Is low power generation normal? 5 weather-based benchmarks explained

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Are days with low power generation really abnormal?

When using solar power generation, there are days when you feel, "Today's power output is low—could it be a malfunction?", "I feel like it's generating less than last year," or "I'm worried because the monitor's readings are low."

In short, the fact that there are days with low power output is often normal. Since solar power generation relies on sunlight, the amount of electricity generated can vary greatly depending on the weather, season, time of day, temperature, shading, dirt on the panels, and so on.

Especially on cloudy or rainy days, power generation drops significantly compared with sunny days. A low power output is not necessarily a sign that the panels or the power conditioner are faulty.

Please provide the Japanese text you would like translated into English.

• Power output is extremely low despite clear skies

• Clearly not generating electricity compared to other similar nearby homes.

• It has continued to be significantly lower compared with the same month last year.

• An error is being displayed on the power conditioner.

• Power generation drops abnormally only during specific time periods.

• Even on sunny days, power generation is almost zero.

In other words, the important thing is not to assume "low power output = a malfunction", but to check whether the low output is reasonable given the weather and conditions.

In this article, to help people searching for "low power generation" ease their concerns, we explain benchmarks for five weather scenarios and clearly introduce checkpoints to distinguish whether the output is normal or abnormal.

Basics of Power Generation You Should Know

To determine whether the power output is low, you first need to understand how the output of solar power generation is determined.

The electricity output of solar power generation mainly varies with the following factors.

• Capacity of solar panels

• Solar radiation

• Weather

• Seasons

• Time zone

• Panel orientation and angle

• Air temperature

• Presence or absence of shadows

• Deterioration of panels and equipment

• Power conditioner conversion efficiency

For example, even with the same 4 kW solar power system, the daily power generation differs between a house where it’s installed on a south-facing, well-sunlit roof and a house where it’s installed on an east- or west-facing roof that is partly shaded.

Also, even when it's sunny, the sun's elevation and the hours of daylight differ between summer and winter. Furthermore, because solar panels' power generation efficiency decreases if they become too hot, "a clear midsummer day = guaranteed maximum generation" does not necessarily hold.

Do not judge power generation solely on a daily basis

If you feel the power generation is low, it is risky to judge based on the figures from just one day.

For example, if yesterday was sunny and today is cloudy, power generation can be half or less. However, this is due to the weather and is not abnormal.

When making a judgment, it is important to view it from multiple perspectives as follows.

• Is this reasonable for today's weather?

• How does it compare to other days with the same weather?

• How does it compare with the same month last year?

• Check for any extreme decreases on a weekly basis

• Whether there are no large differences on a monthly basis

Because solar power generation is affected by natural conditions, it is normal for daily power output to vary.

The criteria for feeling "low" differ from household to household

The criteria for considering power generation to be low also vary depending on the capacity of the solar panels.

For example, of course the daily power generation differs between a 3 kW system and a 6 kW system. If a 3 kW system generates 15 kWh, that's a very good day, but if a 6 kW system generates 15 kWh, depending on the conditions you might find it a bit lacking.

Therefore, when evaluating power generation, it's easier to judge if you look not only at "how many kWh were generated" but also at how much was generated per 1 kW of installed capacity.

As a guideline, on sunny days each 1 kW can generate about 3–5 kWh per day. For a 4 kW system, a useful reference is roughly 12–20 kWh on a sunny day.

However, because this can vary depending on the region, the season, and the condition of the roof, please consider it only as a reference value for verification.

5 Typical Power Generation Estimates by Weather

From this point on, we will explain how much the output of solar power generation varies with the weather, divided into five patterns.

Please note that the following estimates are intended to give an image of the daily power generation per 1 kW of installed capacity. Actual generation varies depending on the region, season, roof orientation, panel angle, and whether or not there is shading.

Pattern 1: Power generation tends to be higher on sunny days

A clear, sunny day is the most favorable condition for solar power generation. With few clouds and sunlight reaching the panels effectively, daily energy production tends to be higher.

