5-Minute Check to Improve Power Output｜6 Items to Check First

Table of Contents

• Five-minute check approach to improve power generation

• Check 1: Examine how the power generation data is declining

• Check 2: Narrow down the abnormal range by comparing with equipment under the same conditions

• Check 3: Separate out weather, solar irradiance conditions, and seasonal differences

• Check 4: Inspect panel surface for soiling and shading

• Check 5: Consider potential faults in connectors, cables, and conversion equipment

• Check 6: Identify causes of recurrence from drainage, terrain, and inspection records

• Prioritization of improvements to take after the five-minute check

• Summary

The Concept of a 5-Minute Check to Improve Power Output

When you want to improve the power generation of a solar power system, the first thing you should do is not immediately start cleaning or making repairs. Even if you feel that output is low, not rising as expected, or has declined compared with before, the cause may not be a single one. Dirt on the panel surfaces, bird droppings and fallen leaves, shading from weeds or trees, faults at connection points, cable damage, stoppage of conversion equipment, output curtailment, temperature rise, poor drainage, and a lack of inspection records — multiple factors can combine to reduce power generation.

For practitioners searching "how to increase power generation," it is important to interpret the phrase "increase power generation" as bringing the system closer to a state where it does not lose the electricity it should be able to generate. In solar power generation, you cannot increase the amount of solar radiation at the site. 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 sunlight is converted into electricity with as little waste as possible. In other words, improving power generation is the task of finding on-site generation losses and reducing their causes one by one.

The idea of a "five-minute check" does not mean solving everything in a short time. It is an entry point to narrow down where to look quickly and to grasp the direction of a decline in power output. If you can quickly confirm the time periods when output is falling, the range of equipment affected, and whether the variation is a natural fluctuation due to weather or a loss that can be improved on site, it becomes easier to proceed with subsequent inspections and countermeasures. Rather than aimlessly walking around a large power plant, linking generation data with on-site conditions and checking accordingly reduces unnecessary work.

A common reason efforts to improve power generation fail is deciding on countermeasures based solely on on-site appearances. Cleaning because the panels are dirty, mowing because the grass has grown, or suspecting the equipment because it looks old—such judgments are sometimes necessary. However, if the primary cause of the generation decline lies elsewhere, those actions will not lead to sufficient improvement. Even if you clean, generation is unlikely to recover if morning and evening shadows remain, and even if you remove vegetation, daytime output will not increase if the inverters continue to experience short interruptions.

To improve power generation, it is important to decide in advance which items to check first. By checking power generation data, comparisons with facilities under the same conditions, weather and seasonal differences, panel surfaces, shading, connections, equipment, drainage, and inspection records in that order, it becomes easier to isolate the cause. This article organizes six items that on-site personnel can most easily check first into a five-minute inspection flow.

Check 1: Examine how the power generation data drops off

The first thing to look at to improve power generation is how the generation data drops. If you only look at monthly or annual generation, you won’t know when generation losses are occurring. Likewise, even when overall generation is low, the causes you should suspect differ depending on whether it’s low only in the morning, the midday peak doesn’t rise, it only falls in the evening, or there are sudden dips during the daytime. In a 5-minute check, first look at the generation curve to understand how the decline appears.

If generation is low in the morning, shadows from trees on the east side, slopes, surrounding structures, or adjacent equipment may be involved. If it is low in the evening, check for shadows on the west side and the influence of surrounding terrain. If the midday peak does not extend, possible causes include dirt on the panel surfaces, temperature rise, limitations of conversion equipment, output curtailment, and equipment shutdowns. If the generation curve suddenly drops during a sunny day, it is necessary to cross-check shutdown history and alarm logs with the timestamps.

When reviewing power generation data, use the generation curve from clear days as the reference whenever possible. On cloudy or rainy days, output can fluctuate widely due to cloud movement. This makes it harder to tell whether an issue is caused by equipment malfunction or by the weather. Using the clear-day generation curve makes it easier to spot trends such as shadows that fall at the same time each day, equipment shutdowns that occur only at specific times, and output curtailment that flattens the top of the curve.

There are two patterns of power generation decline: sudden drops and gradual decreases. When output falls suddenly, equipment shutdowns, broken wires, poor connections, or the appearance of obstructions may be suspected. When output is decreasing bit by bit, accumulation of dirt, growth of weeds or trees, deterioration of site conditions due to poor drainage, or aging of equipment may be involved. The locations to inspect on site and the priority of countermeasures differ between sudden and gradual declines.

