5 Unmissable Signs of Panel Cracks That Cause Reduced Power Output

Table of Contents

• Why you should suspect a cracked panel when power output is low

• Sign 1 Linear cracks and spiderweb-like cracks on the surface glass

• Sign 2: Visual changes suggesting internal deterioration, such as cloudiness or discoloration

• Sign 3: Localized anomalies caused by rainwater ingress or uneven soiling

• Sign 4 Unnatural variations in power generation and voltage per string

• Small changes when compared with Sign 5 inspection photos and past records

• On-site inspection flow when a cracked panel is found

• Record Management Practices to Ensure Declines in Power Generation Are Not Overlooked

• Summary

Reasons to suspect panel cracking when power output is low

When a solar power generation system continues to show low output, the first things often checked are the weather, solar irradiance, temperature, shading, dirt, and the stop history of the power conditioner. These are typical causes of reduced generation and are items you should prioritize in practice. However, one cause that is easily overlooked on site is cracks in the solar panels.

Panel cracks, even small hairline ones that only appear minor, can potentially affect power generation performance and safety. Damage that seems to be limited to the surface glass may have also affected internal cells, wiring, the encapsulant, or the backsheet. In addition, if moisture can more easily enter through the cracked area, over time this can lead to reduced insulation performance, corrosion, localized heating, and decreased output.

One important point to note is that panel cracks do not necessarily manifest as a sudden drop in power generation. Depending on the crack’s location and extent, the string configuration, irradiance conditions, and the granularity of monitoring data, anomalies can be hard to detect by looking only at daily generation. In particular, when generation declines gradually, it can be mistaken for aging-related degradation or seasonal variation, delaying the discovery of panel cracks.

Furthermore, because solar power plants have many panels, it takes time to inspect every panel closely by eye. Even for residential systems, when panels are installed on a roof it is difficult to get close to inspect them, and small cracks can be missed by visual inspection from the ground alone. When you notice a drop in power output, it is important to look for signs of cracked panels using both numerical data and on-site photographs.

This article outlines five signs of panel cracking that field personnel should not overlook, as they can lead to reduced power generation. It explains how to assess cracks not only by simply checking whether a panel is "cracked" but by combining visual inspection, power generation data, historical records, post-rain conditions, and other factors.

Sign 1 Linear cracks and spiderweb-like cracks in the surface glass

The most obvious sign is linear cracks or spiderweb-like fractures visible on the panel’s glass surface. Falling or flying objects, hail, snow loads, stepping on the panels during work, or deformation of the mounting structure or fixings can cause cracks to form on the panel surface. If there are visibly apparent cracks, those areas should be prioritized for inspection as candidate causes of reduced power generation.

Linear cracks may extend from the corner toward the center, or they may appear to run along the cell boundaries. Spiderweb-like cracks can appear as fine fractures radiating outward from the point of impact. Because these cracks can be difficult to see due to reflections on sunny days, it's important to check by changing the viewing angle. Even if they are not visible when viewed straight on, thin cracks may become apparent when viewed from an oblique angle.

What you need to be careful about with cracks on a panel surface is not to judge their impact based solely on the size of the crack. What looks like a small hairline crack may still affect the electrical pathways of the cells. Also, even if a crack is not currently reflected significantly in the power output, degradation can progress later due to ingress of rainwater or moisture. If you find surface cracks on equipment that has been experiencing persistently low power output, do not dismiss them as merely cosmetic; you need to check the relationship between the affected panel’s location, the string, and the power generation data.

During visual inspections, the panel edges and areas around mounting hardware are also easy to overlook. While cracks in the central area are relatively easy to spot, hairline cracks near the frame and chips at the corners can be masked by dirt or shadows and are therefore difficult to distinguish. Especially in locations with strong winds, in regions with snowfall, or where nearby trees or flying debris pose a risk, you should carefully inspect the corners and edges for damage.

Also, when inspecting cracked panels, safety precautions are essential. If glass shards are loose or the surface is damaged, touching them carelessly can result in injury. Inspections on roofs or sloped terrain carry a risk of falling. Because energized equipment poses electrical hazards, it is important to follow on-site rules and, when necessary, have inspections carried out by specialized inspection teams.