As a guideline, about 3–5 kWh per day per 1 kW of installed capacity.

For example, a 4 kW solar power generation system can generate about 12–20 kWh on a clear day. For a 5 kW system, about 15–25 kWh is a guideline.

However, even on clear, sunny days electricity generation may not rise as much as expected. One reason for this is temperature.

Solar panels lose power-generation efficiency when ambient temperatures are too high. In particular, at midday in midsummer the panel surface can become quite hot, so even when solar irradiance is high the power generation efficiency can decrease.

Therefore, over the course of a year, there are cases where clear, sunny days in spring and autumn produce more electricity than those in midsummer.

If you feel the power output is low on a clear, sunny day, check the following points.

• Confirm that the power conditioner is not displaying any errors

• Whether any shadows are falling on the panel

• Hasn't it dropped significantly compared to the previous clear day?

• Whether the monitor's display is normal

• Has the circuit breaker tripped?

If power output is extremely low despite clear skies, there may be causes other than the weather.

Pattern 2: Slightly lower on partly cloudy days than on sunny days

On a lightly overcast day, the sun is slightly obscured by clouds. It’s not as clear as a sunny day, but because sunlight reaches through the clouds, a certain amount of power generation can be expected.

As a guideline, approximately 2–4 kWh per day per 1 kW of installed capacity.

A 4 kW system can generate about 8–16 kWh. Even if the weather forecast shows "cloudy", if it is actually bright with thin cloud cover, it can generate more electricity than you might expect.

On partly cloudy days, the amount of power generated varies greatly depending on the thickness of the clouds.

If it's bright and thinly overcast, the power output can be close to that on a clear day. On the other hand, if clouds thicken or the weather deteriorates in the afternoon, power output falls sharply.

Even if you feel that power generation is low on a partly cloudy day, it can be considered within the normal range if the following conditions apply.

• The entire sky is whitish and the sun is hazy.

• It was sunny only in the morning and became cloudy in the afternoon.

• Clouds are passing by, causing the power output to fluctuate.

• Power output was lower than on the previous day's clear, sunny day.

Partly cloudy days are characterized by unstable power output. When you look at the monitor, the readings may rise and fall, but if the changes are caused by moving clouds, they are not abnormal.

Pattern 3: Power generation drops significantly on cloudy days

On cloudy days, the amount of electricity generated drops significantly because sunlight is blocked by clouds.

As a guideline, about 1–2 kWh per day for each 1 kW of installed capacity.

For a 4 kW system, about 4–8 kWh is a rough guideline. Compared with a clear sunny day, generation can be less than half, which is not uncommon.

Even if you feel, "I generated 15 kWh (51,182 BTU) yesterday but only 5 kWh (17,061 BTU) today," if yesterday was sunny and today is cloudy, it can be considered a natural change.

On cloudy days, the power output is lower because less solar radiation reaches the panels. Solar power can generate electricity not only from direct sunlight but also from diffuse light scattered through clouds, but compared with days with direct sunlight, the power output drops significantly.

The points to check on cloudy days are as follows.

• Is the sky a light overcast or a dark overcast?

• Were the clouds thick all day?

• Was it overcast before it rained?

• Was it cloudy for a long time during the morning and evening hours?

• Whether there are any major inconsistencies between the weather and power generation on the days before and after

Cloudy days are a typical weather condition when people tend to feel that power generation is low. Even if power output is low, you don't need to worry excessively as long as the figures are consistent with the weather.

Pattern 4: Power generation is considerably lower on rainy days

On rainy days, thick clouds make it difficult for sunlight to reach the surface, so power generation is significantly reduced.

As a guideline, about 0.5–1.5 kWh per day per 1 kW of installed capacity.

With a 4 kW system, it can be around 2-6 kWh. Depending on the intensity of the rain and the brightness of the sky, there may be days when it is even lower.

