8 Measures to Increase Solar Power Output｜Check Cleaning, Tilt, and Shading

When aiming to increase solar power generation, the first thing to check is not “adding equipment” but whether the existing system is operating close to its intended generation performance. Generation output varies due to multiple factors: solar irradiance, panel orientation and tilt angle, shading, soiling, wiring, equipment condition, inspection frequency, and how generation data is analyzed. A single measure may yield noticeable improvement in some cases, but at many sites small degradation factors accumulate, making it difficult for output to reach expected levels.

In this article, aimed at practitioners searching for "how to increase power generation", we organize eight measures to check for increasing photovoltaic power generation from the perspectives of cleaning, tilt/angle, shading, inspection, and operational management. Rather than impractical modifications or poorly substantiated improvements, we focus on and explain only measures that are easy to verify on site and useful as decision-making information.

Table of Contents

• Before increasing power generation, isolate the causes of the decline

• Measure 1 Check the panel surface for dirt and establish a cleaning plan

• Measure 2 Identify where and when shading occurs

• Measure 3 Verify panel tilt and orientation to match site conditions

• Measure 4 Prevent loss of sunlight caused by weeds and nearby obstructions

• Measure 5 Compare generation data daily, monthly, and by system

• Measure 6 Detect abnormalities in power conditioners and wiring early

• Measure 7 Keep continuous records of inspections and maintenance

• Measure 8 Set priorities for improvement measures and implement them in a manageable way

• Summary To increase power generation, combine on-site inspections and data management

Identify the causes of a decline in power generation before increasing output

To increase the power output of a solar power system, it is important to first isolate what is causing the output to be low. Because generation is heavily influenced by the weather, if output is low on just one day you cannot judge that the equipment is malfunctioning based on that alone. There will always be variations due to natural conditions such as cloudiness, rain, snowfall, yellow sand (Asian dust), rising temperatures, and seasons with low solar irradiance.

On the other hand, if clear weather persists but power generation is clearly lower than in the same month of the previous year or on days with the same conditions, if only some circuits within the same site have low power generation, if cleaning does not improve it, or if output drops only during specific time periods, there may be some factor on site causing the decline. Measures to increase power generation begin by carefully checking for these kinds of differences.

When considering how to increase power generation, be careful not to judge based only on short-term generation figures. Solar power generation experiences significant month-to-month variation even with the same equipment because solar altitude and sunlight hours change with the seasons. In summer, although sunlight hours are longer, increased panel temperatures can reduce output. In winter, lower ambient temperatures can be advantageous for panel output, but generation is affected by shorter sunlight hours, lower solar altitude, and snowfall. Therefore, it is necessary to combine multiple perspectives: not just day-over-day comparisons, but year-on-year same-month comparisons, comparisons with days of similar weather, and comparisons between systems within the installation.

Additionally, measures to increase power output include those that are easy to implement immediately and those that require inspection by specialist contractors. Visual checks around the panels, the extent of weed growth, how shadows fall, and comparison of generation data are relatively easy checks for site managers to undertake. On the other hand, internal inspections of electrical equipment, verification of insulation condition, equipment replacement, and wiring refurbishment carry risks of electric shock or equipment shutdown, so they should be entrusted to maintenance personnel familiar with electrical systems or to qualified professionals.

Taken at face value, the phrase "increase power generation" tends to prompt the idea of adding equipment. However, in practice the basic approach is to first reduce the factors that cause declines and bring generation closer to the level it should achieve. By checking dirt, shading, equipment malfunctions, insufficient record-keeping, and delayed inspections one by one, you can more easily target stable power generation while avoiding unnecessary additional investment.

Measure 1: Inspect the panel surface for dirt and develop a cleaning plan

If the surface of solar panels is dirty, the light reaching the panels can be blocked, which may lead to reduced power generation. The causes of dirt are varied: sand and dust, yellow dust, pollen, bird droppings, fallen leaves, deposits from exhaust, coastal salt, dust from nearby construction, and other sources. Some dirt can be washed away by rain to a certain extent, but stubborn grime and dirt that accumulates along the bottom edge of the panels may remain.

