4 Points to Check for Mounting-Frame Warping and Tilt to Prevent Declines in Power Generation

When you feel that power generation from a photovoltaic system is low, many personnel in charge first check the weather, panel soiling, shading, the power conditioner's shutdown history, output curtailment, and the monitoring equipment's displayed values. These are important checks, but what is easily overlooked is deformation or tilt of the mounting structure. The mounting structure is the foundation that supports the solar panels and affects installation angle, orientation, surface alignment, and how securely they are fixed. Depending on its condition, it can affect how solar radiation is received, drainage, wind-induced sway, remaining dirt on panel surfaces, and loads on wiring and fastening hardware.

Especially for ground-mounted installations, rooftop installations, sloped sites, developed/fill sites, weak ground, snowy regions, and locations exposed to strong winds, even if there are no issues at the time of installation, the condition of the mounting structures may change over time. When investigating the causes of reduced power output, checking structural changes as well as electrical measurements makes it easier to isolate anomalies.

Table of Contents

• Why deformation and tilt of the mounting structure lead to reduced power generation

• Point 1: Check the alignment of the panel surfaces and changes in tilt angle

• Point 2: Check for settlement or loosening of foundations, support posts, and fastenings

• Point 3: Check for poor drainage, residual dirt, and localized shadows

• Point 4: Track changes by combining power generation data with on-site photographs

• Safety considerations and decision-making when inspecting mounting structures

• Summary: Reassess the causes of low power generation from a structural standpoint

Why Distortion and Tilt of Mounting Racks Lead to Reduced Power Generation

Distortion or tilt of the mounting structure does not necessarily immediately show up as a large drop in power generation. Rather, at first it can appear as small anomalies such as “the output seems a little low,” “it’s underperforming compared to the neighboring block,” or “it doesn’t generate as much as expected on sunny days.” For that reason, in practical work investigating decreases in power generation, the mounting structure tends to be ruled out as a potential cause.

Solar panels’ power output varies depending on the angle and orientation at which they receive sunlight. During design, the tilt angle and orientation are determined according to the conditions of the installation site so the panels are positioned to receive sunlight as efficiently as possible. However, if the mounting rack settles, support posts tilt, or cross rails twist, the angles of the panel surfaces can shift from their original positions. Even small angle differences, if they occur in the same way across multiple panels, can appear as a difference in output for the entire system.

Also, deformation of the mounting structure is not just a matter of angle. If the panel surfaces no longer align and become wavy, the flow of rainwater changes and dirt tends to remain at the lower edges and stepped areas. When dirt concentrates on specific rows or particular edges, it can affect the output of the panels in those locations. Moreover, if the tilt of the mounting structure changes the relative positions between rows, shadows from adjacent rows can extend longer than expected in the mornings, evenings, or during winter. Because the effect of shading varies by time of day and season, it can be difficult to detect from monthly generation figures alone.

Distortion of the mounting frame can be caused by various factors, such as wind and snowfall, ground subsidence, insufficient tightening during installation, scouring around the foundation, loosening of fasteners, and changes in components due to long-term use. Since it is difficult for on-site personnel to judge everything by themselves, it is important to first check whether "its shape has changed compared with before," "the tilt is consistent across each row," and "there are no areas that have settled locally."

When investigating the cause of low power generation, checking only voltage, current, sold electricity, monitoring data, and shutdown history may not lead to the root cause if structural issues remain. The mounting structure is the foundation of the power generation equipment and broadly affects panels, wiring, fasteners, drainage, and shading conditions. To prevent reductions in power output, it is important not to consider the mounting structure as 'something that doesn't change after installation,' but to treat it as an item to be checked periodically for changes.

Point 1: Check how well the panel surfaces align and any changes in tilt angle

The first step in checking for mounting-structure deformation and tilt is to see whether the panel surface is aligned as a whole. When you sight along a row from one end on site, a surface that should be aligned in a straight line can appear wavy or seem to sag in only certain parts. Even if it’s hard to tell from a distance, checking the same row from the side can reveal height differences between support posts or twisting of the horizontal rails.

