Complete Guide to Increasing Power Generation｜9 Causes of Decline and Countermeasures

Table of Contents

• Increasing power generation begins with identifying the causes of decline

• Cause of decline 1: Viewing power generation data only at a coarse level

• Cause of decline 2: Failing to separate weather, solar irradiance, and seasonal differences

• Cause of decline 3: Neglecting dirt and deposits on the panel surface

• Cause of decline 4: Overlooking shadows from weeds, trees, and structures

• Cause of decline 5: Not noticing abnormalities at the string level

• Cause of decline 6: Not checking for faults in connections and cables

• Cause of decline 7: Missing stoppages or output curtailment of power conversion equipment

• Cause of decline 8: Not reviewing temperature rise and poor ventilation

• Cause of decline 9: Insufficient management of drainage, terrain, and inspection records

• Operational points to sustain power generation improvements

• Summary

Increasing Power Output Starts with Identifying the Causes of Decline

When you want to increase the electricity output of a solar power system, the first thing you need is not to immediately start cleaning or making repairs. Even if you feel that output is low, not rising as expected, or down compared with the same month last year, the cause is not necessarily a single one. Dirt on the panel surface, bird droppings and fallen leaves, shading from weeds or trees, faults in connections, cable damage, shutdowns of power conversion equipment, output curtailment, temperature rise, poor drainage, and insufficient inspection records—multiple factors may overlap to cause reduced generation.

For practitioners searching "how to increase power generation," the important thing is to treat increasing output as an effort to reduce generation losses. In solar power generation, you cannot increase the amount of solar irradiance at the site itself. You cannot increase the number of sunny days, nor change the seasonal solar altitude. However, you can move closer to a state in which the received irradiance is converted into electricity with as little waste as possible. In other words, improving generation output is the work of finding where the power that could be generated is being lost and reducing that waste.

A common mistake when power generation is low is deciding the cause based only on the site's appearance. Cleaning because the panels look dirty, weeding because the grass is overgrown, or suspecting equipment deterioration because the machinery looks old—these judgments are sometimes necessary. However, if the main cause of the generation drop lies elsewhere, carrying out such work will not lead to sufficient improvement. Even if you clean, if morning and evening shading remains, generation is unlikely to recover, and even if you weed, if the power conversion equipment continues to experience short stoppages, daytime generation will not increase.

To increase power generation, it is important to link generation data with on-site conditions to isolate causes. Check when output is low, which equipment is underperforming, whether there is a difference compared to equipment under the same conditions, whether it is low even on sunny days, and whether it becomes unstable after rain. Then, review in order: soiling, shading, connections, equipment, temperature, drainage, and inspection records. Having this sequence clarifies the priorities for cleaning, weeding, repairs, equipment checks, and drainage measures, making it easier to improve generation while reducing unnecessary work.

Cause of Decline 1: Reviewing Power Generation Data at a High Level

The first step to increasing power generation is to view generation data in greater detail. If you only look at monthly or annual generation, you won’t know when, where, or how generation losses are occurring. Even if nothing looks abnormal on a monthly basis, there may be cases where generation drops only during certain hours on sunny days, or where only a specific row, a specific string, or the area connected to a specific conversion device remains at a low level.

Reviewing by time of day makes it easier to discern the likely direction of the cause. If generation is low in the morning, shadows from trees on the east side, slopes, nearby structures, or adjacent equipment may be involved. If it is low in the evening, check for shadows on the west side and the surrounding terrain. If the midday peak does not extend as expected, candidates include dirt on the panel surface, temperature rise, limitations of the conversion equipment, output curtailment, or equipment shutdown. If the generation curve suddenly drops during a sunny day, it is necessary to correlate shutdown logs and alarm logs with the timestamps.

When comparing on an equipment-unit basis, it is important to compare equipment under the same conditions. If you simply compare equipment with different orientation, tilt, number of panels, shading conditions, or connection configurations, you may mistake normal differences for abnormalities. If a specific area is continuously lower compared to adjacent rows or equipment with the same orientation, suspect localized soiling, partial shading, connection faults, cable damage, or anomalies on the power conversion equipment side. Do not judge based only on the overall plant-wide figures; detecting small differences is the shortcut to improving power generation.