What you should pay particular attention to is when dirt is concentrated on some cells or some panels. Because solar panels are composed of multiple cells, modules, and strings, localized soiling can affect the output of the circuit. You should check not only cases where the entire surface is lightly soiled, but also localized obstructions of sunlight such as bird droppings or fallen leaves. Even small-looking spots of dirt can cause a decrease in power generation depending on where and when they occur.

When creating a cleaning plan, it is important to identify the seasons and locations prone to soiling rather than blindly increasing cleaning frequency. In early spring there is pollen and yellow sand, during dry periods there is sand dust, and if land development or agricultural work is taking place nearby you are more likely to be affected by airborne particulate matter. Recording the trends of soiling in places where birds tend to gather, near trees, along roadsides, and close to the coast also makes cleaning decisions easier.

While cleaning can help improve power generation, if performed incorrectly it can scratch panel surfaces, damage mounting structures or wiring, or lead to worker falls. Avoid actions such as vigorously scrubbing with hard tools, suddenly applying cold water when temperatures are high, or carelessly spraying electrical equipment with water. For rooftop or high-elevation installations, ensuring safety takes priority over the cleaning itself. Do not force doing it in-house; it is important to confirm a method that suits the equipment conditions.

After cleaning, record the date performed, the scope, the type of soiling, the weather, and the power output before and after cleaning. If the power output does not change despite cleaning, there may be factors other than soiling. Conversely, if an improvement is observed after cleaning under similar solar irradiance conditions, the soiling was likely the main cause of the power decrease. In this way, do not treat cleaning as a one-off task; evaluate it together with the data so you can use it to inform future maintenance planning.

Countermeasure 2: Identify where and when shadows occur

Checking for shadows is extremely important for increasing power output in solar power generation. Because solar panels generate electricity by receiving sunlight, shadows from buildings, utility poles, trees, fences, signs, adjacent equipment, snow accumulation, weeds, and other sources can reduce generation during those times. Shadows do not appear in the same place all day; they move with the seasons and time of day, so it is important to be aware that they can be easily overlooked depending on the timing of on-site inspections.

A troublesome aspect of shading is that it doesn’t affect the entire installation uniformly, but rather only some panels or certain rows. Because generation systems are made up of multiple panels and circuits, partial shading can affect the output of a string or a power conditioner unit. Even if you think the shading only occurs in the morning and evening, over the course of a year it can produce a non-negligible difference in energy generation.

When checking shadows, walk the site on a clear day and record which rows receive shade at which times. Checking several times — in the morning, around midday, and in the afternoon — makes it easier to grasp how the shadows move. Also, because the sun’s elevation differs between summer and winter, there are places where shadows extend only in winter. Even if there are no problems during summer inspections, the low solar altitude in winter can cause shadows from buildings and trees to have a large impact.

If the cause of shading is trees or weeds, pruning or weeding may improve the situation. For objects that are difficult to remove, such as buildings or utility poles, it is necessary to determine the extent of the shading and reflect that in the evaluation of power generation data. When installing new nearby equipment, it is also important to check in advance whether it will create shadows in the future. Even when adding equipment, placing it so that it casts shadows on existing panels may prevent the overall expected power generation from being achieved.

Checking for shading is effective not only by visual inspection but also by cross-referencing with generation data. If there are patterns such as output dropping only during specific time periods, an unnatural dip in the graph on sunny days, or a section being lower compared with other systems of the same capacity, these can be indicators of shading. If the shadows observed on-site match the output drops seen in the data, it becomes easier to prioritize countermeasures.

Measure 3: Verify panel angle and orientation to match site conditions

Solar power generation output varies with the panels’ tilt angle and azimuth. In general, the closer the orientation and tilt are to those that efficiently receive solar radiation, the easier it is to obtain higher generation. However, the desirable angle varies depending on the region, installation site, roof shape, land constraints, surrounding shading, mounting structure, wind loads, and snow conditions. Therefore, you should avoid the simplistic idea that simply increasing the angle is better or that the same direction is always optimal.

If you want to increase the power generation of an existing installation, the first thing to check is whether the assumptions made at the design stage still match the current conditions. Racking tilt, loosened fastenings, ground subsidence, deformation from snow or wind, or orientation errors during installation can cause discrepancies between the expected generation in the design and the actual generation. For ground-mounted systems, it is important to check that there is no variation in tilt and height between racking rows. For rooftop installations, you need to consider roof pitch and orientation constraints and examine factors including how shadows and soiling accumulate.