Especially on days when rain continues from morning through evening, the amount of power generated hardly increases. You might look at the monitor and worry, thinking, "Is it really this little?", but low power generation on rainy days is normal.

However, rainy days do not mean that electricity generation stops completely. If the sky is bright, it will generate electricity from even a small amount of light. Conversely, on rainy days when thick, dark clouds make it dim even during daytime, the amount of electricity generated will be considerably reduced.

When looking at power generation on rainy days, it becomes easier to judge if you consider the following.

• On a drizzly but bright day: it still generates a little electricity

• A day of steady drizzle all day: it becomes considerably lower.

• On days when the sky is dark due to heavy rain: it becomes very low

• A day when the rain stops in the afternoon: slight improvement in the latter half

• Days that are sunny only in the morning and rainy from noon: power generation will be concentrated in the morning.

If the only issue is lower power generation on rainy days, that is basically not abnormal. In fact, rain can even wash away light dirt from the surface of the panels.

However, if power generation does not recover even after the weather clears following rain, you should check for other causes.

Pattern 5: Power generation may be extremely low around snow, yellow dust, and typhoons

In special weather conditions such as snow, yellow dust, and before or after a typhoon, power generation can be extremely low.

As a guideline, it may drop to about 0–1 kWh per day per 1 kW of installed capacity.

Especially when snow accumulates on the panels, sunlight cannot reach the panel surface, so power generation can be reduced to almost zero. Even if it is sunny, panels covered with snow cannot generate electricity.

Be cautious during periods when yellow sand or pollen are abundant. If fine dirt adheres to the panel surface, it can become harder for light to reach the panels and power generation may decrease. Usually rain will wash away some of the dirt, but residue may remain.

Before and after a typhoon, thick clouds and heavy rain can reduce power output, and there may also be panel scratches from flying debris, abnormalities in the mounting racks, and wiring troubles.

After unusual weather, make sure to check the following points.

• Whether there is any snow remaining on the panels

• Whether the surface is free from yellow sand or pollen

• Check whether any wind-blown debris remains on the roof after the typhoon

• Whether there are any errors on the power conditioner

• Is the power output not returning even after several days?

If snow accumulates, it is dangerous to climb onto the roof and remove it yourself. Because there is a risk of falling or damaging the panels, you should generally wait for the snow to melt naturally or consult a professional contractor if necessary.

Seasons and Times of Day When Power Generation Tends to Be Low

Low power generation is not caused solely by the weather. Power generation also varies greatly depending on the season and the time of day.

In winter, daylight hours are shorter and power generation tends to be lower.

In winter, the sun's position is lower and the hours of sunlight are shorter. Therefore, even when it's sunny, daily power generation may be lower compared with summer and spring.

It's also a season when shadows from surrounding buildings and trees tend to lengthen. Places that weren't shaded in summer can become shaded in the morning or evening in winter.

If you feel the power output is low in winter, please check the following points.

• Whether there are no shadows in the morning and evening

• Is solar power generation dropping during times when the sun is low?

• Whether there is any impact from snow or frost

• Whether there are no significant differences compared to last winter

Even if winter power generation is lower than in summer, that alone does not indicate an abnormality.

In summer, high temperatures can sometimes reduce power generation efficiency.

In summer, people tend to associate longer hours of sunlight with higher power generation. However, during midsummer panels are more likely to become hot, which can reduce their generation efficiency.

Therefore, on hot days, power output may not increase as much as expected, even when the sky is clear.

If you feel that the power output is low despite strong sunlight, reduced efficiency due to temperature may be a factor.

If power output in particular falters in the early afternoon, it may be affected by panel temperature.

It's natural for power generation to be low in the morning and evening

Solar power generation increases around midday when the sun is higher in the sky. In the morning and evening, the sun's angle is low and less light reaches the panels, so power output is lower.

When you look at a graph of a day's power generation, sunny days typically form a mountain-shaped curve.

• Morning: power generation is low

• Around midday: power generation is likely to be the highest

• Evening: Power generation gradually decreases

• Night: does not generate electricity

Don't conclude that "power generation is low" based only on morning or evening readings; check the day's total and the peak around midday as well.