When investigating the causes of low power generation, cracks in the surface glass are often assumed to be "obvious at a glance," but in reality they can be missed because of light reflection, dirt, distance, and shooting conditions. During routine inspections, take and keep photographs not only from the same angle but from multiple directions, and ensure they can be enlarged later for review, as this leads to the detection of minute cracks.

Sign 2: Visual changes suggesting internal degradation, such as cloudiness or discoloration

Signs of panel cracking are not limited to obvious fractures. Even if cracks in the surface glass are not noticeable, internal damage can appear as clouding, discoloration, burn-like marks, or unnatural patterns around the cells. In systems with low power output, these visual changes should also be checked carefully.

White clouding can appear as a sign of degradation at the boundary between the panel’s encapsulant and the glass surface. If there are cracks or fine damage, the panel becomes more susceptible to the effects of moisture and air, which can change how the interior looks. When you see areas that appear white or cloudy, inspect the surrounding area for cracks, delamination, discoloration, or dirt deposits.

Discoloration is also an important sign. If only part of a cell appears brownish, looks darkened, or has a different hue compared with its surroundings, it may be related to localized heating or internal degradation. Of course, similar appearances can result from mere shadows, surface dirt, bird droppings, traces of fallen leaves, or uneven cleaning. For that reason, it is important not to make a definitive judgment based on appearance alone, and to distinguish between dirt that can be wiped away and changes that remain internal.

Visual changes that suggest internal degradation may be related to a decline in power generation, or they may not yet correspond to significant numerical changes. However, when part of a panel becomes unable to generate properly, it can affect the output of the entire string. In particular, if a single panel within the same string is abnormal, that effect can appear in the surrounding data.

When checking on site, it is effective not to view the panel that appears abnormal in isolation, but to compare it with surrounding panels in the same row, the same orientation, and the same tilt. If, compared with panels under the same conditions, a single panel has a different color, is cloudy only in part, or has cell boundaries that look unnatural, you should record it. Small differences that you might not notice by simply looking at the whole array become easier to see when you place photos side by side for comparison.

Also, cloudiness or discoloration can look very different depending on photographic conditions. They can be hard to see under strong reflections on sunny days, and may become more noticeable when photographed on cloudy days or from an oblique angle. Conversely, water droplets or surface reflections can make something appear to be an abnormality. Therefore, areas of concern should not be judged based on a single inspection; if possible, recheck them on another day or under different conditions.

When investigating why power generation is low, the numbers on the monitoring screen alone cannot capture visual changes such as clouding or discoloration. That is precisely why regular photographic records are meaningful. By comparing past photos with current ones, you can notice white clouding or discoloration that did not exist before. Even if a panel crack itself is not visible, changes suggestive of internal degradation can be clues to reduced power output.

Sign 3 Localized abnormalities caused by rainwater ingress or uneven dirt accumulation

To avoid overlooking panel cracks, it is also important to pay attention to conditions after rain or on days with high humidity. On panels with cracks or gaps, rainwater can enter and fine dirt can remain along the fissures. Anomalies that were not noticeable in clear weather may become more visible after the rain.

For example, if a thin linear stain remains on the surface of a panel, there may be a crack beneath it. After rainwater flows, dust or sand can remain along cracks or level differences and appear as a line. It can be difficult to distinguish from simple watermarks or flow marks, but be cautious if dirt repeatedly accumulates in the same spot, if the line is not seen on surrounding panels, or if a mark remains after cleaning.

Also, if it appears that moisture has entered the inside of the panel or if clouding remains beneath the glass surface, these should also be checked. Surface water droplets will disappear once dry, but moisture that has penetrated inside or clouding caused by degradation may remain even after drying. Such conditions can affect the panel’s insulation performance and long-term reliability, so they should be recorded regardless of whether there is a reduction in power generation.