When determining the angle, consider not only power generation but also how easily rainwater can naturally clean the panels. On installations with a small tilt, dirt may not wash off easily and tends to remain at the lower edge of the panels. Conversely, increasing the tilt can make them more susceptible to wind effects, and unless row spacing is widened, shadows from the front row may fall on the rear rows. Therefore, the angle should be considered in terms of a balance among power generation efficiency, structural integrity, safety, maintenance, and land use.

Changing the angle or orientation of existing equipment is not a simple task. Because it involves the racking structure and methods of attachment, making changes based on on-site judgment alone can affect safety in high winds, roof waterproofing, and cable routing. It may also be necessary to verify consistency with design documents, equipment certifications, contract terms, and interconnection requirements with the utility. When reviewing angles to improve power generation, it is important to confirm on-site measurements, design conditions, and structural conditions before making a professional judgment.

During the planning stage for new installations or renovations, consider not only maximizing power output but also year‑round stability. If decisions are based only on generation in summer, winter, or at noon, actual operation may yield results that differ from expectations. By examining monthly generation, shading, ease of cleaning, and maintenance access routes, you can move toward a layout that is more likely to increase power output.

Measure 4: Prevent reduction of solar radiation caused by weeds and surrounding obstacles

In ground-mounted solar power installations, weed management can affect power generation. When vegetation grows tall and reaches the lower edge or front of the panels, it shades them and reduces power output. Especially with low-mounted racks, on slopes, in areas where rainwater tends to collect, or where seeds are easily blown in from the surroundings, vegetation can grow quickly in a short period. Rather than increasing generation, weed control is indispensable as a basic maintenance measure to prevent declines in power output.

The impact of weeds varies by time of day more than it appears. Even if shadows are not noticeable at noon, in the morning and evening grass shadows can extend and fall on the panels. Also, in summer grass grows rapidly, and if inspection intervals are long, by the next inspection it may be more overgrown than expected. In power generation data, this can appear as reduced output only during certain hours despite sunny conditions, or as differences between systems.

When performing weed control, a work plan is necessary to avoid damaging panels, wiring, and mounting structures. You must prevent damage to panels from stones thrown by a brush cutter or from cutting wiring. When implementing weed-prevention measures, you also need to consider drainage, ground conditions, the scope of work, and future inspection routes. If using herbicides, confirm they are appropriate for the surrounding environment, drainage, neighboring land, and equipment management rules. If the sole purpose is simply to remove vegetation, it can affect stormwater management and slope protection, so it is important to consider it as part of overall site management.

In addition to weeds, nearby obstacles can affect power generation. Temporary materials, stored items, vehicles, signs, added fences, nearby buildings, and overgrown trees—things that were not present at the time of installation—may cast shadows. On site, we check not only the equipment itself but also changes around the site. Especially for equipment operated over long periods, the surrounding environment changes gradually, so periodic reviews are necessary.

Management of weeds and obstructions as a measure to increase power generation is often underestimated because it involves work in the visible area. However, even if there are no electrical faults, power generation will not improve if sunlight is being blocked. Before considering complex equipment replacements, first confirming that sufficient light reaches the panels is the practical shortcut in the field.

Countermeasure 5: Compare power generation data by day, by month, and by grid

To increase power generation, it is necessary not only to inspect the site but also to continuously check generation data. In solar power generation, fluctuations in solar irradiance and weather are large, so simply looking at “less today” or “more this month” is not sufficient to determine the cause. By comparing across multiple units—daily, monthly, year-on-year for the same month, or by system within the same site—you can more easily identify factors causing declines.

For daily data, the power generation curve on clear-sky days is important. On sunny days, output typically rises toward daytime, becomes high around midday, and then falls toward the evening. If there is an unnatural dip in this curve, it can be a clue to suspect shading, equipment control, faults, communication anomalies, or grid-side constraints. Because cloudy days fluctuate greatly with cloud movement, comparing with clear-sky days is more suitable for anomaly detection.