Main causes of reduced power generation other than weather

If power generation is low even though the weather is fine, other causes may be responsible. Here are some common causes.

Cause 1: A shadow is cast on the panel

In solar power generation, shadows have a very large impact.

Even partial shading of the roof can reduce power output. In particular, the following are common causes of shading:

• Nearby buildings

• Utility pole

• Antenna

• Trees

• Roof level difference

• chimney

• Signboard

• Storage sheds and add-on equipment

Even if there was no shading when first installed, as surrounding trees grow or nearby buildings are constructed, shading can occur later.

If power generation falls abnormally only during specific times of the day, it may be caused by shading.

Cause 2: The panel is dirty

Solar panels are installed outdoors, so dirt accumulates on them.

Common types of dirt include the following:

• sand dust

• Yellow sand

• Pollen

• bird droppings

• Fallen leaves

• Soiling caused by exhaust gases

• Traces of raindrops

Light dirt is often washed away by rain, but bird droppings and stubborn, stuck-on grime can remain. If dirt blocks the light, power output decreases.

However, climbing onto your roof to clean it yourself is dangerous. There is a risk of accidents from working at heights and of damaging the surface of the panels. If you are concerned about dirt, it is safer to consult a professional.

Cause 3: Power conditioner malfunction

The electricity generated by solar panels cannot be used in the home as is. It is converted by a power conditioner into electricity that can be used in the home.

Therefore, if the power conditioner malfunctions, the reported power generation may appear low or power generation may stop.

Be cautious if you observe any of the following conditions.

• An error code is displayed

• The operation indicator light is off.

• There is an abnormal noise

• There is a burnt smell.

• The main unit is abnormally hot.

• Has not been restored after the power outage.

• The circuit breaker has tripped.

The power conditioner is an important component of a solar power generation system. If an abnormality is suspected, check the instruction manual and, if necessary, contact the retailer or installer.

Cause 4: Output control is active

Depending on the region and contract terms, output control may be carried out at the direction of the power company.

Output control is a mechanism that temporarily curtails the output of solar power generation to maintain the balance between electricity supply and demand. When output control is applied, the amount of power generated and the amount of electricity sold may be reduced even when the weather is good.

If it appears that power generation is being curtailed despite sunny conditions, it would be a good idea to check whether it is subject to output control.

In regions where solar power generation is widely deployed, output control measures may have an impact.

Cause 5: Decline in Power Output Due to Age-Related Degradation

Solar panels can be used for many years, but their power output gradually declines over time.

If 10 or 15 years have passed since installation, the power output may be lower than at the time of installation. This is somewhat natural.

However, if the power output drops sharply, it may not be mere degradation but could be caused by equipment malfunctions, wiring faults, or similar issues.

To determine whether it is aging-related degradation or an anomaly, it is important to compare it with historical power generation data.

Cause 6: Display Malfunctions on Monitors and Measurement Instruments

Even if the power output looks low, it may actually be generating electricity. This can occur when a monitor or communication device is malfunctioning and not displaying the correct values.

For example, the following situations can be imagined.

• The monitor's communication has been disconnected.

• Display updates are delayed

• There is a malfunction in the measurement unit.

• Data updates in the app are slow

• Wi‑Fi connection is unstable.

• Data has not been restored correctly after the power outage.

If the generated power suddenly shows zero, first check not only the monitor but also the display on the power conditioner unit.

5 Checks to Determine Whether Something Is Normal or Abnormal

If you feel the power generation is low, before hastily contacting a service provider, check the following five things.

Checkpoint 1: Does it match the weather of that day?

The first thing you should check is the weather for that day.

It is natural for power output to be low on rainy or cloudy days. Conversely, if it is clear and sunny yet the output is extremely low, caution is warranted.

The criteria for judgment are as follows.

When power generation is low, it is important to first check whether it is a "natural decrease due to the weather."