At facilities with low power generation, it is effective to first separate and observe areas where the decline is noticeable and areas where it is not. For example, if within the same plant only the northern row has low output, only a specific string shows a delayed rise on sunny days, or only a certain block fails to increase output in the afternoon, check whether the racking surfaces in that area share a common tilt or distortion. Rather than simply "looking at the entire racking," inspecting locations in order starting from where the generation data shows anomalies improves the accuracy of the checks.

When checking how well panel surfaces align, it’s important not to rely too much on visual inspection alone. Visual inspection is useful for detecting changes, but impressions can vary depending on the observer’s position, the lighting, and the surrounding terrain. Use an inclinometer, a spirit level, and other measuring instruments on site to record the tilt and elevation differences of each row so that later comparisons are easier. If a high-precision assessment is required, it’s safer to consider having measurements performed by a professional contractor.

Changes in tilt angle do not necessarily occur uniformly across the whole. If the ground has settled in only part of an area, one side of a row may sink, causing the panel surface to become twisted. If there is biased settlement around the base of the posts or foundations, even a visually slight change can impose abnormal forces on the panel mounting points. Because panels are both power-generating components and precision equipment with glass surfaces, prolonged excessive twisting or localized loading should be avoided.

Moreover, tilt of the mounting structure affects not only power generation but also maintainability. If the structure tilts toward the walkway, the risk of contact during work increases, and it can become difficult to inspect wiring and connection points under the panels. Especially when investigating causes of low power output, attention tends to focus on electrical measurements, which can lead workers to approach unstable parts of the mounting. In locations where tilt is suspected, it is important not to climb on or put weight on the structure, but to assess its condition within the range that can be checked from the surrounding area.

If photos taken immediately after installation and records from completion are available, it becomes easier to detect changes by comparing them with the current condition. If you have photos taken from the same direction, height, and distance, you can compare row alignment, panel edge heights, the tilt of support posts, and the ground condition around the foundations. Rather than taking photos for the first time after a drop in power generation occurs, keeping fixed-point photographs during normal operation provides useful reference when investigating the cause.

Point 2: Check for settlement and loosening of foundations, support posts, and fastenings

Deformation or tilt of the mounting structure may not be apparent from looking only at the top panel surface. In fact, changes on the supporting side—such as the foundation, posts, mounting brackets, bolts, nuts, and joints—can show up on the panel surface. When checking structural causes of low power generation, you need to look not only at the appearance of the panel surface but also at the substructure.

On ground-mounted installations, the condition of the soil around the foundations is important. In locations where rainwater flows in, where drainage is poor, near slopes, or where compaction after development may have been insufficient, the ground can settle over time. If only one side of a foundation settles, the support post can tilt slightly, affecting the overall tilt and surface alignment of the racking. If a drop in power output is concentrated in specific rows or sections, inspect the foundations in that area for puddles, soil washout, cracks, depressions, or uneven vegetation.

The tilt of the posts is also an important item to check. A post may look straight at first glance, but its angle can differ when compared with a neighboring post. Viewing several posts in succession makes it easier to tell whether only one is leaning or whether the whole row is tilting in the same direction. If only a single post is abnormal, a local fixing failure or the effect of an external force may be suspected; if the entire row is tilting in the same direction, it can be a sign of changes in the ground or the foundation as a whole.

Loosening of mounting points is an issue whose relationship to a decline in power generation is not obvious. However, when mounting points loosen, panels and racking can move slightly during strong winds, which over the long term can lead to component wear and misalignment. Not only can the panel angle change subtly, but wiring can be put under tension and connection points can be subjected to additional load. If such structural looseness can be detected before it manifests as an electrical fault, it can help prevent reductions in power generation.

However, you should avoid re-tightening bolts or nuts on site indiscriminately. There are appropriate tightening methods and control values, and excessive tightening can damage components. At the inspection stage, observe for obvious looseness, detachment, separation, deformation, rust, contact marks, and abnormal noises, and, if necessary, request confirmation from the construction contractor or maintenance inspection specialists. Even if power generation is low, adjusting structural parts based solely on on-site judgment may actually worsen problems.

