5 Checks to Avoid Missing a Drop in Power Output After a Typhoon

Even if you feel that a solar power system’s output is low after a typhoon has passed, it is premature to assume it is a fault immediately. There are multiple factors that can reduce output: lingering clouds, solar irradiance, temperature, power outages or impacts on the grid side, communication failures, dirt or shading, and protective shutdowns of equipment. At the same time, after a typhoon there may also be issues such as dirt on panel surfaces, loosened mounting racks or wiring, shading from flying debris, stoppage of the power conditioner, and abnormalities around junction boxes. If these are overlooked, not only can the generation decline persist, but safety checks may also become necessary. What is important is to avoid forcing your way into dangerous locations, combine generation data with visual inspection, and narrow down possible abnormalities one by one.

Table of Contents

• Compare power generation before and after the typhoon under the same conditions.

• Check the monitor display and stop history for any abnormalities.

• Check the panel surface for dirt and shading caused by airborne debris.

• Check for changes to the mounting structure and wiring within safe limits.

• If the decline continues, keep a record and seek specialist evaluation.

• To avoid overlooking post-typhoon drops in power generation

Compare power generation before and after a typhoon under the same conditions

When you suspect a drop in power generation after a typhoon, the first thing to check is to compare the power output before and after the typhoon under conditions as similar as possible. Because solar power generation is heavily affected by the weather, simply noting that it is “less than yesterday” or “less than last week” can make it difficult to determine whether an anomaly exists. Immediately after a typhoon passes, clouds tend to linger, and even if the sky looks bright, thin clouds or humidity can weaken solar irradiance. In addition, after strong winds, temperature changes or intermittent inflows of rain clouds can make the power output waveform unstable.

The basic approach for verification is to compare a clear day before the typhoon, a clear day after the typhoon, and a day with similar weather in the same month of the previous year. In particular, if the day on which you feel “power generation is low” was cloudy or rainy, the cause may be differences in solar irradiance rather than an equipment malfunction. Conversely, if clear weather has returned after the typhoon but generation during the same time period remains clearly lower, it is worth proceeding with checks on the equipment side.

When comparing, it is important to look not only at the total daily generation but also at the generation curve by time of day. Depending on whether output is generally low from morning through afternoon, drops sharply only around midday, or only fails to rise in the morning and evening, the suspected causes differ. If output is generally low, consider insufficient solar irradiance, widespread soiling of the panel surfaces, shutdowns of multiple circuits, or output control and grid-side influences. If output is low only during specific time periods, check for shading from airborne objects or changes in the positions of surrounding objects, the leaning or collapse of trees or billboards, and the effects of partial soiling.

When comparing before and after a typhoon, looking at generation relative to installed capacity is also useful. If a single power plant has multiple power conditioners or multiple circuits, comparing by equipment unit or by circuit makes it easier to narrow down anomalies than looking only at total generation. If only a particular part is lower after the typhoon, physical changes may have occurred around that section. On the other hand, if all sections are similarly low, consider factors common across a wide area such as weather conditions, grid-side control, overall soiling, or missing remote monitoring data.

One thing to be careful of is not to draw conclusions based on just the day immediately after a typhoon. Rain can wash dirt off panel surfaces, but sand blown up by the wind, sea spray, fallen leaves, and mud splashes can remain. In coastal areas, contaminants containing salt can adhere and make it harder for power generation to recover even after clear weather returns. However, the impact of soiling depends on the extent of the coverage, the circuit configuration, and irradiance conditions, so don't assume output will necessarily drop significantly; it's easier to assess by observing the trend over several days.

In practice, when checking power output, don’t rely solely on intuition; recording the date and time, weather, generated power, monitor readings, and any observations will make subsequent follow-up easier. When investigating low generation, having records you can review later makes a difference in narrowing down the cause. Although the period after a typhoon often brings overlapping on-site work, the first step is to calmly compare the data and determine whether the decrease can be explained by normal weather variation or whether it indicates the need for equipment inspection.

Check the monitor display and shutdown history for abnormalities

Next, what you should check is the operating status displayed on the generation monitor or management screen. When power generation drops after a typhoon, you need to check not only the appearance of the panels and mounting structures, but also whether the power conditioner is operating normally and not stopped or in standby. The cause of low generation may be not equipment damage, but delayed recovery after a power outage, activation of protective functions, communication failures, or temporary shutdowns due to conditions on the grid side.