Also pay attention to how the power output declines. If it falls suddenly, possible causes include equipment shutdown, wire disconnection, poor connections, or the emergence of obstructions. If it is decreasing gradually, possible causes include accumulation of dirt, growth of weeds or trees, deterioration of on-site conditions due to poor drainage, and aging of equipment or components. For a sudden drop versus a gradual decline, both the locations to check on site and the priority of countermeasures will differ.

As an improvement measure, change operations to use the power-generation curve on clear days as the baseline and to check generation by time of day and by individual equipment units. By narrowing down the time periods and equipment scope where declines appear before going to the site, you can reduce unnecessary inspections. Rather than wandering aimlessly around a large plant, focusing inspections on locations showing generation declines makes it easier to find the causes that lead to generation improvements more quickly.

Cause of decline 2: Not separating weather, solar radiation conditions, and seasonal variations

When you feel that power generation is low, what you should check before suspecting an equipment fault are the weather, solar irradiance conditions, and seasonal variations. Solar power generation is greatly affected by the amount of sunlight, so output will drop during periods with many cloudy or rainy days even if there is no problem with the equipment. If you compare only monthly generation with the same month in the previous year or with the previous month and immediately conclude there is an equipment failure, the main cause may actually be differences in the weather.

On the other hand, you must avoid overlooking real anomalies by attributing them to the weather. If the entire plant is declining uniformly in line with regional weather, the impact of solar irradiation conditions is likely significant. However, if only part of the plant is lower while other equipment in the same plant is operating normally, or there is a clear difference compared with equipment under similar conditions, weather alone cannot explain it. In such cases, it is necessary to check for on-site causes such as soiling, shading, poor connections, equipment shutdowns, or output curtailment.

To distinguish between weather-related and equipment-related causes, it is effective to compare clear days with other clear days or days with similar weather. On cloudy or rainy days, power generation fluctuates greatly, making it difficult to discern the characteristics of anomalies. By selecting and inspecting generation curves from clear days, it becomes easier to identify effects such as shadows that fall at the same time each day, string anomalies that result in lower output only on specific equipment, and equipment shutdowns that occur only for certain periods.

Seasonal differences are also an important factor to consider. In winter the sun’s elevation is lower, and shadows from nearby trees and terrain tend to be longer. In summer, although solar radiation is stronger, panel temperatures and temperatures around equipment rise, which can make it harder for output to increase. During rainy seasons, monthly power generation tends to be lower, and after strong winds or heavy rain attention is needed for fallen leaves, sediment, deposits, poor drainage, and the condition around cables.

As a countermeasure, rather than judging based only on days with low generation, check the weather, solar irradiance, season, and the difference compared to equipment under the same conditions together. By distinguishing whether the decline is a natural decrease due to weather or a generation loss that can be improved on-site, you are less likely to misprioritize cleaning or repairs. To increase generation, it is important to understand natural variability and then focus on on-site inefficiencies that can be improved.

Cause of performance degradation 3: Leaving dirt and deposits on the panel surface untreated

Dirt and deposits on the panel surface are a common cause of reduced power output. Because solar panels generate electricity by receiving sunlight at their surface, dirt on the surface reduces the light reaching the cells. The type of soiling varies with site conditions and includes soil dust, pollen, yellow sand, bird droppings, fallen leaves, sap, dust from nearby construction, road-derived dust, and salt-containing deposits that tend to adhere in coastal areas. Even light soiling spread over a wide area can affect power generation, and localized deposits can act as strong shading even over a small area.

Particularly noteworthy are the band-like stains that remain along the lower edges of panels and around the frames. It is often assumed that rain will wash them away naturally, but in reality the flow of rainwater can collect the dirt at the bottom edges and leave it there. On panels with a gentle tilt, water does not drain well and dirt tends to accumulate. Even dirt that is not noticeable from a distance can affect power generation if it covers part of a cell.

Localized deposits such as bird droppings and fallen leaves should not be overlooked. Unlike dirt that spreads thinly across the entire surface, these cover specific areas densely and create partial shading that impedes power generation. If only certain installations show low power output, focus on checking the panel surfaces around those installations. Rows near trees, around structures where birds tend to perch, rows that are often downwind, and areas near unpaved walkways are more likely to accumulate dirt and deposits.