What's important in a 5-minute check is not just seeing that power output is low, but reading the pattern of the decline. If you can identify the time of day and the shape of the drop, you'll know which direction to take for on-site inspections. If it's low in the morning, check for morning shadows; if it doesn't increase at midday, check for dirt, equipment issues, or temperature; if it falls in the evening, check for shadows on the west side. Reviewing the data is the first step to making on-site work more efficient.

Check 2: Narrow down the abnormal range by comparing with equipment under the same conditions

To identify the cause of low power output, the total for the entire plant alone is insufficient. Even if there is no obvious anomaly overall, there may be sections—some rows, some strings, or areas connected to certain power conversion equipment—that produce less power. These localized generation losses may be inconspicuous in monthly totals, but if they persist over a long period they can lead to significant losses. To improve power output, it is important to narrow down the abnormal range by comparing with equipment under the same conditions.

When making comparisons, select installations that are similar in orientation, tilt, number of panels, shading conditions, and connection configuration. If you simply compare installations with different conditions, you risk mistaking normal differences for abnormalities. Even within a power plant, generation will vary if orientation or tilt differ. The purpose of the comparison is to identify locations with consistently low output among installations that should, in principle, have similar generation.

If only part of an installation is lower compared with equipment under the same conditions, localized soiling, partial shading, poor connections, cable damage, or issues on the converter/inverter side may be suspected. For example, if a particular row is lower even on clear days compared with adjacent rows, possibilities include grass growing in front of that row, concentrated soiling at the lower edge, or a fault in the wiring route. Narrowing down the anomalous range in the data before inspecting the site increases the accuracy of the verification.

When narrowing down the range of decline, it is also important to be able to accurately pinpoint the relevant location on site. At sites where equipment numbers or row numbers are hard to read, even if an anomaly is detected in the data, it can take time to locate the corresponding spot in the field. Sometimes a photo alone does not convey the location. For power generation improvement, being able to share that location accurately among stakeholders is as important as finding the anomaly.

In a 5-minute check, it already makes sense to simply determine whether the whole system is low or only a part of it. If everything is similarly low, weather or solar irradiance conditions may be a major factor. If only a part is low, you should suspect an onsite cause. Simply being able to make this judgment greatly changes where you should look next.

Check 3: Separate weather, solar radiation conditions, and seasonal variations

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

At the same time, we must avoid overlooking real abnormalities by attributing them to the weather. If the entire plant is declining in the same way in line with local weather, the influence of solar irradiance conditions is likely significant. However, if only part of the plant is performing below normal while other equipment within the same plant is operating as usual, or if there is an obvious difference compared with equipment under the same conditions, weather alone cannot explain it. In that case, it is necessary to check for on-site causes such as soiling, shading, poor connections, equipment shutdowns, and power curtailment.

To separate weather-related causes from equipment-related ones, it is effective to compare sunny days with other sunny days or days with similar weather. Cloudy or rainy days exhibit large fluctuations in power generation, making it hard to discern the characteristics of anomalies. By selecting and checking the power output curves from sunny days, you can more easily detect effects such as shadows that fall at the same time every day, string-level anomalies that are low only on specific equipment, and equipment shutdowns that cause drops only for certain periods.

Seasonal variations are also an important consideration. In winter the sun’s altitude is lower, and shadows from surrounding trees and terrain tend to extend farther. In summer, although solar radiation is stronger, panel temperatures and temperatures around equipment rise, which can make it harder for output to increase. During periods with heavy rainfall, monthly power generation tends to be lower, and after strong winds or heavy rain you should pay attention to fallen leaves, soil and sediment, adhered debris, poor drainage, and the condition around cables.

In the 5-minute check, we roughly distinguish whether the decline is a natural weather-related decrease or generation loss that can be improved on-site. If it is a natural decline, cleaning or repairs will not immediately lead to a large improvement in power generation. Conversely, if a particular area continues to show low output even on sunny days, it is highly likely that there is room for improvement at the site. To improve power generation, it is essential to separate natural variability from equipment-side problems.

Check 4: Inspect the panel surface for dirt and shadows

The easiest things to check first on site are dirt on the panel surface and shadows. Because solar panels generate electricity by receiving sunlight at the surface, dirt or deposits reduce the light reaching the cells. The types of soiling vary depending on the site environment, such as soil dust, pollen, yellow sand, bird droppings, fallen leaves, sap, dust from nearby construction, road-derived dust, and salt-containing deposits that readily adhere in coastal areas.

