5 Steps for Cleaning and Inspection to Increase Power Generation

When you want to increase the power output of a solar power generation system, the easiest first steps are cleaning and inspection. However, a low power output does not necessarily mean you should immediately clean the panels. There are multiple causes for reduced output, including dirt, shading, fallen leaves, bird droppings, snow accumulation, wiring or equipment malfunctions, temperature increases, and aging. To perform cleaning and inspections effectively, it is important to check generation data, assess on-site conditions, and determine the scope in which work can be carried out safely. In this article, aimed at practitioners searching for "how to increase power generation", we explain a five-step process for cleaning and inspection to increase power output.

Table of Contents

• Things to know before increasing power generation by cleaning and inspection

• Step 1: Determine the need for cleaning and inspection using power generation data

• Step 2: Check panel surface for dirt, fallen leaves, and bird droppings

• Step 3: Inspect for shadows, snow accumulation, and changes in the surrounding environment

• Step 4: Check for abnormalities in wiring, equipment, and connection points

• Step 5: Keep inspection records and verify improvement effects

• Dangerous decisions to avoid during cleaning and inspection

• Summary

What to know before trying to increase solar power generation through cleaning and inspections

When performing cleaning or inspections to increase solar power generation, the first thing to understand is that cleaning alone will not necessarily result in a significant improvement in output. If the cause of reduced generation is dirt on the panel surface, cleaning can be expected to improve it. However, if the cause is shading, equipment shutdowns, wiring faults, output limitations, weather, snow accumulation, or temperature-related losses, cleaning alone may not provide sufficient improvement.

Therefore, cleaning and inspection should be considered together. In addition to cleaning the panel surfaces, it is important to check during which seasons, at what times of day, and on which mounting surfaces the power generation is declining, and to investigate the causes on site. Depending on whether the drop in power generation is occurring across the entire system or only in some panels or circuits, the areas that need inspection will differ.

Because solar power systems are installed outdoors, they are affected by seasonal and local environmental conditions. In spring, pollen and dust; in autumn, fallen leaves; in winter, snow accumulation; and in summer, reduced output due to high temperatures are more likely to occur. If there are trees nearby, fallen leaves, bird droppings, and shadows from grown branches can affect power generation. If unpaved land, roads, factories, or farmland are nearby, soil dust and particulates may also more easily adhere.

Also, work on roofs or at heights carries risks. Just because you want to increase power generation, do not force yourself onto the roof, scrub the panel surface vigorously, or spray water on the equipment, as these actions can lead to accidents or equipment damage. Cleaning and inspections should be considered by separating tasks that can be safely checked from those that require professional work.

The purpose of cleaning and inspections to increase power generation is not to make things look tidy. It is to identify the causes that are reducing power generation and to confirm the changes before and after improvements with data. By combining power generation data with on-site checks, the areas that need cleaning, the equipment that needs inspection, and the surrounding environments that need management become clear.

Step 1: Determine the need for cleaning and inspection using power generation data

The first step in cleaning and inspection is to look at the power generation data. When you feel the power output is low, rather than immediately suspecting that the panels are dirty, first check how the power output has declined. If you clean without looking at the data, you may not achieve sufficient improvement if the cause lies elsewhere.

First, check the monthly power generation. If generation is low only in winter, short daylight hours, winter shading, or snow accumulation may be involved. If generation in summer does not increase as much as expected, check for rising panel temperatures, high-temperature conditions of equipment, and accumulation of dirt. If declines are noticeable in spring or autumn, seasonal factors such as pollen, dust, fallen leaves, or bird droppings should be considered.

Next, check the power generation by time of day. If generation is low only in the morning, shadows from buildings, trees, or rooftop equipment on the east side are suspected. If generation falls early in the evening, check for shadows on the west side. If there is an abnormal drop around midday, rooftop equipment shadows, localized soiling on the panel surface, equipment or wiring issues, or output restrictions may be involved.

If data by mounting surface or by circuit are available, we will examine them in more detail. Inspection priorities change depending on whether the overall power generation is low, only specific roof surfaces are producing less, or only certain circuits are underperforming. If only a specific surface is producing less, check that surface for soiling, shading, orientation, tilt, and tendency to accumulate leaves. If only certain circuits are underperforming, the wiring, connection points, and the condition of the power conversion equipment need to be checked.