The first thing to check is the current operating status. If you can see states such as generating, standby, stopped, or error indications, check whether the display has changed after the typhoon. If the display remains “stopped” or “standby” even during sunny periods, the low power output may not be due solely to insufficient solar irradiance. However, because the names and contents of the displays vary by equipment, do not determine the cause from the display alone; it is important to verify according to the instruction manual or the guidance of maintenance personnel.

If stop histories or error logs are observed, cross-check them against the times when the typhoon approached, when power outages occurred, and when wind and rain were strong. Even if stop records remain during or immediately after the typhoon, it may not be a major problem if normal operation was restored afterward. On the other hand, conditions such as the same fault recurring, only certain power conditioners failing to resume operation, or repeated short cycling between operation and stoppage should be treated as items requiring inspection.

Communication status is another commonly overlooked item to check. If power generation appears low after a typhoon, the actual output may not have decreased; rather, a communication interruption could have caused missing data. If the values on the management dashboard are not updating, remain stuck at the same value, or only some of multiple installations are not communicating, you need to distinguish between a malfunction of the generation equipment itself and a communication-system problem. In the case of communication failure, the local display may show generation while the remote dashboard shows low output.

Also, attention should be paid to the timing of power restoration after outages. If a typhoon causes outages in surrounding areas, generation equipment may temporarily shut down during periods when the power grid is unstable. Even after power is restored, operations may not immediately return to normal; equipment may perform safety checks before resuming operation. If generation output is low only during the morning after a typhoon and then returns to normal, such temporary shutdowns may have been a factor.

However, just because an error notification has disappeared does not necessarily mean everything is fine. For example, debris may cast a shadow over some panels, yet the power conditioner may continue normal operation. Dirt on the panel surface or a drop in output from some circuits may also not appear as distinct errors. Therefore, checking the monitor is important, but you should not stop there; you need to verify it together with the power generation curve and the on-site conditions.

As a field operator, after a typhoon it's important not to assume "it's fine because there are no errors," but to check in order whether there are any display anomalies, whether a drop in power generation matches the displayed information, and whether there is a communication loss. When you notice low power generation, checking the monitor display and shutdown history first makes it easier to narrow the range to inspect on site and reduces unnecessary entry into dangerous areas.

Check the panel surface for dirt and for shadows caused by airborne debris

Typical factors to check when power generation decreases after a typhoon are dirt on the panel surface and shadows caused by airborne debris. During a typhoon, strong winds and rain can move sand, soil, fallen leaves, small branches, pieces of plastic, nearby materials, and so on, which can remain on or around the panels. Even if it appears that rain has washed them away, mud can dry and remain as a film, and in areas near the sea, dirt containing salt can adhere. Such soiling can affect power generation depending on its extent and location.

When inspecting, do not force yourself to climb onto the roof or other high places; check the overall appearance from a safe position. Even for ground-mounted installations, avoid getting too close because there may be muddy ground, fallen trees, severed wiring, or loose components. Visually check whether streaks of mud remain on the panel surfaces, whether fallen leaves have accumulated, or whether branches or airborne debris are casting shadows. Even if only part of a panel surface is covered, it can affect power output depending on the circuit configuration.

When inspecting shadows, be aware of changes by time of day. If nearby trees have been tilted, signs or fences bent, or temporary structures moved by a typhoon, shadows may fall only in the morning, only at noon, or only in the evening. If the power generation curve shows a drop only during a specific time period, checking how shadows appear during that period within a safe range makes it easier to identify the cause. Objects that did not cast shadows before the typhoon may change position or angle afterward and create shadows.

The appearance of panel soiling differs depending on whether it is thinly deposited across the entire array or concentrated in a specific area. When a thin layer of dirt spreads over the whole array, power generation tends to decrease overall. On the other hand, if leaves or branches are concentrated in one spot, it may appear as only certain circuits producing less, or as unnatural steps in the generation curve. If data from multiple power conditioners or by circuit are available, checking which range shows a drop makes it easier to correlate that decline with the location of soiling or shadows.

When cleaning, it is important not to attempt work beyond your ability or rely solely on your own judgment. Wet panels, roofs, mounting structures, and slopes can be slippery, and scaffolding and the surrounding ground may be unstable after a typhoon. Also, because photovoltaic equipment generates voltage during the daytime, tasks involving water or work at height carry hazards. Even light-looking dirt, if cleaned incorrectly, can scratch the panel surface or create a risk of electric shock or falling. If on-site work is necessary, follow the equipment's management rules and consult a professional contractor as needed.