Checkpoint 2: Compare with past data from the same season

Next, let's compare it with past power generation data.

When making comparisons, rather than simply comparing with yesterday or last week, it's recommended to compare with days from the same season, the same month, and with similar weather.

For example, comparing the power generation in January with that in July does not allow for an accurate assessment, because the hours of sunlight and the sun's elevation are different.

The items you should compare are as follows.

• Power generation for the same month last year

• Power generation on sunny days in the same month

• Power generation on cloudy days of the same month

• Average power generation over the past week

• Average power generation over the past month

If there is no significant difference compared to past data, even days with low power generation are likely within the normal range.

Checkpoint 3: Examine the Shape of the Power Generation Graph

If you can check the day's power-generation graph on a power monitor or app, pay attention to the shape of the graph.

On sunny days, power generation tends to increase gradually from the morning, peak around midday, and decrease in the evening, forming a mountain-shaped graph.

On the other hand, on cloudy days the graph may become jagged due to the movement of clouds. On rainy days, it often remains low overall.

What you should pay attention to is the following graph.

• Despite clear skies, the midday peak is extremely low.

• Drops sharply at the same time every day

• Power generation drops to zero for a certain period of time.

• It suddenly stops generating electricity partway through.

• Almost zero all day despite the good weather

In such cases, you should check for shadows, output control, equipment malfunctions, and so on.

Checkpoint 4: Check the power conditioner's display

When power generation is low, check the status of the power conditioner.

The points to look at are as follows.

• Whether the operation indicator light is on

• Is an error code being displayed?

• Is it not in autonomous driving mode?

• Whether the circuit breaker has tripped

• Whether there are any unusual noises or odors

• Is the main unit abnormally hot?

If an error code is displayed, check the instruction manual for its meaning. If you cannot determine it yourself, it is safest to contact the manufacturer or the installer.

Checkpoint 5: Compare local and regional solar radiation conditions

If possible, it is also useful to compare it with the power generation situation in the same region.

If neighboring homes have also installed solar panels, the weather's effects are similar. If only your home has an extremely low power output, possible causes include shading, dirt, or equipment malfunction.

However, even within the same region, the amount of power generated will vary if the following conditions differ.

• Panel capacity

• Roof orientation

• Roof angle

• Presence or absence of shadows

• Years since installation

• Panel manufacturer

• Types of power conditioners

Therefore, use comparisons with nearby properties only as a reference.

Measures You Can Take Yourself When Power Generation Is Low

If you think your system's power output is low, there are things you can safely check yourself. There is no need to climb onto the roof.

Measure 1: Record data from power generation monitors

First, let's record the power generation data.

We recommend noting the following items.

• Date

• Weather

• Maximum temperature

• Daily power generation

• Amount of electricity sold

• Amount of self-consumption

• Characteristics of the power generation graph

• Presence or absence of error display

If you keep the data, it will be easier to determine later whether something is abnormal. When consulting a professional, having specific numerical values makes it easier to explain the situation.

Measure 2: Compare power generation by weather conditions

It's important to compare power generation under the same conditions.

Keeping separate records of sunny, partly cloudy, cloudy, and rainy days will reveal trends in your home's solar power generation.

For example, suppose a 4 kW system exhibits the following trend.

If you know this kind of home-specific benchmark, it becomes easier to determine that a day with low power generation is within the normal range—for example, "it's raining today."

Countermeasure 3: Check the cause of shadows

You can sometimes check the shadow conditions from the ground without climbing onto the roof.

On a sunny day, check the visible area of the roof about three times: in the morning, at midday, and in the evening. If shadows fall during a particular time period, power generation during that time may be reduced.

In particular, because shadows become longer in winter, shadows that were not a problem in summer can have an impact during winter.

The points to check are as follows.

• Shadows of utility poles and power lines

• Shadow of the neighboring house

• Shadows of trees

• Antenna shadow

• Shadows cast by level differences on balconies and roofs

If tree branches have grown and are casting shade, pruning can sometimes improve the situation.

