7 Ways to Interpret PVSyst's Near Shadings | Practical Guide to Avoid Problems

In practical work designing photovoltaic systems and forecasting power generation, the way shadows are handled greatly affects the reliability of the results. In particular, PVSyst’s Near Shadings is not merely a function to check whether shading exists; it is an important clue for understanding how objects near the installation obstruct incident irradiance and ultimately influence the final energy yield. However, even when looking at the Near Shadings screen and numbers, it can be difficult to know how far to consider impacts, which figures should be weighted more heavily, and what degree of shading is acceptable.

Especially for practitioners searching for information on "PVSyst 読み方" (how to read PVSyst), Near Shadings can feel difficult. Because it deals with shadows from nearby obstacles and adjacent rows rather than distant terrain, the precision of input conditions tends to directly determine the results, and the visual appearance of shading does not necessarily correspond to power loss. A shadow that appears small can have a large impact on energy production, and conversely a shadow that looks severe may not be as problematic. If you look only at the numbers without understanding this discrepancy, you are likely to make incorrect design decisions.

To read Near Shadings correctly, you must not look simply at whether a shadow is present, but consider in sequence which object is shading which surface, at what time of day, and in what way. Furthermore, you need to distinguish whether the effect is acting as a reduction in incident solar radiation on the receiving surface, or whether the loss extends to include electrical mismatch. In other words, Near Shadings should be interpreted not as a single annual loss rate but as the overlap of geometric, seasonal, temporal, and electrical conditions.

In this article, I explain, organized into seven perspectives, how to read PVSyst's Near Shadings in practical work so you won't be troubled. First, after clarifying the meaning of Near Shadings, I summarize in order which objects cast shadows where, the difference between Shading Factor and generation losses, the concepts of Beam and Diffuse, how to assess electrical impacts, how to read by month and time of day, how to check the accuracy of the 3D scene, and how to connect this to final design decisions. Rather than merely staring at numbers, I organize reading approaches that can be used directly for layout, explanations, and reviews.

Table of Contents

• What Near Shadings is looking at

• How to interpret 1｜Read by identifying which object is shading which surface

• How to interpret 2｜Do not treat Shading Factor and power generation loss as the same thing

• How to interpret 3｜Separate beam shadows and diffuse shadows

• How to interpret 4｜Include electrical effects in the interpretation

• How to interpret 5｜Read by month and time of day

• How to interpret 6｜Question the accuracy of the 3D scene

• How to interpret 7｜Use Near Shadings to inform layout revisions

• Common misinterpretations of Near Shadings

• Order of checks to avoid problems in practice

• The accuracy of site-condition assessment affects the perceived validity of Near Shadings

• Summary

What does Near Shadings show?

Near Shadings is a concept for evaluating the impact that obstacles near an installation have on the surface of photovoltaic modules. Here, "near" refers to objects at distances that directly change the irradiance conditions of the installation, such as adjacent rows of solar modules, railings, parapets, rooftop equipment, building upstands, trees, and columns. Unlike broad-area shading such as distant mountain ranges or the horizon, near shading strongly depends on the 3D positional relationship and can cast shadows on only parts of the installation.

The difficulty with these Near Shadings is that it’s not just a matter of how the shadows look. Depending on whether an obstacle shades only part of a single module, grazes the lower edge of an entire row, or broadly affects the whole installation, the implications of the result differ significantly. Even the same obstacle will affect annual energy production differently depending on whether it has a strong impact only on winter mornings or whether it influences periods around midday throughout the year.

In practice, if you view Near Shadings merely as a single annual loss rate, you can easily lose sight of the essence. What matters is not that shadows exist, but which receiving surfaces, which seasons, which times of day, and in what form the shadows occur. Near Shadings is a feature for bringing the site's geometric conditions into the simulation, and reading it is essentially reading the layout plan itself.

In other words, looking at Near Shadings means checking how neatly the equipment placement and the surrounding environment are organized before confirming the final power generation figures. Once you can read this correctly, the effects of shading become easier to treat not merely as a disadvantage but as an element that can be controlled through design.

Reading Method 1｜Determine which object is obstructing which face

When reading Near Shadings, the first thing to do is to specifically identify which objects are shading which surfaces. This is very basic, but in practice it is surprisingly often omitted. If the shading-loss numbers catch your eye first, you may be tempted to judge solely by their magnitude, but in fact you should first sort out the sources of the shadows and the surfaces affected.

For example, whether the shading is inter-row shading caused by adjacent rows, shading from rooftop upstands, or shading from equipment frames around the installation makes a completely different difference. If it is inter-row shading, the focus of interpretation will be row spacing, racking height, tilt, and azimuth. On the other hand, if it is shading from rooftop obstructions, the focus will be the height of the obstruction, the separation from the equipment, and the relationship with the sun’s azimuth during daytime. In other words, even for the same Near Shadings, the points you need to assess differ depending on the cause.

