solar simulator with a calibrated reference module. Power is expressed as a percentage of nameplate.
7. **Report and decision**A report for every module and a batch summary, with each module’s class and the recommended route: repair, reuse or recycle.

In the lab, steps 3 to 6 take 6 minutes per module, with 50–100 modules per day. That is the lab’s capacity, not a committed lead time: the lead time for each batch is confirmed in the quote.

## Which panels do you test?

Which panels we test and with which tests

| Technology | Tests | Note |
|---|---|---|
| Mono and poly crystalline silicon, PERC and TOPCon, with 60 or 72 cells or 144 half cells | Every test on this page | Monofacial and bifacial glass-glass |
| Heterojunction (HJT) | Visual, thermography, electroluminescence, I-V curve, insulation and diodes | The PID standard IEC TS 62804-1 does not cover heterojunction |
| Thin film (CdTe, CIGS) | Visual, thermography, I-V curve and insulation | Quoted case by case; IEC TS 62804-1 does not apply |
| Modules with broken glass | Visual, electroluminescence and I-V curve, for the claim or the insurer | Not repaired or sold: they go to recycling |

Sources: scope of [IEC TS 62804-1:2025](https://webstore.iec.ch/en/publication/71747) (crystalline silicon; excludes thin film, tandem and heterojunction) · Ecobaterías in-house scope.

## Which standards do you use as a reference?

We cite these standards as test methods. They are not certifications held by Ecobaterías or by the module.

Reference IEC standards, with their official titles and what we use them for

| Standard | Official title | What we use it for |
|---|---|---|
| IEC 61215-2:2021 | *Terrestrial photovoltaic (PV) modules – Design qualification and type approval – Part 2: Test procedures* | Visual inspection (MQT 01), dry insulation (MQT 03), wet leakage (MQT 15) and bypass diodes (MQT 18) |
| IEC 60904-1:2020 | *Photovoltaic devices – Part 1: Measurement of photovoltaic current-voltage characteristics* | I-V curve measurement |
| IEC 60891:2021 | *Photovoltaic devices – Procedures for temperature and irradiance corrections to measured I-V characteristics* | Correcting field I-V curves to STC |
| IEC TS 60904-13:2018 | *Photovoltaic devices – Part 13: Electroluminescence of photovoltaic modules* | Electroluminescence imaging |
| IEC TS 62446-3:2017 | *Photovoltaic (PV) systems – Requirements for testing, documentation and maintenance – Part 3: Photovoltaic modules and plants – Outdoor infrared thermography* | On-site thermography and anomaly classes |
| IEC 62446-1:2016+AMD1:2018 | *Photovoltaic (PV) systems – Requirements for testing, documentation and maintenance – Part 1: Grid connected systems – Documentation, commissioning tests and inspection* | On-site string tests |
| IEC TS 62804-1:2025 | *Photovoltaic (PV) modules – Test methods for the detection of potential-induced degradation – Part 1: Crystalline silicon* | Reference for PID in crystalline silicon; does not cover thin film, tandem or heterojunction |
| IEC PAS 63525 (draft) | *Reuse of PV modules and circular economy* | Sampling approaches and the reuse label; not yet published |

Sources: titles as listed on webstore.iec.ch and in the official previews of IEC 61215-2 and IEC 62446-1 · IEC PAS 63525 status as of August 7, 2026 · full links under “Sources.”

## What do Chilean rules require?

- **SEC, module authorization:** the SEC authorizes modules by brand and model, based on IEC 61215 and IEC 61730 certificates for new products (Exempt Resolution 32,427/2020). There is no authorization path for used or refurbished modules. Each module keeps its brand, model and nameplate; the installation declared to the SEC is defined by the licensed electrical installer. We recommend checking with the SEC.
- **SEC, damaged modules:** Technical Instruction RGR No. 02/2024 prohibits installing modules with breaks or cracks. ITG RIC No. 9.1 requires authorized models in off-grid installations too.
- **SEC, array insulation:** RGR No. 02/2024 (Table 2) sets the test by system voltage (Voc at STC × 1.25): at 250 V with a minimum of 0.5 MΩ below 120 V; at 500 V with a minimum of 1 MΩ between 120 and 500 V; and at 1,000 V with a minimum of 1 MΩ above 500 V.
- **Hazardous waste:** according to Chile’s Ministry of Energy, a disused or damaged panel is handled as hazardous waste unless it is declassified under Supreme Decree (DS) 148/2003. If the batch is already waste, [we coordinate pickup with licensed hazardous-waste transport](https://ecobaterias.org/en/battery-solar-panel-collection-transport.html).
- **[Supreme Decree (DS) 22/2025](https://ecobaterias.org/en/ds-22-2025-solar-panels-epr.html):** sets collection and recovery targets for photovoltaic panels, from 10% in the third year up to 50% from the tenth, enforceable 24 months after its publication on May 7, 2026.
- **Chile’s Extended Producer Responsibility law (Ley REP, Law No. 20,920):** checking, cleaning or repairing a discarded product so it can be reused is preparation for reuse (art. 3 No. 18), and valorization (recovery) includes it alongside recycling (art. 3 No. 30). Testing is the first step to know which one applies.