Measure 4: Check the power conditioner

A power conditioner is a device that is often installed on indoor or outdoor walls. When power generation is low, check the display and indicator lights.

However, disassembling or touching the wiring is dangerous. Please limit inspections to checking the display and indicator lamps.

If an error message appears, follow the steps below.

• Note the error code

• Confirm the contents in the instruction manual

• If recovery procedures are available, try them within safe limits

• Contact the contractor if it does not improve

If the same error occurs repeatedly, a malfunction of the equipment is suspected.

Measure 5: Check announcements from your electric utility and retailers

If you find that power generation or electricity sales are low, output control, maintenance, or communication failures may be involved.

The following information can be confirmed:

• Notice from the Power Company

• Notice from the retailer

• App notifications for a solar power generation system

• Manufacturer's maintenance information

• Notification regarding output control

Especially when checking power generation in the app, there are cases where the data is simply not reflected due to communication failures.

Cases when you should consult a professional

If there are only days with low power generation, you don't need to contact the installer immediately. However, in the following cases, it's better to consult sooner.

Even on clear, sunny days, power generation is extremely low

If power generation is clearly low despite clear skies and favorable solar irradiance conditions, caution is required.

In particular, if power generation has fallen to less than half compared with previous sunny days, or is generating almost no power, there may be an equipment malfunction.

An error code is displayed

If an error code is displayed on the power conditioner or monitor, there may be some kind of fault.

Depending on the error, it may be temporary, but if left unaddressed it can lead to continued power generation losses.

Power generation has been declining for several weeks

If the power output is low for only one day, it may be due to the weather. However, if low power output persists for several weeks, including on sunny days, consider having an inspection.

In particular, if it has dropped significantly compared with the same month last year, you need to check the panels, power conditioners, wiring, and measurement equipment.

Power output has been low after typhoons and earthquakes.

If power generation decreases after a typhoon, strong winds, an earthquake, or heavy snowfall, the equipment may have been affected.

Because it's difficult to inspect the roof yourself, don't try to climb up; have a professional contractor inspect it.

Only the amount of electricity sold has suddenly decreased

If only the amount of electricity sold has decreased, rather than the amount generated, it may indicate that household electricity consumption has increased.

For example, if self-consumption increases due to air conditioners, water heaters, storage batteries, or electric vehicle charging, the amount of electricity sold will decrease.

However, if both the amount of power generated and the amount of power sold are falling at the same time, a problem on the generation side should also be considered.

How to Avoid Losing Out When Power Generation Is Low

If you feel that your power generation is low, it's natural to worry that you might be losing out. However, solar power systems do not generate the same amount of electricity every day.

The important thing is not to get excited or upset over daily power generation, but to look at monthly or annual generation.

Think in months rather than days, and in years rather than months

Power generation is lower on rainy or cloudy days, but if it generates well on sunny days, monthly and annual totals can come close to expectations.

For example, power generation tends to be lower during the rainy season, but higher generation in spring and autumn can sometimes balance out the annual total.

The recommended viewing order is as follows.

• Is it appropriate given the weather that day?

• Isn't the weekly average extremely low?

• How the monthly power generation compares with the same month last year

• Is the annual power generation dropping significantly?

Looking at them in this order makes it easier to determine whether the fluctuations are normal or abnormal.

When self-consumption increases, the amount of electricity sold decreases

Even when you feel your power generation is low, you may actually be looking at the amount of electricity sold rather than the amount generated.

Electricity generated by solar power is used in the home first. Any surplus is sold. Therefore, if household electricity consumption increases, the amount sold decreases.

For example, in the following cases, the amount of electricity sold tends to decrease.

• Time spent at home has increased.

• The time spent using the air conditioner during the daytime has increased.

• As a measure to reduce electricity bills, I started using household appliances during the daytime.

• Installed a storage battery.

• Charging an electric vehicle during the day

• I changed the operating hours of the EcoCute.