Uneven accumulation of dirt also affects power generation. When dirt tends to gather in cracked or chipped areas, it can create a local shading effect. Even small amounts of dirt can affect power output depending on the position of the cells and the string configuration. In particular, if leaves, bird droppings, or dust tend to remain in the same spots, you should check not only for insufficient cleaning but also whether surface irregularities or damage are involved.

Anomalies caused by rainwater intrusion or uneven soiling can be difficult to judge from photographs alone. Therefore, it is important to record when a photo was taken during inspections. Keeping track of conditions—such as clear weather, after rain, before cleaning, and after cleaning—makes it easier to determine whether the same soiling is recurring or temporary. To investigate the cause of low power generation, it is important to match the dates of the photos with the generation data.

Also, panels that show abnormalities after rain are worth checking again once they have dried. If lines are visible right after the rain and faint traces remain after drying, surface scratches or cracks may be hiding underneath. Conversely, if they disappear completely after drying, the effect may have been caused by water droplets or surface dirt. By observing the panel at different times in this way, you can narrow down the likelihood of a panel crack.

For installations with low power output, it is important not to attribute an abnormality to a single cause but to consider the on-site environment as well. If there are conditions that tend to impose stress or soiling on panel surfaces—such as nearby trees, strong winds that stir up dust, birds gathering, snowfall or icing, or construction being carried out nearby—attention should be paid to cracks and micro-damage. Uneven patterns of rainwater or dirt can provide clues to locating those small damages.

Sign 4: Unnatural variations in power output and voltage per string

Cracked panels can leave signs not only on their appearance but also in the power generation data. In particular, on systems that allow checking generation, voltage, current, and operating status by string, it is important to look for any unusual discrepancies between strings under the same conditions. If you feel the generation output is low, looking only at the total for the entire facility can cause you to miss anomalies at the individual panel level.

If a string is made up of the same orientation, the same tilt, the same number of panels, and similar solar irradiance conditions, its generation trend is likely to be similar. Nevertheless, if only a particular string has lower generation, a slow rise on sunny days, midday output that plateaus, or voltage or current trends that differ from surrounding strings, these can be prompts to suspect on-site anomalies, including cracked panels.

However, you cannot definitively conclude that panels are cracked based solely on variations in per-string data. There are other causes such as shading, dirt, poor connections, equipment-side control, measurement errors, differences in azimuth and tilt, cable routing, and uneven solar irradiation. The important thing is to identify the strings that show anomalies in the data and focus on visually inspecting the panels included in those strings. This makes it easier to narrow down the inspection area even in large solar power plants.

When reviewing data, it's useful to look not only at a single day's power generation but also at trends over multiple days. On cloudy or rainy days, solar irradiance is unstable and differences between strings can be difficult to discern. Comparing data from sunny days with stable irradiance makes it easier to identify anomalous strings. Also, because the way shadows fall changes with the seasons, comparing with past data from the same period is helpful.

The impact of panel cracks does not always appear as a large drop in power generation. Fine cracks or anomalies in a few cells can look like only a small difference when viewed from the total power output of the installation. The larger the installation, the more likely single-panel anomalies will be masked if you look only at the overall output. Therefore, when investigating the cause of low power generation on site, it is important to dig down step by step from the overall value to string-level values, and then to on-site photographs.

Also, if the correspondence between string-level data and on-site locations is not organized, even when an anomaly is detected you will not know which panel to check on site. If the numbers on the drawings, the row numbers on site, the string numbers on the monitoring screen, and the photo locations do not match, inspections take longer and oversights increase. Detecting cracked panels requires not only the data itself but also management that links the data to the site.

If you find an abnormal variation between strings, you not only check each panel within the same string one by one, but also look for environmental differences with surrounding strings. Check whether there are objects casting shadows nearby, whether the amount of dirt differs, and whether there are differences in the tilt or fastening condition of the mounting structure. If you find surface cracks, whitening, discoloration, or uneven soiling among these, you can further investigate the possibility that panel cracks are related to a reduction in power output.