Also, which surface is being shaded is important. Whether only some rows receive shade, only the modules at the ends receive it, or it systematically comes in from the lower edge will affect how actual generation losses are distributed. A localized shadow only at the ends and a shadow that regularly affects an entire row will have different impacts on the design even if the shaded area is the same. In practice, you need to consider not only the source of the shadow but also how it spreads on the receiving side.

If you can read it this way, when you look at the Near Shadings numbers it becomes easier to know where to return on-site. If you feel the shading loss is large, first identify the obstacle causing that number and confirm which rows or which faces that obstacle affects. Simply following this order prevents shading discussions from ending up abstract and makes it easier to link them to layout considerations.

How to Read 2｜Do not treat Shading Factor and power generation loss as the same thing

When reading Near Shadings, the next important point is not to treat the Shading Factor and generation loss as the same thing. The visible shaded area does not directly correspond to the reduction rate in power generation. If you confuse these, it's easy to be misled into thinking the loss is too large or too small relative to what you see.

Shading Factor is a convenient concept for expressing, from a geometric viewpoint, how much of an area is shaded, but power generation losses are not determined by that alone. Actual losses depend on how significant the times of day when shading occurs are over the year, which seasons they are concentrated in, where the shading occurs, and whether there are electrical mismatches, which will be discussed later.

For example, in cases where a shadow falls only on the lower edge of a row during winter mornings, the shaded area may appear relatively large visually, but its contribution to annual energy production can be limited. Conversely, if partial shading occurs during times that contribute heavily to annual generation, such as late morning in spring or autumn, it can affect energy output more than the apparent shaded area would suggest. In other words, simply looking at the shadow area is insufficient; you must also read when those shadows occur.

Understanding this point will help you avoid overreacting to the percentage of shading shown on the Near Shadings results screen. In practice, rather than simply judging that a small shaded area is safe and a large one is dangerous, it is important to consider how much those shadows are cutting out the time periods that are most significant in terms of energy. Shading Factor is input information, while generation loss is the outcome that needs to be evaluated subsequently across seasons and times of day.

Approach 3｜Treat Beam shadows and Diffuse shadows separately

Understanding Near Shadings also requires considering Beam shadows and Diffuse shadows separately. A Beam shadow is a shadow cast when the sun's direct rays are blocked by an obstacle. This is relatively intuitive: if you know the sun's position and the relative positions of obstacles, it's easy to imagine at what times of day shadows are likely to fall. For many people, the Beam shadow is the first thing that comes to mind when thinking about Near Shadings.

On the other hand, Diffuse shadows are a somewhat harder-to-read element. They are a shortfall in received light that occurs when part of the scattered light coming from the whole sky is blocked from view by nearby obstructions. Even without clearly visible, distinct shadows, if the surroundings are enclosed by walls, upstands, or equipment, the visible portion of the sky is reduced and, as a result, the Diffuse component can decrease. In other words, losses as Near Shadings can exist even in situations where there are no visible shadows.

In practice, the important thing is not to be reassured by looking only at the Beam shadows. For example, on a rooftop installation facing due south, even if the direct daytime shadows do not appear very large, if nearby upstands or walls limit the sky view, gradual losses can occur in the Diffuse component. Overlooking this can lead to the mistaken conclusion that, although it appears there are no shadows, the results will not improve.

Also, Beam shadows vary greatly with season and time of day, tending to be prominent in winter mornings and evenings or at low solar elevations, whereas Diffuse shadows tend to remain as a relatively constant geometric condition. Being aware of this difference makes it easier, when reading Near Shadings results, to see whether a given loss is season-dependent or is acting as a basic condition of the layout. To understand the impact of shading, it is important to consider not only direct radiation but also the view of the sky.

Reading 4 | Read Including Electrical Effects

What is even more important when interpreting Near Shadings is to consider the electrical effects as well. Shadows do not simply darken part of the light-receiving surface. When partial shading falls on cells or modules, it can affect the current and operating point of the entire string, causing output to drop more than the apparent shaded area would suggest. In other words, Near Shadings is not only a geometric problem but also an electrical one.

If you don't pay attention to this difference in practice, you can easily become confused, feeling that the visible shading is small while the resulting loss is large. In particular, in projects where inter-row shading or partial shading occurs regularly, the position where the shading falls and the way modules are connected can amplify the impact. Conversely, shading of a similar extent may not have such a large electrical effect if it falls differently.

Therefore, when reading Near Shadings, you need to consider from an electrical perspective where the shadows fall. For example, a case where shadows systematically fall from the lower edge of a row and a case where only part of an end is irregularly shaded can have different impacts on power generation even with the same geometric shading. You must consider not only the visible shadow but also the equipment connection layout and the way the shadow falls; only then can the Near Shadings results be interpreted practically.

