Services > Advanced Field Testing > Yield Loss Investigation & Root Cause Analysis
Yield Loss Investigation & Root Cause Analysis
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Electroluminescence (EL) Testing
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Infrared Thermography
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IV Curve Tracing
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Visual Inspection
Find where performance losses are coming from
When a solar PV system produces less energy than expected, the cause is not always obvious. The issue may sit at module level, string level, inverter block level, or somewhere in the balance of system.
Some problems are visible. Others only appear in operating data, thermal images, EL images, IV curves, or electrical measurements. A yield loss investigation helps move the discussion from “the system is underperforming” to a clearer view of what is happening, where it is happening, and what should be checked next.
Intertek CEA combines field inspection, electrical testing, image-based methods, and root-cause analysis to help owners, operators, investors, and EPCs understand performance losses and make better repair, warranty, or remediation decisions.
When this inspection helps
The solar PV system is producing less energy than expected.
Performance losses are visible in monitoring data, but the cause is unclear.
A drop in yield appeared after site work, maintenance, cleaning, storms, or other events.
Losses appear to be concentrated in certain strings, rows, inverter blocks, or areas of the site.
Modules show hotspots, visible changes, cracks, corrosion, or other signs of degradation.
You need evidence for warranty discussions, repair planning, or internal technical review.
You need to understand whether the problem is isolated, repeated, or systemic.
What we may test
The right inspection method depends on where the loss appears, what type of fault is suspected, and what evidence is needed to support repair, warranty, insurance, or root-cause decisions. Intertek CEA may combine image-based field methods, electrical measurements, on-site inspection, and laboratory testing where needed.
| Method | What it helps identify | When it is useful |
|---|---|---|
| Visual / On-site inspection | Visible site conditions, physical damage, installation issues, damaged components, and other field observations that may help explain performance loss or failure. | Useful as a starting point when failures such as glass breakage, corrosion, hotspots, or other visible issues need to be assessed in the field. |
| Thermography | Hotspots, affected modules or strings, failed substrings, thermal irregularities, and operating issues that appear under the right field conditions. | Useful for broad site screening and for identifying areas that may need closer follow-up. |
| EL testing | Hidden cell cracks, inactive cell areas, cell-level defects, and internal module damage that may not be visible from the outside. | Useful when module-level damage or degradation may be contributing to yield loss or recurring defects. |
| IV curve tracing | Electrical performance behavior of modules, strings, or sample groups. | Useful when the investigation needs to confirm whether modules or strings are producing as expected. |
| Structural evaluation | Mounting, loading, installation, or structural conditions that may contribute to module damage such as glass breakage. | Useful when the failure may be linked to mounting conditions, installation practices, mechanical stress, or site-specific structural factors. |
| Laboratory testing | Failure mechanisms that cannot be fully confirmed through field inspection alone. | Useful when field evidence is not enough to isolate the true source of the problem or when deeper root-cause confirmation is needed. |
The exact method mix depends on the suspected cause, site conditions, inspection objective, and whether the results need to support repair planning, warranty discussions, insurance documentation, or deeper root-cause analysis.
How we decide the right scope
The final inspection plan depends on the loss pattern, the available data, and what decision the results need to support.
What does the performance data show?
A sudden drop in yield may point to a recent event, site work, equipment change, or electrical fault. A gradual decline may point to degradation, soiling, shading, recurring module issues, or ageing effects. The inspection scope should start with the pattern in the data.
Where is the loss concentrated?
If the loss appears across the full site, the investigation may need broad screening. If it is concentrated in specific strings, rows, combiner boxes, or inverter blocks, targeted testing may be more useful.
What type of issue is suspected?
Different causes require different evidence. Hotspots, cell cracks, failed substrings, insulation issues, glass breakage, corrosion, connector faults, and shading problems do not all show up in the same way.
What level of proof is needed?
An internal maintenance decision may need less documentation than a warranty claim, supplier dispute, insurance discussion, or investor review. The reporting format should match how the findings will be used.
Is field evidence enough?
Some root-cause investigations can be resolved through field testing. Others may require laboratory testing, structural review, design review, or a deeper technical investigation to confirm the underlying cause.
What you get
The report should give your team a clear view of:
Where performance losses or anomalies are located
Whether the issue appears isolated, repeated, or systemic
Which modules, strings, areas, or inverter blocks are affected
What visible, thermal, cell-level, or electrical findings were observed
Which findings may explain the yield loss
Whether additional field testing, laboratory testing, or design review is recommended
Which actions may support repair planning, warranty discussions, or further root-cause analysis
Request a commissioning field testing plan
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