Photographic records also help determine whether low power generation is caused by dirt or shading. If you have photos from before the typhoon, comparison is easier, and if you record the positions of debris or shadows first noticed after the typhoon, you can later check their relationship with the generation data. When taking photos, prioritize capturing the whole system, the sections suspected of reduced output, and changes in nearby objects from a safe distance rather than approaching hazardous areas. Because declines in power generation are hard to diagnose from numbers alone, making a habit of reviewing data together with on-site photos makes it easier to avoid overlooking issues after a typhoon.

Check that changes to mounting racks and wiring are within safe limits

After a typhoon, if low power generation persists, attention is needed not only to the panel surface but also to changes around the mounting structure and wiring. Strong winds exert large forces on panels and racks. Even if there is no obvious visible damage, there may be loosened fastenings, shifted structural components, pulled wiring, wet connections, or sagging cables. These issues may not immediately manifest as a complete stoppage of generation; they can present as reduced output or unstable operation.

The prerequisite for inspection is ensuring safety. Post-typhoon installations can present hazards such as severed power lines, lifted metal components, cracked panels, toppled mounting racks, and muddy ground. Because power-generating equipment can be energized during the day, you should avoid approaching damaged wiring or connections. Even when field personnel carry out inspections, the basic practice is to first look for visible changes from a distance rather than touching equipment. If abnormalities are suspected, do not touch energized parts and arrange for a professional inspection.

On the racking, inspect whether there are any unnatural steps in the alignment of the panel rows, whether the tilt has changed, whether fasteners have come loose, or whether any structural members are bent. After a typhoon, changes in the panels' orientation or angle can alter how they receive solar radiation and reduce power generation. Even slight misalignments can cause shadows from steps between adjacent panels or change how water pools and dirt remains. If a section with low power generation has been identified, prioritize checking whether the racking in that area has experienced any changes.

Around wiring, check whether cables have come loose and are sagging, whether cable ties are broken, whether they are rubbing against the ground or metal components, and whether there are puddles or mud accumulation around junction boxes. Typhoon winds can shake cables and place stress on any weakly secured sections. If flying debris snags the wiring, even a small visible change can lead to contact failures or insulation faults internally. These abnormalities can affect not only power output but also safety, so it is important not to leave them unattended.

Junction boxes, combiner boxes, and the areas around power conditioners should also be inspected. Check whether doors are open, whether the exterior has dents or damage, whether there are signs of flooding nearby, and whether vents or drainage areas are clogged with leaves or mud. If equipment has stopped after a typhoon, consider the possibility that moisture entered the interior or that protective functions have activated. However, internal inspections of equipment and recovery operations may require qualifications or management authority. Limit checks to reading displays and recording external conditions, and if you are uncertain, contact the maintenance personnel.

Also, changes in the surrounding environment should not be overlooked. Fallen trees, leaning fences, displaced materials, the influx of sediment, and puddles caused by poor drainage can lead to reduced power generation and equipment trouble. In particular, for ground-mounted solar power systems, the ground can loosen after a typhoon and the area around the mounting foundations may be scoured. If there are traces of soil having been washed away around foundations or support posts, even if power output has not yet been greatly affected, the condition may worsen during the next strong winds or heavy rain.

When power generation is low, it's easy to suspect only electrical faults, but after a typhoon physical changes can be reflected in the generation data. Checking mounting structures and wiring is important not only for restoring output but also for preventing accidents. Perform a visual inspection within a safe range, record photos and the date and time of any suspected abnormalities, and establish a process to pass them on for professional verification so that the quality of post-typhoon response remains consistent.

If the decline continues, keep records and seek specialist evaluation

If the post-typhoon drop in power generation is caused by temporary weather differences, generation will return to near-normal as sunny conditions resume. However, if generation does not recover despite continued sunny days, if only specific circuits show low output, if abnormal indicators recur, or if there are unnatural dips in the generation curve, you should arrange for a professional inspection promptly. Leaving a low-generation condition unaddressed for an extended period can affect not only the amount of power sold and self-consumption, but also delay the detection of equipment faults.