Of particular concern are the band-like stains that remain along the bottom edge of panels and near the frames. It is often assumed that rain will wash them away, but in reality the flow of rainwater can collect dirt at the bottom edge and leave it there. On panels with a shallow tilt, water does not drain easily 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. During on-site inspections, you need to carefully look not only at the overall coloration of the panel but also at the bottom edge, the corners, and around the frame.

Localized deposits such as bird droppings and fallen leaves cannot be overlooked. Unlike dirt that spreads thinly over the entire surface, these cover specific spots more thickly and act as partial shading that hinders power generation. If only certain installations show reduced output, focus on inspecting the panel surfaces around those installations. Rows near trees, areas around structures where birds tend to perch, rows that are often downwind, and locations near unpaved paths are prone to dirt and deposits.

We also check for shadows at the same time. Causes of shadows include weeds, trees, fences, utility poles, surrounding buildings, mounting racks, adjacent panel rows, and monitoring equipment. Because shadows move with the time of day and season, not seeing a shadow at the time of inspection does not necessarily mean there is no problem. If shadows are low in the morning, check the on-site conditions in the morning; if they are low in the evening, observe the evening shadows. Even if there is no problem at noon, large shadows can appear in the morning and evening.

When performing cleaning or weeding, prioritize locations that have the greatest impact on power generation. If the equipment with low power output coincides with areas of dirt or shading, the priority for countermeasures should be high. Conversely, even if dirt or weeds are conspicuous, if the main cause of reduced power generation is equipment shutdown or a poor connection, cleaning or weeding alone may not lead to improvement. During on-site inspections, it is important not to judge by appearance alone but to cross-check with the data.

Check 5: Suspect abnormalities in connections, cables, and conversion devices

The causes of low power output are not limited to the panel surface or shading. Even if solar panels are receiving sunlight normally, faults in connections, cables, or power conversion equipment can prevent the generated electricity from being fully extracted. Differences in generation at the string level, loose terminals, poor contacts, damage to cable sheathing, moisture ingress, animal damage, shutdowns of conversion equipment, and output curtailment are important causes of reduced power output.

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

Faults in connection points or cables are suspected when only certain equipment shows low power generation, when anomalies tend to appear after rain, when power generation suddenly drops, or when the output fluctuates unstably. In areas with heavy weeds, it becomes difficult to inspect the condition of cables. In locations with poor drainage, moisture and standing water can affect connection points. At sites that are prone to animal intrusion, cable damage may also occur.

For the conversion equipment, check the operating status, shutdown history, alarm history, and whether output curtailment is present. Even a short stoppage can cause large losses if it occurs during daytime when power generation is high. If the generation curve on sunny days flattens out, check for output curtailment, equipment capacity limits, temperature rise, measurement anomalies, and so on. Do not judge solely by the generation curve; it is important to review equipment records together with on-site conditions.

When checking electrical equipment, safety is the top priority. Even if you want to improve power generation, on-site personnel should avoid forcibly touching connection points or the inside of equipment to make a judgment. At the 5-minute check stage, organize which equipment is suspected to be abnormal, the time of occurrence and changes in power generation, and whether there are signs of abnormalities in on-site photos or the surrounding environment. It is important to arrange for a professional inspection as needed.

Check 6: Identify causes of recurrence from drainage, topography, and inspection records

To improve power output, it is necessary to check not only the panels and equipment but also the plant’s overall drainage, terrain, and inspection routes. Areas where water tends to accumulate, locations where sediment flows in, passages that easily become muddy, slope failures, scour around racking, and spots where cables are likely to be exposed can directly or indirectly cause reductions in power generation. These are important factors that lead to soiling, weed growth, connector faults, and reduced accessibility for inspection.

Areas where puddles remain after rain are more likely to see weed growth. When weeds grow, they create shade, reduce ventilation, and make inspections more difficult. Muddy walkways can delay work and reduce the frequency of cleaning and weeding. Where sediment flows in, it can accumulate beneath panels and around cables, causing dirt and damage. If the same problems recur in the same locations despite cleaning and weeding, drainage or topography issues should be suspected.

When inspecting topography and drainage, on-site checks after rain are as useful as those conducted in clear weather. Determine where water flows in, where it pools, and where it drains away. Recording puddles, sediment accumulation, vegetation overgrowth, pathway subsidence, and changes to slopes will reveal locations prone to recurrence. If poor drainage is left unaddressed, dirt and weeds will recur, resulting in repeated power generation losses.

Inspection records are also important for identifying causes of recurrence. If you can check whether the same location has shown dirt before, whether weeds have grown in the same row, or whether the same equipment has experienced stoppages, you can narrow down the cause more quickly. If records are insufficient, start keeping photos, date and time, equipment number, location, details of abnormalities, and response status from this inspection so they can be used for the next check.