Sources: [SEC, RGR No. 02/2024](https://www.sec.cl/sitio-web/wp-content/uploads/2025/01/RGR-N-02-2024-V11-destacada.pdf) · [SEC Exempt Resolution 32,427/2020](https://www.bcn.cl/leychile/navegar?idNorma=1146347) · [ITG RIC No. 9.1/2021](https://www.sec.cl/sitio-web/wp-content/uploads/2022/01/5-EXIGENCIAS-TECNICAS-DE-INSTALACIONES-FOTOVOLTAICAS-AISLADAS-ITG-V4.pdf) · [Circular Economy in Energy Roadmap](https://energia.gob.cl/sites/default/files/documentos/hoja_de_ruta_de_economia_circular_en_energia.pdf) · [Law 20,920](https://www.bcn.cl/leychile/navegar?idNorma=1090894) · 2026-09-26

## What does it cost and how long does it take?

Price and lead time are confirmed in the quote. They depend on:

- the number of modules, and whether all of them or a sample are tested;
- the tests you request, for example wet leakage or thermography;
- the location: your plant and its region, or our lab;
- the condition of the batch: installed, removed or stacked in a warehouse;
- whether pickup is needed, and with what kind of transport.

We reply within 48 business hours with a proposal. [Request your testing here](https://ecobaterias.org/en/contacto.html?segmento=diagnostico-paneles).

## Frequently asked questions

### How can I tell whether a solar panel is faulty or working properly?

A panel can look fine and still be losing power. Three tests confirm it: an I-V curve corrected to standard test conditions measures how much power it delivers against its nameplate; electroluminescence shows microcracks and inactive cells that the eye cannot see; and an insulation test tells you whether it is safe. If the Voc reads 2/3, 1/3 or 0 of normal, one, two or three substrings are disconnected or bypassed, and the next step is to test the bypass diodes.

### What is electroluminescence testing of solar panels?

It is an image of the module taken in the dark while current is injected under forward bias: healthy cells emit near-infrared light, while cracks, broken cells, cut fingers and inactive areas show up dark. Images are taken at the short-circuit current (Isc) and at one tenth of it, which reveals shunts and PID. The method is described in IEC TS 60904-13:2018.

### What does a solar panel’s I-V curve show?

It shows the current the panel delivers at each voltage. From it come the maximum power (Pmax), the open-circuit voltage (Voc), the short-circuit current (Isc) and the fill factor (FF). When measured in the field, it is corrected to standard test conditions (1,000 W/m² and 25 °C) with the procedures of IEC 60891:2021 so it can be compared with the manufacturer’s nameplate.

### What is thermography for, and what is a hot spot?

Infrared thermography measures the temperature of every cell while the plant is running. A hot spot is a cell or area hotter than its neighbors; the most common cause is a broken cell, but shading, soiling or a diode can also cause it. Under IEC TS 62446-3, a silicon cell 10 to 40 K hotter is a thermal anomaly, and more than 40 K is a safety-relevant anomaly. It requires at least 600 W/m² of irradiance.

### What is PID (potential-induced degradation)?

PID is the power loss caused by the high system voltage acting on the module. There are two types, shunting and polarization. It is detected with low-current electroluminescence. Recovery with nighttime reverse voltage, heat or UV light is only partial. The test standard, IEC TS 62804-1:2025, covers crystalline silicon only.

### How much does a solar panel degrade per year?

The median NREL found across about 2,000 measurements is 0.5% per year (Jordan and Kurtz). A module with defects, PID or mechanical damage degrades faster, so its real power is measured with an I-V curve at standard test conditions rather than estimated from its age.

### How long does a solar panel last?

It depends on the module and its history, which is why it is worth measuring. For reference, 23-year-old polycrystalline modules in Brazil still kept 87–88% of their nameplate power. In an Australian study of 3,749 decommissioned panels, 58% were still fit for a second life, with a median remaining useful life of about 12 years.