When installing on a roof, attention must also be paid to the relationship with the roofing material and the mounting hardware. The points to check vary depending on the roof shape, pitch, substrate, and fastening method. Deflection of the roof surface itself, lifting around the fasteners, changes in the flashing and rainproofing areas, and misalignment of panel rows can all affect the tilt of the mounting structure and its fastening condition. Because inspections on the roof carry a risk of falling, avoid unsafe approaches or working alone, and carry out checks only with safety measures in place.

When inspecting foundations, support posts, and fastenings, it is important not to conclude on the spot that they are the direct cause of reduced power output. For example, even if a tilt is found in a support post, it is premature to assume that this alone is the primary cause of reduced generation. It is necessary to make a judgment in conjunction with solar irradiance conditions, shading, panel soiling, electrical abnormalities, output control, and the status of monitoring data acquisition. What is important is to record whether there are any structural changes and to ensure they can be compared with the generation data.

Point 3: Check for poor drainage, residual dirt, and localized shadows

Distortion or tilt of the mounting structure affects not only the panel angle itself but also the condition of the panel surface. Especially for systems with low power output, it is important to check poor drainage, residual soiling, and localized shading together. Although each of these may seem to have only a small impact individually, when they overlap in the same area they are more likely to appear as a reduction in power generation.

The surface of panels can have some dirt washed away by rain, but when the tilt of the mounting structure changes, the way water flows also changes. If water that should normally run down to the lower edge remains partway or tends to accumulate in a particular corner, mud, pollen, dust, bird droppings, and fine components of fallen leaves are more likely to remain after drying. If there is a band of dirt at the lower edge of the panel, or dirt is concentrated at the same position in the same row, it may not be mere soiling but could be related to a change in the tilt of the mounting structure or drainage.

Dirt residue is a relatively easy-to-detect cause of reduced power output, but it tends to recur unless you verify why dirt remains in that spot. Even if power output temporarily recovers after cleaning, if the tilt of the mounting structure causes water and dirt to continue gathering in the same place, it can lead to another drop in power output. Measures to address reduced power output require not only removing the dirt but also assessing the underlying causes of uneven dirt accumulation.

Local shading can also be related to deformation or tilt of the mounting structure. Row spacing and panel angles are determined at the design stage based on assumed conditions. However, if the mounting structure settles or part of a row tilts, shadows from adjacent rows, railings, fences, vegetation, or nearby equipment can fall more easily than expected during mornings, evenings, or periods of low solar altitude. Because a site can appear unshaded when viewed at a single time during the day, it is important to check during the periods when power generation is low.

When looking at power generation data, pay attention to the daily generation curve. If there is mounting tilt or shading effects, you may see patterns such as a delayed morning ramp-up even on clear days, reduced output only in the morning, a sudden drop only in the afternoon, or similar dips at specific times each day. Of course, these patterns can also be caused by factors other than shading, so they are not conclusive, but they can provide clues for deciding the timing of on-site inspections.

To check for poor drainage, inspecting the site after rain is effective. Puddles, mud splashes, flow marks, eroded soil, and dirt streaks on the lower edges of panels that are not apparent in clear weather become easier to see. However, wet or post-rain sites can be slippery underfoot, and care is required when working around electrical equipment. Prioritize safety during inspections, and, as necessary, focus on areas visible from walkways, photographic records, and observations from a distance.

If the mounting structure's tilt alters the drainage flow, it can lead to scouring around the foundations. Rainwater falling from the panels can concentrate in the same spot and gradually wash away the soil around the base of the support posts, creating a vicious cycle that causes the mounting structure to tilt further. It is important to check drainage flow and ground conditions together—not only to investigate the causes of low power generation but also to prevent future structural risks.

Shadows from vegetation are also an easily overlooked factor. If the mounting structure is tilted so that the bottom edge of a panel is lower, it may be more susceptible to shadowing from grass than usual. Even at sites where mowing is performed, shadows can appear in a short time during periods of rapid growth. In particular, check panels in low positions, the perimeter, along slopes, and around drainage channels to ensure that changes in mounting height are not coinciding with vegetation shadows.