For monthly data, check for seasonal trends. By comparing the power generation for the same month each year, you can grasp long-term declines while accounting for weather variations. Even if generation is lower than in the same month of the previous year, the solar irradiation conditions that month may have been poor. Therefore, if possible, also check solar irradiation, downtime, whether output curtailment occurred, and maintenance/inspection history to make assessment easier.

Comparing by system is also effective. If a system with the same capacity, same orientation, and the same conditions shows reduced power generation only in part, there may be a problem specific to that system. Focus on checking how shadows fall, panel soiling, wiring, connection points, and the condition of equipment. If you only look at the power generation of the entire installation, localized declines can be masked by the overall output. Looking at each system makes it easier to narrow down the areas of decline.

When checking data, what you need to be careful about is the reliability of the measurements themselves. Communication failures or faults in measurement instruments can make the data appear low even when power is actually being generated. Conversely, if you trust only the displayed values and skip on-site verification, you may miss actual problems. Data management aimed at increasing power generation should not be based solely on the numbers; it is important to make judgments by cross-checking them with on-site conditions.

Measure 6: Early detection of abnormalities in power conditioners and wiring

The causes of reduced power output in solar PV systems are not limited to the panel surface or shading. Malfunctions on the electrical equipment side can also prevent the generated electricity from being fully extracted. Abnormalities in power conditioners, junction boxes, wiring, terminals, breakers, monitoring equipment, and the like can lead to reduced or halted power generation, so early detection is important.

A power conditioner is an important device that converts the direct current power generated by solar panels into alternating current power and controls operating conditions. If this device is stopped, showing errors, limiting output due to a rise in temperature, poorly ventilated, or has dirty filters or air vents, the amount of power generated may be less than it should be. Regularly check the indicator lamps, error history, and operating status, and record and respond to any abnormalities.

Faults in wiring and connection points can also cause reduced power generation. Poor connections, damaged cables, loose terminals, water ingress, animal damage, and deterioration from aging not only reduce generation efficiency but also create safety risks. However, internal inspection and measurement of electrical equipment involve hazards. Because they can lead to electric shock, short circuits, or fires, personnel without specialized knowledge should not handle electrical equipment carelessly.

As initial checks that operational staff can easily perform, look for visual abnormalities, unusual noises, unusual odors, abnormal heating, warning indications, shutdown history, surrounding ventilation conditions, signs of rainwater intrusion, and traces of animal damage. If any of these are found, record photographs and the date and time, and inform a specialist contractor of the situation. Organizing when the drop in power generation began, which system it is occurring in, and the time periods when errors occurred will make it easier to proceed with a root-cause investigation.

Also, even if part of an installation is offline, it can be hard to notice if you only look at total power generation. In installations with multiple power conditioners, it is effective to check the generation and operating status of each unit. Trends such as only one unit having low generation, a unit shutting down at specific times, or output capping even on sunny days can provide clues for identifying what to improve.

Countermeasure 7: Continuously keep records of inspections and maintenance

Efforts to increase power generation cannot be completed with a single inspection or cleaning. Solar power generation equipment is designed for long-term operation, and its condition changes with the seasons, weather, the surrounding environment, and the aging of components. For that reason, to stabilize power generation, it is important to continuously keep records of inspections and maintenance.

Items to record include the inspection date, weather, inspector, panel soiling, shading conditions, weed condition, equipment readings, the presence or absence of abnormalities, details of cleaning and weeding carried out, photos, and changes in power output. It is important that the records make the situation clear when reviewed later, even if they are not in a special format. Without records, when power output decreases it becomes difficult to determine when the abnormality began, whether the same trend occurred in the past, or whether cleaning or inspection led to improvement.

Photographic records, in particular, are useful for site management. Dirt on panel surfaces, the way shadows fall, the height of weeds, and the condition around equipment can be difficult to convey in writing alone. If you take photos regularly from the same position and in the same direction, changes become easier to see. When power output declines, comparing with past photos can sometimes reveal an increase in soiling or obstructions.

Maintenance records are important when personnel change. In managing solar power generation facilities, relying on a predecessor’s experience and memory can result in loss of information during handover. If you document which locations tend to get dirty, which seasons weeds grow easily, and which equipment has shown abnormalities in the past, the next person in charge can manage with the same perspective. This not only increases power generation but also enables earlier response to problems.