Before involving a specialist, what the on-site staff should organize are: power generation data from before and after the typhoon, weather conditions, monitor displays, shutdown history, on-site photos, and any observed changes. Having these together makes it easier for maintenance personnel to narrow down the cause. For example, saying only "overall output has been low since the day after the typhoon" is too broad, but if you have information like "on a sunny day after the typhoon, only a specific power conditioner had low output from the morning, and there are leaves and branches remaining on a nearby row of panels," the scope of what needs to be checked becomes clear.

In records, it is important to keep not only the power output figures but also the comparison benchmarks. Lining up data such as a clear day before a typhoon for the same equipment, a nearby sunny day, and, if possible, data from the same period in the previous year makes it easier to convey the extent of any decline. Because power output varies by season, directly comparing summer and winter, morning and midday, or sunny and cloudy conditions can lead to misunderstandings. If you preserve the premises of the comparison, judgments are less likely to drift when reviewed later.

On-site photos should include both overviews and close-ups. Overview photos help identify which sections may have abnormalities and how the positions of surrounding objects have changed. Close-up photos allow you to check for dirt, debris, tilting, sagging wiring, and damage to equipment enclosures. However, you should not enter hazardous areas solely to take photos. After a typhoon, prioritize safety over keeping records when inspecting equipment. If there is danger, do not approach; note that fact and share it with the appropriate specialist.

Signs that commonly require professional inspection include a condition in which power generation clearly does not return even on sunny days; a condition in which only specific equipment has stopped; repeated errors or alarms; suspected safety-related abnormalities such as burn marks or strange odors; and obvious damage to panels or mounting structures. In such cases, users should avoid repeatedly attempting to restart the system or touching the wiring, as doing so may worsen the condition or increase safety risks depending on the cause.

Also, because post-typhoon declines can affect insurance and repair decisions, documentation at the time of discovery is important. If you organize which typhoon it followed, the affected area, what changes occurred, and how much the power generation declined, confirmations among stakeholders will go more smoothly. The causes of reduced power generation are not necessarily singular; dirt, shading, equipment shutdowns, wiring abnormalities, and communication failures may overlap. Keeping records and isolating issues step by step will ultimately shorten the time to restoration.

In practice, leaving post-typhoon responses to an on-the-spot decision each time makes it easy to miss checks. Deciding on a flow—check power generation data, verify the display/readout, safely inspect the site exterior, take photographs, and, if the decline continues, connect to a specialist inspection—helps maintain response quality even when personnel change. Beginning to record as soon as you feel the power generation is low is a practical measure to prevent overlooking issues.

How to Avoid Overlooking Post-Typhoon Declines in Power Generation

A drop in power generation after a typhoon can be due solely to the weather, or it can be an early sign of an equipment anomaly. What’s important is not to panic at the low output alone, but to calmly check in this order: comparison conditions, operation display, dirt and shading, mounting structures and wiring, records, and professional verification. By doing so, you can reduce unnecessary work while making it less likely to overlook abnormalities that truly require inspection.

After a typhoon, even if the site’s appearance hasn’t changed much, power generation data may show changes. Conversely, fallen leaves or dirt at the site may have only a minor impact on power generation. That is why it is important not to separate data analysis from on-site inspections, but to assess both together. Simply determining whether a decline in power generation is temporary or persistent, and whether it is a system-wide or localized issue, can greatly change the subsequent response.

For operations staff, the ideal is not to scramble after a typhoon hits but to retain pre-typhoon data and on-site photos for comparison. If you know the pre-typhoon condition, it's easier to determine what has changed afterward. By routinely tracking trends in power generation, output differences among equipment, times prone to shading, and locations that tend to get dirty, you can detect post-typhoon declines more quickly.

To avoid overlooking the causes of low power generation, a system that enables continuous monitoring is more useful than one-off inspections. If daily generation, time-of-day output, abnormal/error indications, and on-site photos can be managed together, changes after a typhoon can be detected more quickly. When information is scattered every time you check, it takes longer to isolate causes and it becomes harder to determine the priority of responses.

To avoid missing a drop in power generation after a typhoon, it is important not to approach hazardous locations, not to make definitive judgments based on data alone, not to be reassured by appearance only, and to keep records and connect them to professional inspection. If you establish a management system that can continuously monitor the condition of the power generation equipment, it becomes easier to detect declines and share them with stakeholders. When you feel that power generation is low, it is especially important not to hastily carry out recovery operations; instead, prioritize safety and methodically isolate causes one by one.