The purpose of finding recurrence causes during a 5-minute check is not just to fix the anomaly on the spot. It is to identify locations where the same cause repeats so you can inspect them before power output drops significantly next time. Don’t just clean off the dirt—check why the area gets dirty. Don’t just cut the grass—look into why grass tends to grow in that spot. This perspective forms the foundation for sustaining improvements in power output.

Prioritization of improvements to be made after a 5-minute check

Once a 5-minute check reveals the general causes, the next step is to prioritize improvements. Trying to solve all problems at once increases the workload and can result in measures that would have the greatest impact on power generation being delayed. When improving power generation, it is practical to address issues in order of those that cause the largest generation losses, those whose impact lasts the longest, and those that are most likely to recur.

For example, if power generation data show that only a particular column is low and that column has concentrated soiling or bird droppings along the lower edge, cleaning should be given high priority. If power generation is low only in the morning and shadows from trees or weeds on the east side can be confirmed, prioritize shadow mitigation. If only a particular string is low and no dirt or shading is apparent, proceed to check connections, cables, and converter-side equipment. If the same location shows abnormalities after rain, review drainage, moisture, and the environment around the cables.

After improvements, check how power output has changed. After carrying out cleaning, weeding, repairs, equipment checks, and drainage inspections, record the power output before and after the work, site photos, the scope of work, and the weather conditions. It is difficult to completely eliminate the effects of weather, but by comparing sunny days with each other or by comparing installations under the same conditions, you can identify consistent trends. Prioritize measures that showed a large effect in future work, and if an effect is not apparent, suspect other causes.

Also, improvement measures cannot be completed in a single operation. A solar power plant is an outdoor facility, and its condition changes with the seasons, weather, surrounding environment, and the aging of equipment. Even if cleaned, dirt will return; even if weeds are removed, grass will grow back; trees will grow; and equipment and wiring will change condition through long-term operation. To stably improve power generation, a system for continuous inspection and countermeasures is necessary.

When multiple people are responsible for management, it is also important to be able to accurately share the same location. In a large power plant, similar rows and equipment may be lined up, so photos alone can make it difficult to identify locations. If you record equipment numbers, location information, photos, and work histories together, on-site staff, management staff, inspection staff, and repair staff can more easily confirm the same location. Recording the results of 5-minute checks and using them next time is an important workflow for continuously improving power generation.

Summary

In the 5-minute check to improve power generation, it is important to sequentially review the six items to be checked first and roughly isolate the causes of generation loss. In solar power generation, you cannot increase the amount of solar irradiance at the site itself. However, you can improve generation by bringing the system closer to a state that converts the received irradiance into electricity without waste. To do so, you need to check, in order, generation data; comparisons with equipment under the same conditions; weather and irradiance conditions; panel surface soiling and shading; connection points and conversion equipment; and drainage and inspection records.

When you feel power generation is low, rather than immediately performing cleaning or repairs, it is important to first break down and examine the data. Determine when output is low, which equipment is underperforming, and whether there are differences compared with equipment under the same conditions. By then inspecting the site, you will be able to identify locations that need cleaning, the areas requiring weed removal, connection points that need inspection, equipment that should be checked, and drainage or access routes that need to be reconsidered. A five-minute check is a quick way to get a sense of the likely cause and serves as the entry point for deciding the next steps.

Also, improving power generation is not something that can be completed in a single operation. Even if you clean, dirt will return; 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 measures, keeping on-site photos and work histories, and applying them to the next inspection, the accuracy of improvements will increase. To consistently increase power generation, 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.

Especially at large power plants, a mechanism for accurately sharing the locations of problems is important. If dirty-prone rows, areas where shadows occur, places where water accumulates, abnormal strings, repair locations, cleaning ranges, and inspection photos are recorded together with location information, stakeholders can more easily confirm the same location. By combining power generation data with on-site location information, it becomes easier to explain priorities for cleaning, weeding, and repairs, and it also streamlines verification of recurrence in subsequent inspections.

If you want to continue performing the 5-minute check to improve power generation based on field data, leveraging LRTK can also be effective. LRTK, an iPhone-mounted GNSS high-precision positioning device, is useful for recording inspection positions within a solar power plant, dirt-prone areas, places where shadows occur, poor drainage spots, abnormal equipment, repair locations, cleaning ranges, and on-site photos together with high-precision location information. By recording the verification results of the six items you should check first with location information, it becomes easier to proceed with power generation improvements based on field data rather than intuition.