Point 4: Track changes by combining power generation data and on-site photographs

What is important when checking for deformation and tilt of the mounting frame is linking the on-site observations with the power generation data. Even if you feel on-site that "it looks slightly tilted," that alone makes it difficult to judge its relationship to a drop in power output. Conversely, looking at the power generation data alone won’t reveal structural changes. Recording both together makes it easier to narrow down the cause.

First, what you should check is whether the decline in power generation is occurring across the entire facility or is concentrated in specific sections or systems. If it is low overall, you need to broadly check the weather, solar irradiance, output control, measurement data, and any plant-wide shutdowns. If only certain rows, the area connected to a particular power conditioner, or specific strings are underperforming, it is worth focusing on the condition of the racking in that area.

On-site photographs greatly influence the quality of a root-cause investigation. When taking pictures, do not only shoot the suspected abnormal parts up close; photograph the entire row, the relationship with adjacent rows, the alignment of the support posts, the areas around the foundations, the alignment of the panel surfaces, and how shadows fall.

If you only take close-ups, positional relationships become unclear and it becomes difficult to later correlate the images with power generation data. Keeping both wide shots and close-up photos makes it easier to share the situation among stakeholders.

Fixed-point photography is also effective. If you shoot from a different angle each time, it becomes difficult to determine whether differences are due to changes in the mounting structure or differences in shooting conditions. By consciously photographing from the same location, same direction, and same height, it becomes easier to compare the tilt of rows, the angle of support posts, the height at the edges of panels, and uneven dirt accumulation. If low power generation persists, keeping photos at regular intervals—monthly, at each inspection, after rainfall, and after strong winds—will help track changes.

When comparing power generation data, it is important to look not only at daily totals but also at output by time of day. Shadows and angle differences caused by racking tilt can manifest during specific time periods. For example, if output is low only in the morning, check conditions for sunlight from the east and morning shadows. If output is low only in the afternoon, check western-side shadows, inter-row shading, and shadows from nearby equipment. Comparing generation curves on multiple clear-sky days and seeing whether the same pattern occurs at similar times helps focus onsite inspections.

Comparing with adjacent installations or other sections within the same site is also useful. If, under the same weather conditions, only one section has lower power generation, compare equipment capacity, number of panels, connection configuration, tilt angle, orientation, soiling, shading, outage history, and so on. If there are differences in racking tilt or row alignment among these, record them as potential causes. However, be careful not to compare solely on power generation when equipment specifications or connection conditions differ.

When keeping records, it is helpful to consolidate the inspection date, weather, time of inspection, inspection location, photo numbers, the period covered by the power generation data, and any observations so they are easier to use later. Investigations into the causes of low power generation can involve multiple parties. If information becomes scattered among on-site personnel, equipment managers, maintenance personnel, and construction staff, the same checks may be repeated and decision-making can be delayed. Standardizing the record format makes it easier to share the situation and consider countermeasures.

The distortion or tilt of the mounting structure can sometimes change suddenly and significantly overnight, but it can also progress gradually. Therefore, comparing with past records is important, not just a one-time inspection. If you have photos of the initial condition, past inspection records, trends in power output, cleaning history, and inspection logs after strong winds or heavy rain, it becomes easier to infer when changes began. To prevent declines in power output, it is important to keep records of normal conditions rather than only recording after anomalies occur.

Safety Aspects to Watch for and How to Make Decisions When Inspecting Support Frames

When checking racking for deformation or tilt, safety must be the highest priority. Even if you are eager to quickly identify the cause of low power output, you must avoid putting your weight on an unstable rack, stepping on panels, or assuming awkward positions on the roof. Solar power installations are outdoors and involve multiple hazards, including underfoot conditions, wind, rain, slope, and the presence of electrical equipment.