Sign 5: Small changes observed when compared with inspection photos and past records

Comparing current conditions with past inspection photos and records is essential to avoid overlooking panel cracks. Seeing the site only once can make it difficult to determine whether small cracks or discoloration are long-standing or recently developed. Rather than rushing to take photos after power output has already declined, keeping routine records that allow for comparison leads to earlier detection.

When compared with past photos, you may notice changes that were overlooked on site. These are small differences such as a linear shadow that wasn't there before, corner chipping that has widened, an increase in the area of clouding, a change in how dirt accumulates, or a single item in the same row changing in color. These are difficult to judge on their own, but when viewed in a time series they become easier to interpret as the progression of an anomaly.

When comparing inspection photos, it is important to keep the shooting position and angle as consistent as possible. If you take photos from different angles each time, differences in reflections and shadows can make defects appear or disappear. Establishing a reference position, shooting direction, and shooting range for each row makes it easier to compare with past images. In large power plants, linking area names, row numbers, and panel locations to the photo records makes them easier to find later.

When investigating the causes of decreased power output, it is important to view changes in the power generation data and changes in photographs on the same timeline. For example, if the output of a particular string becomes lower from a certain period and changes on the panel surface can be confirmed in photographs taken before and after that period, it becomes easier to narrow down the cause. Conversely, if there are changes visible in photographs but no change in the generation data, those observations can serve as a basis for deciding on continued monitoring or additional inspection.

When keeping historical records, it is effective to include not only photographs but also the weather, inspection dates, cleaning dates, locations of abnormalities, repair history, and trends in power generation. Cracks in panels are not necessarily discovered immediately after an impact. Keeping inspection records after typhoons, heavy snow, hail, strong winds, nearby work, and similar events makes it easier to trace when an abnormality may have occurred if you later find that power generation is low.

Also, on sites where inspection personnel change, the quality of records greatly affects detection accuracy. If one inspector records a small crack as an anomaly while another overlooks it, continuous management becomes difficult. By standardizing how photos are taken, how anomalies are recorded, and how comments are left, it becomes easier to verify using the same criteria even when inspectors change.

To detect small changes, it is important not to rely solely on on-site perception. The human eye tends to overlook abnormalities once it becomes accustomed to them. When you inspect the same equipment repeatedly, you may fail to notice gradual clouding or discoloration. Comparing current conditions with past photographs is an effective way to prevent such oversights caused by familiarity. To quickly identify the causes of low power generation, records should be treated not as mere archives but as inspection data used for comparison.

On-site steps to follow when you find a cracked panel

When you find what appears to be a sign of a cracked panel, it's important not to jump to conclusions but to proceed with an on-site inspection and data verification in that order. First, secure the area and avoid touching the damaged part unnecessarily. If there is broken glass, follow the site's safety standards, as there is a risk of injury, electric shock, and falling objects.

Next, accurately record the location of the anomaly. Note the area within the plant, the row, the tier, the panel position, nearby landmarks, and the correspondence with the string number. For residential systems, also record information that will allow later identification, such as the orientation of the roof plane, the installation row, and how many panels it is from the edge. If the location information is vague, you may not be able to find the same panel during subsequent checks, which can delay response.

Next, take photos under multiple conditions. Taking an overall shot, photos comparing the surrounding panels, a close-up of the abnormal area, and a shot from an oblique angle will make later assessment easier. If reflections make cracks hard to see, change the shooting angle. If moisture or dirt may be involved, recording the condition before and after cleaning and after drying will make it easier to determine whether it is surface contamination or an internal abnormality.

After that, cross-check with the power generation data. Check the power output, voltage, current, shutdown history, and alert history of the string that includes the panel in question. See whether there is a decline compared with strings under the same conditions, and whether the timing when abnormalities began matches the timing of the observed appearance changes. It is important here not to conclude that a crack is the cause of the power drop just because a crack was found; shadows, dirt, poor connections, and equipment-side factors must also be checked in parallel.

Consider conducting a detailed inspection as necessary. If internal damage or localized heating that cannot be determined from appearance alone is suspected, specialized verification methods may be required. If it is difficult for on-site personnel to make a judgment alone, it is important to share information among stakeholders—such as facility managers, construction personnel, and maintenance staff—and determine a course of action.