In this case, even if the amount of electricity sold decreases, since you are simply using the electricity you generated at home, it is not necessarily a loss.

Check generated power and electricity sold separately

To ease concerns, it's important to look at power generation and electricity sales separately.

• Power generation: the amount of electricity produced by solar power generation

• Self-consumption: the amount of electricity used within the household

• Electricity sold: The amount of surplus electricity that was sold to the power company

If you conclude that power generation is low based solely on the amount of electricity sold, you may misidentify the cause.

Especially recently, with rising electricity costs, more households are placing importance on self-consumption. Even if the amount of electricity sold decreases, if the amount of electricity purchased is reduced, the household budget as a whole may still benefit.

Frequently Asked Questions

Does a day with low power generation indicate a malfunction?

A day with low power generation alone does not necessarily indicate a fault. Power generation varies due to factors such as clouds, rain, snow, yellow dust, season, and time of day.

However, if extremely low readings persist even on clear days, or if an error message is displayed, consider having it inspected.

How much power is generated on rainy days?

On rainy days, power generation is much lower than on sunny days. As a guideline, it can be about 0.5–1.5 kWh per day per 1 kW of installed capacity.

However, it varies depending on the brightness of the sky, the intensity of the rain, and the season. On rainy days that are dark even during the daytime, it may be even lower.

Why do they generate electricity even on cloudy days?

Even on cloudy days, sunlight does not disappear completely. Light transmitted through clouds and scattered light still reach the panels, allowing them to generate electricity.

However, because the solar irradiance is lower than on a sunny day with direct sunlight, power generation will be lower.

What causes low power generation despite clear skies?

If power generation is low despite clear skies, possible causes include shading, dirty panels, power conditioner malfunctions, output control, wiring problems, and faulty measurement instrument displays.

First, let's check the power generation graph, the power conditioner display, and the comparison with past data.

Is it abnormal that power generation is lower than last year?

Lower power generation than last year does not necessarily indicate a fault. Year-to-year variations can result from irregular weather, the length of the rainy season, typhoons, yellow dust, temperature, and differences in sunshine hours.

However, if it has dropped significantly compared to the same month last year despite many sunny days, it may be worth considering an inspection.

Should Solar Panels Be Cleaned?

Light dirt is often washed away by rain, so frequent cleaning is not always necessary. However, if bird droppings, yellow sand, pollen, fallen leaves, or similar residues remain, they may affect power generation.

Climbing onto the roof and cleaning it yourself is dangerous. If you are concerned about dirt or stains, consult a professional contractor.

Is it okay to reset when the power output is low?

The method for resetting a power conditioner varies by model. Only carry out a reset if the instruction manual describes safe procedures.

If you are unsure or errors are repeatedly displayed, do not attempt to operate on your own; consult your retailer or the manufacturer.

Will the storage battery be charged even on days with low power generation?

If electricity is being generated, it may charge the storage battery. However, on cloudy or rainy days when generation is low, electricity for household use is prioritized and the storage battery may not become sufficiently charged.

Because charging behavior can vary depending on the battery's settings, it's a good idea to check the mode settings.

Summary

On days when power generation is low, this is often a natural fluctuation caused by the weather and the season. In particular, on cloudy, rainy, snowy, or yellow-dust days, power generation drops significantly compared with sunny days.

The guidelines for each type of weather are as follows.

If you notice that power generation is low, first check the following 5 items.

• Is it appropriate for that day's weather?

• How does it compare to past data for the same season?

• Are there any anomalies in the shape of the power generation graph?

• Is there an error on the power conditioner?

• Whether there are any effects from shadows or dirt

It is often normal for power output to be low on rainy or cloudy days. On the other hand, if output is extremely low even on clear, sunny days, if there are error messages, or if the decline continues for several weeks, it is reassuring to consider having an inspection.

Solar power generation does not produce the same amount every day. Do not judge by a single day's numbers; it is important to consider the weather, the season, past data, and the monthly power generation together.