Even for ground-mounted installations, when entering under the mounting structure you need to be careful of overhead components, wiring, fasteners, and uneven footing. In locations where tilting is suspected, components may be more unstable than usual. If you observe conditions such as muddy ground around the foundation, soil erosion, leaning support posts, or deformed fixing points, avoid approaching; take photos from a distance and consider requesting confirmation from a qualified specialist.

On rooftop installations, pay particular attention to fall prevention, stepping through roofing material, slipping, electric shock, and falling objects. Even if it is necessary to go onto the roof to investigate a drop in power generation, inspections should not be performed when safety equipment and work procedures are not in place. Roof-mounted racks may not be assessable solely from what is visible from the ground; however, that is no reason to climb up casually, and it is important to establish an inspection system premised on safety management.

As a procedure for judgment, it is realistic to first check the range and time period of the decline using power generation data, then perform an on-site visual inspection, and, if necessary, proceed to specialized measurements and structural checks. Rather than assuming from the outset that the mounting structure alone is the cause, isolate potential issues including electrical abnormalities, dirt, shading, output control, communication failures, and measurement deviations. If the tilt or deformation of the mounting structure coincides with the trend of reduced power output, prioritize its inspection.

When investigating the causes of low power generation, it is more important to assemble supporting evidence than to rush to decide whether there is an anomaly or not. The condition of the mounting structure becomes clearer by combining photos, measurements, inspection records, and generation data. If you leave the site without recording any oddities you noticed, you will increase the effort required to recheck the same locations later. Even small tilts or uneven soiling, if recorded together with generation data, are useful for ongoing management.

Also, it is important not to treat racking inspections as a one-time task. After heavy rain, typhoons, strong winds, snowfall, earthquakes, changes in drainage on developed land, or nearby construction, the racking may be subjected to loads different from normal. Incorporating inspections not only when you notice reduced power generation but also after such external events helps enable early detection. If the same power plant has previously experienced subsidence or drainage problems, it is advisable to record it as a priority management area.

When distortion or tilt of the mounting structure is detected, it is necessary to consider comprehensively not only the impact on power generation but also structural safety, panel fastening, wiring protection, rainwater drainage, and the feasibility of future operations. Even conditions that appear minor can, if left unaddressed, affect shading, soiling, loads on fastenings, and work safety. Conversely, an apparent visual anomaly is not always the primary cause of a drop in power generation. That is why it is important not to separate on-site inspection and data verification, but to organize them together within the same record.

Summary: Re-examine the causes of low power generation from a structural perspective

To prevent a decline in power generation, it is important to pay attention not only to electrical equipment and monitoring data but also to deformation and tilt of the racking. The racking is not merely a component that supports the panels; it is a fundamental part that affects tilt angle, azimuth, drainage, shading, how dirt accumulates, loads on the fastenings, and the condition of the wiring. If you postpone checking the racking when you notice low power output, you may miss small changes occurring in the structure.

The basic checks are to inspect, in order, the alignment of the panel surfaces, changes in tilt angle, settlement of foundations or supports, looseness of fastenings, poor drainage, remaining dirt, and localized shading. On top of that, combine power generation data with on-site photographs to organize where, when, and how performance declines are occurring. Because judgments tend to be biased if based only on visual inspection, only on numerical data, or only on photographs, the practical point is to review multiple pieces of information together.

Abnormalities in the mounting structure can directly cause a decrease in power generation, or may indirectly affect it through soiling, shading, wiring load, and similar issues. Because such problems often do not immediately present as major faults, recording the normal condition and keeping records that allow you to compare changes can help prevent declines in power output. In particular, it is effective to inspect the mounting structure together with changes in generation data after heavy rain, strong winds, snowfall, earthquakes, or nearby construction.

When you feel that "power generation is low," don't judge solely by the weather or panel soiling; it's important to review the entire installation, including the condition of the mounting structures. If you have a system that can centrally manage on-site inspection records, photos, and generation data, it becomes easier to detect abnormalities early and isolate their causes. To avoid overlooking downward trends in generation and to link on-site inspection findings to subsequent countermeasures, establish operational practices that combine daily generation-data management with records of on-site conditions.