Consistency in record-keeping is also important when responding after finding a cracked panel. Recording the date the anomaly was found, the person who checked it, photos, power generation data, actions taken, and the scheduled follow-up inspection makes it easier to track progress later. Even if a decision about repair or replacement is required, organized records make explanations easier. To resolve issues of low power output, it is essential not to leave on-site findings as one-offs but to accumulate them as data.

An Approach to Record Management That Doesn’t Overlook Declines in Power Generation

To detect reduced power output caused by cracked panels early, not only the inspections themselves but also a system for managing records is important. If you try to review the past after discovering low output, it will take time to identify the cause if you don't know where photos were taken, the date they were taken, which string they belong to, or if you cannot cross-reference them with historical data.

In record management, the first thing to focus on is linking site photographs with power generation data. A decline in output appears as numbers, while a cracked panel appears as a visual condition on site. If these two are managed separately, it becomes difficult to identify correlations between anomalies. By attaching location information and notes to photos and associating them with strings and equipment drawings, it becomes easier to move from a data anomaly to on-site verification.

Next, it is also important to decide photography rules for regular inspections. Overall photos alone make small cracks difficult to find, while close-up photos alone make it hard to identify the location. If you standardize the shooting approach—overall, by row, abnormal areas, and surrounding comparison—you will find it easier to judge when reviewing later. Recording the weather at the time of shooting and the condition before and after cleaning also helps distinguish dirt from damage.

Also, rather than inspecting only when power output is low, it is important to record the condition during normal operation. Photos taken only during anomalies don't show what has changed. Only with photos and data from normal conditions can you estimate when cracks, clouding, discoloration, or uneven soiling began. Keeping records is particularly valuable before and after major weather events.

Site records need to be kept so that relevant personnel can check them immediately. If photos are scattered across individual staff devices or personal folders, they cannot be found when needed. It is desirable to organize them by equipment, area, date, and type of anomaly, and make them available for review together with power generation data and inspection notes. Speed is also important when responding to a decrease in power generation. If simply locating records takes time, it delays identifying the cause.

Furthermore, visual abnormalities such as cracked panels tend to become information noticed only by the person who went to the site. However, if photos and notes are made easy to share, remote managers and multiple personnel can check the same information. This reduces overlooked anomalies and helps curb variability in judgments. For systems with low power output, it is important to have a setup where on-site staff and managers can narrow down causes while viewing the same information.

Record-keeping to quickly detect cracked panels is not particularly difficult. The important thing is not to keep power generation data, on-site photos, location information, and inspection notes separate. Treating these as a single set of information makes it easier to investigate the causes of reduced power output. Especially when managing installations with a large number of panels or multiple sites, organizing records directly affects the quality of inspections.

Summary

When low power output persists, it is important to check the weather, solar irradiance, shading, soiling, and equipment shutdowns. However, that alone can still lead to missing abnormalities caused by cracked panels. Panel cracks can appear as obvious glass breakage, but may also manifest as clouding, discoloration, rainwater stains, uneven soiling, variations in string-level data, or differences compared with past photos.

Signs you must not overlook include linear cracks in the surface glass or spiderweb-like fractures, clouding or discoloration suggesting internal degradation, ingress of rainwater or uneven soiling, unusual discrepancies in power output or voltage among strings, and small changes compared with past records. None of these alone can definitively identify the cause, but by combining multiple pieces of information it becomes easier to narrow down the cause of reduced power output.

On site, when an anomaly is found, it is important to ensure safety, record the location accurately, photograph it from multiple angles, and cross-check with power generation data. Additionally, accumulating photos and data during normal operation makes it easier to compare when an anomaly occurs. Because panel cracks can begin as small visual changes, a system of daily records and comparisons leads to early detection.

To reliably track declines in power output, it is important to manage site photos, inspection notes, location information, and generation data together and to ensure stakeholders can view the same information. If you want to reduce overlooked panel cracks and speed up identification of the factors causing the decline, consider starting by reviewing your record-management system to link on-site inspections with data verification.