As an improvement measure, determine cleaning targets starting with locations that have the greatest impact on power output. Rather than cleaning all panels at the same frequency, focus on systems where a decline in power output has been observed, rows with concentrated soiling, areas where soiling is noticeable along the lower edge, and spots with heavy bird-related fouling or abundant fallen leaves. By comparing photos and power output before and after cleaning, it becomes easier to judge how much the soiling at that site had affected power output.

However, cleaning must be carried out so as not to damage the equipment. Avoid scrubbing hard with rigid tools, performing sudden work during times when the panels are at high temperatures, or working without confirming the electrical safety of the equipment. Cleaning to increase power generation is not a cosmetic task to improve appearance, but a maintenance operation to restore the panels' light-receiving condition and to keep the equipment operating stably over the long term. By recording the locations and extent of soiling and the likely causes, you can use that information for future inspections.

Cause of Decline 4: Overlooking Shadows Cast by Weeds, Trees, and Structures

One thing you must always check when trying to increase power generation is the effect of shading. Because solar panels generate power from sunlight, even a shadow on part of a panel can reduce its output. Causes of shading include weeds, trees, fences, utility poles, surrounding buildings, mounting racks, adjacent panel rows, monitoring equipment, and others. Shadows move with the time of day and the seasons, so the fact that you did not see any shading at the time of inspection does not necessarily mean there is no problem.

Weeds are a common cause of on-site generation losses. Even if they cause no problems in winter or immediately after installation, they can grow rapidly from spring through summer and cast shadows on the lower edges of panels and on the front rows. Even when weeds do not touch the panels, the low sun angles in the morning and evening lengthen shadows. Furthermore, when weeds become dense, airflow worsens, inspection walkways become blocked, and it becomes difficult to check around equipment. Because they affect not only power output but also maintainability and safety, weed management is fundamental to improving power output.

Shading from trees is a factor that can become problematic during long-term operation. Even trees that had little impact at the time of installation can grow over several years and reduce power generation. Trees on the south, east, and west sides in particular cast shadows on the panels depending on the time of day. At solar plants near forests or slopes, the elevation of the terrain and the height of the trees can combine to produce long shadows in winter. If power generation is low only in winter, or if there are large drops in the morning and evening, it is necessary to check both the trees and the terrain.

As a countermeasure, inspect the site at the times when power generation data shows a decline. If output is low in the morning, check the site in the morning; if it is low in the evening, look for shadows in the evening. Even if there is no problem at noon, large shadows can appear in the morning or evening. Also, even if there is no problem in summer, shadows can lengthen in seasons when the sun’s altitude is lower. When you find a shadow, record the time it occurs, the source of the shadow, the equipment affected, and take photographs.

Care should also be taken regarding shadows from surrounding structures and additional equipment. Adding new equipment within the power plant, or installing fences, signs, or monitoring poles, can cast shadows at certain times of day. To increase power generation, it is important not only to reduce existing shading but also to operate in ways that avoid creating new shading. Shadow management does not end with a single weed removal; it needs to be continued while monitoring seasonal changes.

Cause of Decline 5: Not Noticing Abnormalities at the String Level

The causes of low power generation do not necessarily appear uniformly across the entire power plant. Even if the total power output does not look significantly abnormal, only some strings may have reduced output. Such partial generation losses can be hard to notice in the monthly total, but if they continue over a long period they can lead to substantial losses. To increase power generation, it is important not to be reassured by the overall average and to check for differences at the string level.

When checking for anomalies at the string level, compare strings that are under the same conditions. If you simply compare those that differ in panel count, orientation, tilt, shading conditions, or connection configuration, you may mistakenly judge normal differences as anomalies. Check whether any string is consistently lower compared with adjacent rows or equipment with the same orientation. If only a specific string is low, candidates include soiling, partial shading, poor connections, cable damage, or equipment-side problems.

Pay attention to how anomalies appear. If output is consistently lower than the surroundings even on sunny days, contamination or connection problems are suspected. If it is lower only in the morning and evening, check for the effects of shading. If anomalies tend to appear after rain, moisture ingress or the condition of connection points may be involved. If it becomes unstable during periods of high temperature, poor contact or the temperature environment around the equipment are also possible causes. Combining the power output waveform with on-site conditions makes it easier to narrow down the cause.