Having records makes it easier to evaluate the effectiveness of improvements. You can check how power generation changed before and after cleaning, whether the drop in output in the morning and evening improved after weeding, and whether the number of shutdowns decreased after equipment inspections. Even if improvement measures are implemented, without records you cannot determine whether they were effective. To continuously improve how power generation is increased, it is essential to operate on-site work and record-keeping as an integrated system.

Measure 8: Prioritize Improvement Measures and Implement Them in a Manageable Way

There are many measures to increase power generation, but you do not need to implement them all at once. In fact, if you carry out cleaning, equipment inspections, angle adjustments, and site maintenance simultaneously without identifying the causes, you will not know which measure was effective. In practice, it is important to prioritize actions that have a large impact on power generation, are easy to implement, and can be carried out safely.

The easiest first steps are checking the data and performing a visual inspection. Determine whether the drop in power output affects the entire installation, only certain strings, or specific time periods. Then look at items that can be checked from appearance, such as dirty panels, shading, weeds, and equipment displays. Even this alone can reveal the direction for improvement. For example, if output is low only in the morning, suspect shading on the east side; if the decline is most noticeable only in summer, suspect weeds or equipment temperature; if it drops during periods with little rain, suspect soiling.

Next, verify the effectiveness of each measure implemented. If cleaning was performed, compare days with similar weather before and after the cleaning. If weed removal was performed, check the power generation during the periods when shading occurred. If equipment inspection was performed, check the shutdown history and system-specific output. By checking the effects one by one, it will be easier to determine which measure should be prioritized next.

Measures that involve costs and construction will be considered carefully. Changes to the mounting angle, equipment replacement, large-scale weed control, rewiring, and similar actions need to be evaluated not only for their effect on improving power generation but also for safety, maintainability, contract terms, and long-term operating costs. If the desire to increase power generation takes precedence and you carry out poorly justified work, not only may the expected effects not be achieved, but other problems may also arise.

When determining priorities, it's easier to organize them by using the following criteria: "things that can be checked immediately," "things that can be carried out safely," "things that have a large impact on power generation," and "things that contribute to preventing recurrence." Improving power generation relies less on one-off tasks and more on creating a system to quickly identify factors causing decline and manage them continuously. By combining on-site inspections, data analysis, inspection records, and consultation with specialist contractors, improvements can be carried out without undue strain.

Summary: Increasing power generation requires combining on-site inspections and data management

To increase the power output of solar power generation, the basic approach is not to search for a single special method but to carefully eliminate the factors that cause output to decline. There are multiple elements that affect output, such as panel soiling, shading, angle, weeds, surrounding obstructions, equipment anomalies, and insufficient recordkeeping. Rather than focusing on just one issue, checking both the site conditions and the data makes it easier to make decisions that lead to improvements.

Cleaning is an obvious measure, but it is important to confirm whether dirt is truly the cause of reduced power output. Shadows change with the time of day and season, so a single visual inspection can miss them. Angle and orientation affect power output, but for existing installations an assessment that includes structural and safety considerations is necessary. Weeds and obstructions not only block sunlight but also affect accessibility for inspection and equipment maintenance.

Also, by comparing generation data daily, monthly, and by system, you can spot trends of declining power output more quickly. Abnormalities in the power conditioner or wiring affect not only power output but also safety, so early detection and professional intervention are essential. Keeping records of inspections and maintenance helps verify the effectiveness of improvements and aids handover between responsible personnel.

When trying to increase power output, the important thing is not to choose countermeasures based solely on intuition. First check changes in power output, then identify on-site factors causing the decline, and verify the effect with post-measurement data. By establishing this process, you can reduce unnecessary work while making it easier to maintain the equipment’s inherent power generation performance.

If you want to advance improvements in the energy yield of solar power installations in a more practical way, it is important to integrate on-site condition assessment with generation data management. Continuously checking cleaning, tilt angle, shading, weeds, and equipment condition—and visualizing priorities for improvement—will increase the accuracy of routine management. Rather than relying too much on specific products or temporary measures, combining on-site inspections, inspection records, and professional maintenance responses is the basic approach to detect declines in generation early and turn them into improvements.