### How do you detect hail-damaged solar panels?

With module-by-module testing: visual inspection for glass and frame, electroluminescence for cell cracks that cannot be seen, an I-V curve for power loss and an insulation test for safety. The IEC draft on module reuse calls for testing every module in plants damaged by hail or wind. In Chile, the SEC prohibits installing modules with breaks or cracks.

### What is an insulation test?

It measures the resistance between the live parts of the panel and its frame to confirm there is no current leakage. In the wet leakage test the module is wetted with a conductive solution and the voltage is held for 2 minutes. A module larger than 0.1 m² passes with at least 40 MΩ·m² (IEC 61215-2). Dry testing alone is not enough: in a 2026 study, 8% failed dry and 22% failed wet.

### Drone or ground inspection: which is better?

They complement each other. Drone thermography is the simplified inspection of IEC TS 62446-3: it covers the whole plant and flags modules with anomalies. Detailed ground inspection, electroluminescence and the I-V curve confirm the cause and the power loss of those modules. To decide whether a module is repaired, reused or recycled, you need the detailed testing.

More answers in [frequently asked questions about batteries and solar panels](https://ecobaterias.org/en/faq.html).

## Sources

- IEC 61215-2:2021, *Terrestrial photovoltaic (PV) modules – Design qualification and type approval – Part 2: Test procedures* (official preview: MQT 01, 02, 03, 15 and 18). [standards.iteh.ai](https://cdn.standards.iteh.ai/samples/101269/e9c169bfdf004586a8c0cf8bf9e2a625/IEC-61215-2-2021.pdf)
- IEC 60904-1:2020, *Photovoltaic devices – Part 1: Measurement of photovoltaic current-voltage characteristics*. [webstore.iec.ch](https://webstore.iec.ch/en/publication/32004)
- IEC 60891:2021, ed. 3.0, *Photovoltaic devices – Procedures for temperature and irradiance corrections to measured I-V characteristics*. [webstore.iec.ch](https://webstore.iec.ch/en/publication/61766)
- IEC TS 60904-13:2018, *Photovoltaic devices – Part 13: Electroluminescence of photovoltaic modules*. [webstore.iec.ch](https://webstore.iec.ch/en/publication/26703)
- IEC TS 62446-3:2017, *Part 3: Photovoltaic modules and plants – Outdoor infrared thermography*. [webstore.iec.ch](https://webstore.iec.ch/en/publication/28628)
- IEC 62446-1:2016+AMD1:2018, *Part 1: Grid connected systems – Documentation, commissioning tests and inspection* (preview table of contents). [standards.iteh.ai](https://cdn.standards.iteh.ai/samples/20417/75e16a1faaab43febc2ef124e557c33d/IEC-62446-1-2016.pdf)
- IEC TS 62804-1:2025, ed. 2.0, *Photovoltaic (PV) modules – Test methods for the detection of potential-induced degradation – Part 1: Crystalline silicon*. [webstore.iec.ch](https://webstore.iec.ch/en/publication/71747)
- IEC PAS 63525 ED1, *Reuse of PV modules and circular economy*: project status (stage 40.99 as of August 7, 2026, not yet published). [iss.rs](https://iss.rs/en/project/show/iec:proj:120892)
- IEA-PVPS T13-37:2026, *Performance and Reliability Aspects of 2nd Life Photovoltaic Modules* (sampling, diodes, repairs and wet leakage). [iea-pvps.org](https://iea-pvps.org/wp-content/uploads/2026/02/IEA-PVPS-T13-37-2026-REPORT-Second-Life-PV.pdf)
- IEA-PVPS T13-10:2018, *Review on Infrared and Electroluminescence Imaging for PV Field Applications* (EL at Isc and Isc/10). [iea-pvps.org](https://iea-pvps.org/wp-content/uploads/2020/01/Review_on_IR_and_EL_Imaging_for_PV_Field_Applications_by_Task_13.pdf)
- Review of electroluminescence imaging of PV modules (silicon emission peaking near 1,150 nm). PubMed Central. [pmc.ncbi.nlm.nih.gov](https://pmc.ncbi.nlm.nih.gov/articles/PMC12029750/)
- IEA-PVPS T13-01:2014, *Review of Failures of Photovoltaic Modules* (failure statistics and snail trails). [iea-pvps.org](https://iea-pvps.org/wp-content/uploads/2020/01/IEA-PVPS_T13-01_2014_Review_of_Failures_of_Photovoltaic_Modules_Final.pdf)
- IEC 61215-2 dry insulation and wet leakage thresholds (secondary source). Millennial Solar. [millennialsolar.com](https://en.millennialsolar.com/news/314.html)