As a corrective measure, establish management that allows suspected abnormal locations to be identified accurately on site. At sites where equipment numbers or row numbers are hard to understand, even if an anomaly is found in the data it can take time to find the corresponding location in the field. A photo alone may not convey the location. For improving power generation, being able to share the exact location among stakeholders is as important as finding the anomaly.

Even small differences in power generation can become a large loss if they persist every day. In particular, when poor connections or cable damage are involved, it can lead not only to reduced power output but also to safety risks. To increase power generation, it is important not to judge only by the overall numbers, but to detect detailed anomalies early and connect them to necessary inspections.

Cause of degradation 6: Not checking connectors and cables for faults

Even if solar panels are receiving sunlight normally, defects in connections or cables can prevent the generated electricity from being fully extracted. Loose terminals, poor contact, damage to cable insulation, moisture ingress, animal damage, damage during mowing operations, and age-related deterioration are important causes of reduced power generation. These can be difficult to detect from appearance alone, so it is necessary to assess them by combining power generation data with on-site conditions.

You should suspect faults in connectors or cables when only certain installations show low power output, when abnormalities tend to occur after rain, when power generation suddenly drops, or when the output fluctuates unstably. If only part of the system is underperforming despite no visible dirt or shading, electrical faults should also be considered. When there is a persistent difference compared with a string under the same conditions, prioritize checking the connectors and cables.

Cables are particularly susceptible to on-site environmental conditions. In areas with heavy weed growth, it becomes difficult to check the condition of cables. In locations with poor drainage, moisture and standing water can affect the connection points. On sites that are easily accessed by animals, cable damage can also occur. To improve power generation, it is essential not only to carry out repairs but also to check the site conditions that could lead to recurrence.

As corrective measures, organize the equipment showing abnormalities, the time of occurrence, changes in power generation, on-site photos, and the surrounding environment, and, if necessary, connect these to a professional inspection. Even if you want to increase power generation, on-site personnel should avoid attempting to judge by forcibly touching connection points or the internal parts of equipment. When checking electrical equipment, prioritize safety above all and respond only after clearly identifying the basis for suspecting an abnormality.

If you overlook problems with connection points or cables, power generation may not recover even after cleaning or weeding. Even if visible issues are resolved, generation losses will continue if faults remain in the paths that carry electricity. When considering how to increase power output, it’s necessary to check not only the light-receiving surface but also the parts that support the flow of electricity.

Cause of decline 7: Overlooking inverter shutdowns and output curtailment

The causes of low power generation are not limited to the panels and wiring. If the equipment that converts the generated electricity is stopped or its output is being limited, power generation will not increase even when solar irradiation is sufficient. To raise generation, it is essential to check the operating status of the power conversion equipment, shutdown history, alarm history, and whether output curtailment is in effect.

When reviewing stoppage history, check which equipment stopped, when it stopped, and for how long. Even a short stoppage can cause large losses if it occurs during daytime when generation is high. If stops and restarts are repeating during the day, they may not stand out in the monthly totals but can still result in missed generation. Whether only a specific piece of equipment stops or multiple pieces stop at the same time will change which causes you should suspect.

If output curtailment is occurring, power generation may plateau even on clear days. If the upper part of the generation curve appears flat, check operational information and historical data. However, a flat curve does not necessarily indicate curtailment. Similar shapes can result from equipment capacity limits, temperature rise, soiling, shading, or measurement anomalies. Do not judge based on the generation curve alone; it is important to verify equipment records together with on-site conditions.

As a countermeasure, cross-check the time of the drop in power generation against the equipment history. If the time the generation fell coincides with the time of alarms or shutdowns, it becomes easier to narrow down the possible causes. If there are no anomalies in the equipment records, check other causes such as panels, wiring, shading, soiling, and solar irradiance conditions. Addressing issues based on data and historical records rather than on conjecture is the key to preventing failed remediation.

We also check the environment around the equipment. If ventilation is poor due to grass or accumulated debris, the surroundings are hard to see making inspections difficult, or heat tends to build up, these conditions may affect the operating environment. To increase power generation, it is important not only to address the conversion equipment itself but also to review the surrounding environment so the equipment can operate stably.