When looking at power generation data, a simple month-to-month comparison with the previous month is not sufficient. Because solar power generation varies by season, compare it with the same month in the previous year, sunny days in the same season, and the simulation values at the time of installation. It is natural for generation to be low in months with bad weather, but if output is lower than expected even on sunny days, it is likely that cleaning or inspection is needed.

The need for cleaning and inspection should be determined from data as well as from on-site appearance. If you can identify the periods and times of day when power generation declines, it becomes clear where to focus your checks. By reviewing the data, you can more easily avoid unnecessary cleaning and unnecessary equipment responses.

Step 2: Check the panel surface for dirt, fallen leaves, and bird droppings

If power generation data indicates the possibility of soiling, next check the condition of the panel surface. Because solar panels generate electricity from sunlight, when dirt, fallen leaves, bird droppings, dust, and the like adhere to the surface, power generation decreases. Soiling often accumulates gradually, making declines in output difficult to notice.

Contaminants on panel surfaces include sand and dust, pollen, yellow sand, fallen leaves, bird droppings, exhaust-related contamination, airborne particulate matter, and residues remaining after snowfall. At sites with many trees nearby, fallen leaves and birds are more likely to cause soiling. If there are unpaved areas, farmland, construction sites, or roads with heavy traffic nearby, soil dust and particulate matter are more likely to adhere. On roofs, panels located near exhaust equipment or vents may become dirty more easily.

Dirt is more likely to affect power generation when part of a panel’s surface is repeatedly covered. If bird droppings or fallen leaves remain in the same spot, that area will receive less sunlight. On low-pitched roofs or flat roofs, rain may not wash away the dirt easily. Dirt also tends to accumulate at the lower edge of panels and around the frames.

During inspections, check which surface is dirty, whether the soiling is uniform or localized, whether the dirt naturally washes away after rain, or whether it is firmly adhered. If only a particular roof surface shows reduced power output, check whether that surface is in a location prone to influence from the surrounding environment. If the decrease in power output coincides with the location of the soiling, improvement from cleaning can be expected.

When performing cleaning, safety and protection of equipment are the highest priorities. Work on roofs carries a risk of falling, and work close to equipment carries risks of electric shock and damage. Actions such as forcing oneself onto the roof, scrubbing hard with rigid tools, applying high-pressure water, or using unsuitable detergents can lead to accidents or equipment damage. In practice, confirm the range that can be inspected safely and consider specialized measures as needed.

The effectiveness of cleaning is verified using power generation data from before and after cleaning. We check whether generation has improved on days with similar weather after cleaning, and whether output during specific time periods or on particular installation surfaces has recovered. Cleaning is an effective measure to improve power generation, but it can only be evaluated as a practical improvement measure after its effect has been confirmed.

Step 3: Inspect changes in shading, snow cover, and the surrounding environment

The third step is to inspect changes in shading, snow cover, and the surrounding environment. Even if the panel surfaces are clean, power generation can decrease if they are shaded, covered by snow or fallen leaves, or if the surrounding environment has changed. If cleaning alone does not restore power output, you need to check for changes in the surrounding conditions.

Sources of shadows include surrounding buildings, rooftop equipment, tower structures, handrails, piping, air conditioning equipment, trees, utility poles, signs, slopes, and terrain elevation differences. Shadows change with the season and time of day. Even if there is no problem in summer, shadows lengthen in winter because the sun’s altitude is lower. In the morning and evening, shadows caused by east-west obstacles are more likely to occur.

During inspections, we check the site at the times when power generation data shows a drop. If generation is low only in the morning, we focus on the east side; if generation falls early in the evening, we focus on the west side; if there is a drop around midday, we pay particular attention to rooftop equipment and penthouses near the panels. If generation is low in winter, it is important to assume winter shading and inspect accordingly.

In snowy regions, check whether snow remains on the panels and whether fallen snow is casting shadows on the front or underside of the panels. Not only the time during snowfall, but also the duration that snow remains after a snowfall affects power generation. Panels with a shallow tilt may be more likely to retain snow. It is also important to ensure that access routes for snow removal and inspection are secured.

Pay attention to changes in the surrounding environment. Changes such as trees that were small at the time of installation having grown and casting shadows, a new structure being built on neighboring land, rooftop equipment being added, or nearby construction increasing dust can affect power generation. Because solar power systems are operated over long periods, inspections need to be carried out on the assumption that site conditions will change over time.