- Overview of the IEC 61215 tests (secondary source). Winaico. [winaico.com](https://winaico.com/blog/iec-61215/)
- Dry and wet insulation in 37 modules from utility-scale plants. *Sustainability* 18(3):1212, 2026. [mdpi.com](https://www.mdpi.com/2071-1050/18/3/1212)
- Mass-scale reuse project in Queensland: 15% wet leakage failures. pv magazine, August 13, 2026. [pv-magazine.com](https://www.pv-magazine.com/2026/08/13/mass-scale-reuse-pilot-project-finds-15-of-second-life-solar-modules-fail-to-meet-safety-requirements/)
- I-V screening of 3,749 decommissioned modules (ANU and CSIRO). pv magazine, August 19, 2026. [pv-magazine.com](https://www.pv-magazine.com/2026/08/19/i-v-screening-for-decommissioned-pv-modules/)
- 23-year-old polycrystalline modules in second life (UFSC, Brazil). pv magazine, March 31, 2026. [pv-magazine.com](https://www.pv-magazine.com/2026/03/31/extensive-testing-validates-reuse-of-23-year-old-second-life-polycrystalline-solar-modules/)
- Jordan and Kurtz, *Photovoltaic Degradation Rates — An Analytical Review*. NREL. [nrel.gov](https://docs.nrel.gov/docs/fy12osti/51664.pdf)
- Recovery of PID-affected modules. *Scientific Reports*, 2022. [nature.com](https://www.nature.com/articles/s41598-022-26310-y)
- On-site electroluminescence testing at PV power plants: methods and throughput per night. Sinovoltaics. [sinovoltaics.com](https://sinovoltaics.com/technology/on-site-electroluminescence-testing-at-pv-power-plants-methodologies-and-applications/)
- QUASAR project (EU), deliverable D2.2 (June 11, 2025): PV module reuse guide. [quasar-project.eu](https://quasar-project.eu/wp-content/uploads/2025/09/D2.2_Deliverable_Report_final_v1.0_watermark.pdf)
- 2nd Cycle, *PV Module Testing*: use cases for the test report. [2ndcycle.at](https://www.2ndcycle.at/en/pv-modulprufung-1)
- R2v3 (SERI), Appendix G: requirements for solar panel reuse (EnergyBin summary). [energybin.com](https://resources.energybin.com/solar-resources/r2-standard-for-solar-panel-reuse-and-recycling)
- SEC, Technical Instruction RGR No. 02/2024 (§8 and Table 2). [sec.cl](https://www.sec.cl/sitio-web/wp-content/uploads/2025/01/RGR-N-02-2024-V11-destacada.pdf)
- SEC, Exempt Resolution 32,427/2020: authorization of photovoltaic products by brand and model. Library of the National Congress of Chile. [bcn.cl](https://www.bcn.cl/leychile/navegar?idNorma=1146347)
- SEC, ITG RIC No. 9.1/2021: technical requirements for off-grid photovoltaic installations. [sec.cl](https://www.sec.cl/sitio-web/wp-content/uploads/2022/01/5-EXIGENCIAS-TECNICAS-DE-INSTALACIONES-FOTOVOLTAICAS-AISLADAS-ITG-V4.pdf)
- Ministry of Energy, Hoja de Ruta de Economía Circular en Energía 2026–2030 (Circular Economy in Energy Roadmap). [energia.gob.cl](https://energia.gob.cl/sites/default/files/documentos/hoja_de_ruta_de_economia_circular_en_energia.pdf)
- Law 20,920, art. 3 No. 18 and No. 30. Library of the National Congress of Chile. [bcn.cl](https://www.bcn.cl/leychile/navegar?idNorma=1090894)
- Supreme Decree (DS) 22/2025 of the Ministry of the Environment: collection and recovery targets for photovoltaic panels (Carey summary). [carey.cl](https://www.carey.cl/publican-decreto-que-establece-metas-de-recoleccion-y-valorizacion-de-residuos-de-pilas-y-aparatos-electricos-y-electronicos)
- Ecobaterías test protocol: lab times and P1–P3 classes (in-house thresholds, not a standard), 2026.

Updated September 26, 2026 · Reviewed by the Ecobaterías technical team

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Every module with measured power, an EL image and an insulation test.

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### [Solar plant repowering](https://ecobaterias.org/en/solar-plant-repowering.html)

What to do with removed modules: test, reuse and recycle.

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contacto@ecobaterias.org · WhatsApp +56 9 4011 8111 · Santiago and Viña del Mar, Chile.
Ecobaterías is a Chilean company that recycles, repairs and reuses lithium batteries and solar panels.