Cause of degradation 8: Not re-examining temperature rise and poor ventilation

A frequently overlooked cause of reduced power output is rising temperatures and poor ventilation. Solar power generation generally produces more electricity with stronger sunlight, but when panel temperatures or the temperatures around equipment rise, output can become suppressed. If generation on a clear summer day does not reach expected levels, you should check the thermal environment as well as the solar irradiance.

Panels are exposed to strong sunlight outdoors, so their surface temperature rises. If the surrounding ventilation is poor or weeds are growing thickly under the panels, heat can become trapped. Temperature-related output decreases may not appear as a sudden shutdown but as a slowdown in the increase of power generation. Especially at sites where power generation tends to level off around noon in summer, it is worth checking the ventilation conditions.

Conversion equipment is also affected by temperature. If grass or other objects around the equipment obstruct heat dissipation, it can lead to reduced efficiency or trigger protective operations. The area around the equipment should be kept accessible for inspection, allow airflow, and be arranged so that any abnormalities can be checked immediately. Conditions in which weeds or accumulated debris make the area around the equipment hard to see are undesirable not only for power generation but also in terms of inspectability and safety.

As a countermeasure, carry out management to reduce unnecessary heat buildup. Controlling weeds under the panels, ensuring ventilation around equipment, maintaining clear inspection walkways, and checking for dust and deposits are measures that can be implemented on site. While it is not possible to completely eliminate temperature increases themselves, power generation losses caused by poor ventilation or inadequate management around equipment can be reduced.

Consider seasonal differences as well. If power generation falls short of expectations only in summer, temperature and ventilation effects are likely candidates. If it is low only in winter, check for the decrease in solar altitude, shading, and the influence of surrounding terrain. Methods to increase generation are not the same year‑round. It is important to adjust the inspection items on the assumption that the causes of reduced generation change with the seasons.

Cause of Deterioration 9: Insufficient Management of Drainage, Topography, and Inspection Records

When investigating the causes of reduced power generation, it is necessary to check not only the panels and equipment but also the plant-wide drainage, topography, and inspection routes. Locations where water tends to accumulate, places where sediment can flow in, pathways prone to becoming muddy, slope failures, erosion around mounting structures, and areas where cables are likely to become exposed can directly or indirectly cause reductions in power output. These are important factors that lead to soiling, weed growth, connection faults, and deteriorated inspectability.

In areas where puddles remain after rain, weeds tend to grow more easily. When weeds grow, they cast shadows, reduce airflow, and make inspections more difficult. Muddy walkways can slow work and may lower the frequency of cleaning and weeding. In places where sediment washes in, it can accumulate under panels and around cables, causing soiling and damage. If cleaning and weeding do not prevent problems from recurring in the same locations, drainage or topography issues should be suspected.

When inspecting topography and drainage, on-site checks after rain as well as in fine weather are effective. Identify where water flows in, where it pools, and where it drains away. Recording puddles, sediment buildup, vegetation overgrowth, pathway subsidence, and changes to slopes will reveal locations that are likely to recur. If poor drainage is left unaddressed, dirt and weeds will reappear, resulting in the same power-generation losses occurring repeatedly.

Inspection records are also important for identifying causes of recurrence. If you can confirm whether the same location has shown dirt in the past, whether grass has been growing in the same row, or whether the same equipment has experienced stoppages, you can narrow down the possible causes more quickly. If records are insufficient, start from this inspection to record photos, date and time, equipment number, location, details of abnormalities, and the status of responses so they can be used for the next check.

As a countermeasure, consider drainage, topography, inspection routes, and inspection records as part of efforts to improve power output. Don’t just clean dirt; verify why that spot becomes dirty easily. Don’t just mow grass; examine why grass tends to grow in that area. Don’t just repair connection points; check background factors such as moisture, drainage, and exposed cables. Adopting this perspective makes it easier to maintain the effects of power output improvements over the long term.

Operational Points for Sustaining Power Generation Improvements

Efforts to increase power generation cannot be completed with a single cleaning or repair.