When inspecting shadows and the surrounding environment, it's effective to record location information, photos, and power generation data together. If you document which obstacles are located where, at what times shadows appear, and how they affect power generation, it will be easier to explain during the next inspection or when consulting with a contractor.

If cleaning does not improve power generation, shadows, snow accumulation, or changes in the surrounding environment are often the cause. To increase power output, it is necessary to check not only the panel surface but also surrounding conditions that block sunlight.

Step 4: Check for abnormalities in wiring, equipment, and connection points

The fourth step is to check for abnormalities in the wiring, equipment, and connection points. If the panel surfaces are clean and shadows or snow are not significantly affecting them, yet power output is low, there may be losses or faults in the electrical path. Because the power generated by solar panels is used within the facility after passing through wiring and power conversion equipment, parts other than the panels should also be inspected.

The first thing to confirm is whether the power generation is low overall or only low in certain parts. If the generation of the entire facility is low, check the weather, solar irradiance conditions, common equipment, and any output limitations. If only some systems have low generation, check the wiring, connection points, power conversion equipment, and the condition of the panel arrays for those systems. Having data broken down by installation surface and by system makes it easier to isolate anomalies.

Wiring losses vary depending on wiring distance and the condition of connections. If wiring is long, the wiring route is complex, or connection points are difficult to inspect, it becomes harder to detect losses and faults. When installing new systems or expanding existing ones, it is important to rationally plan wiring routes and equipment locations. For existing facilities, include wiring and connection points in inspections when power output decreases.

The condition of power conversion equipment also directly affects power generation. If equipment is stopped or not operating properly, the amount of electricity available will be reduced even if the panels are generating. If generation suddenly drops, if output plateaus during certain time periods, or if only some systems are low, inspection of the equipment and connections is necessary.

Also check the equipment’s installation environment. Locations that tend to become hot, have poor ventilation, are exposed to rain or snow, or are difficult to inspect increase long‑term operational risks. It is also important to confirm whether there is sufficient inspection space around the equipment and whether it can be accessed in case of abnormalities. To increase power generation, placement and operation that allow the equipment to be kept in good condition are necessary.

Inspections of wiring and equipment may require specialized knowledge and safety measures. Operational staff should take on the role of identifying potential anomalies from power generation data and organizing the necessary scope of inspections. Hazardous work and electrical checks must be conducted under appropriate arrangements.

If cleaning and inspecting the surrounding area do not restore the power output, consider that the cause may lie in the wiring, equipment, or connections. To increase power generation, it is important to check not only the panel surfaces but also the route the generated electricity takes to reach the facility.

Step 5: Keep inspection records and verify the effectiveness of improvements

The fifth step is to keep inspection records and verify the effectiveness of improvements. Cleaning and inspections alone are not sufficient; it is important to check how much the power output improved after measures and use that information to inform future decisions. Without records, it becomes difficult to pinpoint the cause if the same problem recurs.

In the inspection record, note the date and time of the check, the weather, the status of power output, the locations of soiling, the sources of shading, the presence or absence of fallen leaves or snow, the inspection results for equipment and wiring, and any cleaning or corrective actions performed. Including photos and location information in the record makes it easier to verify the same spots at the next inspection. On sites with large roofs or expanses of land, it is important to clearly indicate which surface or which area was inspected.

In verifying the effectiveness of improvements, we compare power generation before and after cleaning or inspection. However, a simple comparison is not possible if the weather or season differs. We compare with similar sunny days, the same month of the previous year, simulated values, and time-of-day generation. We check whether generation has improved after cleaning, whether generation in specific time periods has increased after shading countermeasures, and whether system-wise generation has recovered after equipment inspections.

By maintaining inspection records, you can identify site-specific trends. If patterns emerge—such as leaves accumulating in the same season every year, certain surfaces becoming dirtier more easily, shadows appearing at the same time of day in winter, or abnormalities occurring frequently around particular pieces of equipment—it becomes easier to plan subsequent inspection schedules.

Inspection records are also useful for internal briefings and consultations with service providers. When explaining the cause of low power output, having power generation data, photos, the inspection date and time, and location information together makes sharing the cause smoother than subjectively saying "it seems dirty." It also makes it easier to determine the priority of corrective measures.

Cleaning and inspections to increase power generation are not a one-time effort. By recording them, comparing the results, and using those findings to inform follow-up measures, you can continuously improve power generation. Inspection records should be regarded as management assets for protecting power generation.