A solar power plant is an outdoor facility, and its condition changes with the seasons, weather, the surrounding environment, and equipment aging. Even if cleaned, dirt returns; even if weeds are removed, grass grows; trees mature; and equipment and wiring change condition during long-term operation. To achieve stable improvements in power generation, a system for continuous inspections and countermeasures is necessary.

First, the important thing is to compare power generation before and after the measures. After performing cleaning, weeding, repairs, equipment checks, and drainage checks, confirm how the power generation has changed. It is difficult to completely eliminate the influence of weather, but by comparing sunny days with each other or comparing installations under the same conditions, you can grasp certain trends. Prioritize measures that produced large effects for future work, and if effects are hard to see, suspect other causes.

Next, keep locations that are prone to recurring problems as management targets. If you record rows that easily accumulate dirt, time periods when shadows are likely to occur, spots where water pools, sections of aisles that are prone to deterioration, and equipment that is likely to show abnormalities, you can check them before power generation drops significantly. To steadily increase power generation, it is important not only to respond after generation has dropped but also to identify conditions that tend to cause drops in advance and take countermeasures.

When multiple people are responsible for management, it is also important to be able to share the exact location. In large power plants, similar rows and pieces of equipment are arranged, so photos alone can make it difficult to identify the location. If equipment numbers, location information, photos, and work history are recorded together, on-site staff, management personnel, inspection personnel, and repair personnel can more easily confirm the same location. Improving power generation output is also about creating a system that uses observations made on site to inform the next improvements.

It is also important to clarify the priorities for improving power generation. Trying to solve all issues at once can create a large workload and cause measures with the greatest impact on generation to be deferred. Prioritize inspection of equipment that shows a clear decline in generation data, shadows that have a long duration of impact, recurring soiling or drainage failures, and devices that experience frequent short-duration stoppages. To increase power generation, it is practical to implement countermeasures in sequence, starting with the areas that have the largest generation losses.

Summary

When organizing a complete guide to increasing power generation, the important thing is to identify the causes of generation loss in order and make improvements starting with the areas that have the greatest impact on output. In solar power generation, you cannot increase the solar irradiance itself at the site. However, you can improve output by bringing the system closer to a state that converts received solar irradiance into electricity without waste. To do that, you need to check, in order, power generation data, weather and irradiance conditions, panel surface soiling, shading from weeds or trees, abnormalities at the string level, connections and cables, power conversion equipment, temperature environment, drainage, and inspection records.

When you notice that power generation is low, rather than immediately performing cleaning or repairs, it is important to first break down and review the data. Identify when output is low, which equipment is underperforming, and whether there are differences compared with equipment under the same conditions. With that information in hand, an on-site inspection will clarify where cleaning is needed, the extent of weed removal required, which connection points should be inspected, which devices should be checked, and which drainage or access routes should be reconsidered. When improving power generation, it is crucial to make decisions based on data and on-site conditions, not on impressions.

Also, efforts to increase power generation are not something that can be completed in a single operation. Even if you clean, dirt will accumulate again; even if you remove weeds, grass will grow back; trees will grow; and equipment and wiring will change condition with age. By comparing power generation before and after countermeasures, keeping on-site photos and work records, and using them for the next inspection, the accuracy of improvements will increase. To raise power generation stably, it is essential not only to remove the causes but also to create a site environment and management system that make the same causes less likely to occur.

In particularly large power plants, a system for accurately sharing problem locations is important. If you record dirty-prone rows, locations where shadows occur, places where water accumulates, anomalous strings, repair locations, cleaning areas, and inspection photos together with location information, stakeholders can more easily confirm the same spots. By combining power generation data with on-site location information, it becomes easier to explain priorities for cleaning, weeding, and repairs, and to streamline recurrence checks for future inspections.

If you want to continuously pursue ways to increase power generation — from identifying causes of reduced output to implementing improvement measures — based on field data, using LRTK is also effective. As an iPhone-mounted high-precision GNSS positioning device, LRTK is useful for recording inspection locations within solar power plants, areas prone to soiling, shadow occurrence points, poor drainage locations, abnormal equipment, repair locations, cleaning ranges, and on-site photos together with high-precision positional information. By recording the results of checking the nine causes of reduced output with location information, it becomes easier to advance power generation improvements based on field data rather than on intuition.