Dangerous decisions to avoid during cleaning and inspection

When carrying out cleaning and inspections to increase power output, there are decisions you should avoid. First, do not perform cleaning alone without confirming the cause just because the power output is low. Cleaning is effective if dirt is the cause, but if the cause is shading, snow cover, equipment shutdown, wiring faults, or temperature losses, cleaning alone will not improve the situation. You should examine the generation data and perform an on-site check, then select measures that match the cause.

Next, avoid attempting unsafe work on roofs. Solar panels are often installed on roofs or at heights, which carries the risk of falls and equipment damage. Working on wet roofs, sloped roofs, or in areas with poor footing is extremely dangerous. It is important not to try to handle work in locations where safety cannot be confirmed in-house.

You should also avoid cleaning methods that can damage the panels. Actions such as scrubbing hard with stiff tools, using unsuitable detergents, spraying water at high pressure, or carelessly applying water around wiring and equipment can lead to deterioration or malfunction of the system. Cleaning is intended to increase power generation, and it is counterproductive if it damages the equipment.

Also, you should be careful not to judge improvements in power generation based only on the annual total. Even if annual generation appears to increase after cleaning, it may be due to weather or seasonal effects. When evaluating the improvement effect, compare under similar conditions: sunny days with comparable conditions, the same month of the previous year, generation by time of day, and generation by installation surface. Unless you confirm the reasons for the increased generation, you cannot correctly assess the effects of cleaning or inspection.

Moreover, choosing not to record inspection results should also be avoided. If inspections are carried out but no records are kept, you won’t be able to compare when the same problem occurs next time. By recording which locations were checked, which dirt was removed, where shadows appeared, and how power output changed, continuous improvement is enabled.

Cleaning and inspections are basic measures to increase power generation, but they should not be carried out while ignoring safety, equipment protection, and data verification. By proceeding in the correct order, you can reduce unnecessary work and accident risks, making it easier to achieve improvements in power generation.

Summary

Cleaning and inspections aimed at increasing power generation should be carried out as a single, continuous process starting with checking generation data, then inspecting on-site conditions, performing necessary cleaning, verifying equipment, and validating the effectiveness of improvements. It is not enough to simply remove dirt; the basic principle of improving power output is to correctly identify the causes of reduced generation and choose countermeasures that match those causes.

Step 1 uses monthly and hourly power generation data to determine the need for cleaning and inspection. Verify which months, which times of day, and which mounting surfaces show low generation. Step 2 checks the panel surfaces for dirt, fallen leaves, and bird droppings. If soiling is the cause of reduced generation, cleaning is likely to improve output. Step 3 inspects shading, snow accumulation, and changes in the surrounding environment. Shadows, snow, tree growth, and the addition of rooftop equipment can have a major impact on power generation.

In Step 4, inspect wiring, equipment, and connection points for abnormalities. Even if the panels are generating power, problems with wiring or equipment can reduce the amount of electricity available for use in the facility. In Step 5, keep inspection records to verify the effectiveness of improvements. Check how much power generation changed before and after cleaning and inspection, and use that information to inform future maintenance plans.

What should be avoided during cleaning and inspection are performing cleaning only without confirming the cause, undertaking unsafe work on roofs, cleaning in ways that damage panels, and failing to verify improvement effects with data. Cleaning and inspection should be carried out with safety and equipment protection as prerequisites, combining data and on-site verification.

And to improve the accuracy of cleaning and inspections, it is essential to record on-site information accurately. If you can identify the installation area, rooftop equipment, obstacles, trees, site boundaries, orientation, slope, inspection routes, and potential connection points, it will be easier to sort out soiling and shading, maintenance routes, and equipment locations.

When you need to accurately record on-site the installation area, obstacles, trees, rooftop equipment, site boundaries, orientation, tilt, inspection routes, and so on, and want to carry out cleaning and inspections efficiently to increase power generation, using LRTK, an iPhone-mounted GNSS high-precision positioning device, is effective. If you can acquire high-precision location information on site, it becomes easier to organize dirt-prone locations, causes of shading, areas that should be inspected, wiring routes, and maintenance routes, and it also makes it straightforward to proceed seamlessly from cleaning and inspection records to verification of power-generation improvements and post-installation performance management. To increase power generation, it is important not to rely on intuitive cleaning, but to accurately understand the site and perform cleaning and inspections tailored to the causes that are reducing power generation.