Beginners often trip up here by trying to explain losses based solely on the appearance of shadows. However, in practice, when losses are greater than they look, you need to consider how those effects spread electrically. Reading Near Shadings correctly also means distinguishing between shadows that are visible to the eye and shadows that result in lost electrical power.

How to Read 5｜Read by Month and Time of Day

Viewing Near Shadings only as a single annual loss rate obscures the true nature of the shading. In practice, it is important to take a monthly and time-of-day perspective. Shading does not act the same at all times; it changes significantly with the season and the time of day. Therefore, when examining Near Shadings results, you should first determine in which months and during which hours the shading is effective.

A typical case is winter mornings and evenings. Because the solar altitude is low, inter-row shadows and building shadows tend to be long. If you look only at that moment, the losses may appear large, but their weight in the total annual energy depends on the contributions of time of day and season. Conversely, if shadows occur around midday in spring or autumn, they tend to represent relatively heavy losses with respect to annual generation. When interpreting Near Shadings, the question of "when it occurs" is very important.

A monthly perspective is also useful. If performance drops significantly only in winter, you should suspect a combination of low solar altitude and nearby obstructions. If shadows occur only at specific times in the summer, consider the relationship with the orientation of equipment and buildings. Even if the annual loss is the same, the months in which it occurs will change the design priorities.

A practical way to read the data is to always return to the monthly and time-of-day breakdowns after examining the annual values. Annual values indicate the overall magnitude, while the monthly and time-of-day data indicate the causes. If you want to understand Near Shadings as a phenomenon rather than as numbers, this back-and-forth is indispensable.

How to Read 6｜Question the Accuracy of 3D Scenes

When the results of Near Shadings feel off, the first thing to suspect is the accuracy of the 3D scene. Because Near Shadings assumes the positional relationships of nearby objects are represented in 3D, if the input shapes, dimensions, heights, separations, or orientations are incorrect, the results will of course be off as well. The difficult thing about Near Shadings is that the accuracy of how the scene is constructed has a greater impact on the results than the software’s calculations themselves.

In practice, people sometimes feel reassured after entering only the approximate dimensions from the drawings as they are. However, slight differences in the parapet height, small shifts in the positions of equipment, failure to reflect level differences of the ground or roof surface, or a misalignment of the orientation reference can all significantly change how shadows fall. In particular, nearby shadows can produce different results with errors of a few meters, or in some cases even less, so verifying input accuracy is extremely important.

Also, a 3D scene isn’t something that should simply be made as detailed as possible. What matters is including every object that causes shadows with sufficient accuracy to convey their positional relationships. Rather than obsessing over unrelated fine details, it is more practical to correctly capture the height, width, position, and distance to equipment of obstacles that are likely to be the origins of shadows. To avoid trouble when interpreting Near Shadings, you need not only the ability to read the results but also the ability to judge what level of model accuracy is necessary.

If you can read it this way, when you see results with large shading losses you won't have to immediately assume it's the design's fault. By first questioning whether the scene's assumptions are correct and whether they match the actual site, you can more easily avoid unnecessary design changes. Near Shadings is also a mirror that shows how accurately site information—not the software's internal shadows—has been brought into the model.

How to Read 7 | Linking Near Shadings to a Placement Review

The ultimate purpose of reading Near Shadings is not to check the numbers, but to link them to layout revisions. When shading losses become visible, being able to judge whether the shading can be changed by design or is difficult to change, and what to move to achieve the greatest improvement, makes Near Shadings a very powerful tool in practical work.

For example, if inter-row shading is the main cause, candidates for review include row spacing, racking height, and tilt angle. If shadows from rooftop obstacles are the main cause, options include relocating equipment, adjusting orientation, and ensuring adequate separation from obstacles. If shading is localized only at the edges, it may be more reasonable to adjust the affected rows or string configuration rather than move everything. In other words, the way you interpret Near Shadings directly translates into prioritizing layout improvements.

Also, eliminating all shading losses is not necessarily the correct course of action. If you try to completely remove near shading, the equipment area may be reduced and layout efficiency may decline, and as a result annual power generation may not increase. In practice, you need to accept a certain level of shading loss and consider which arrangement is reasonable as an overall optimization. Near Shadings can serve as input for that acceptance decision.

In other words, Near Shadings is not merely a loss check but a document for interpreting design trade-offs. Thinking about what to sacrifice and what to protect in order to avoid shading is the essence of a reading that will not cause problems in practice. It is important to consider not only the numbers but also the room for improvement and the room for acceptance at the same time.

Common Misinterpretations in Near Shadings

One common misinterpretation regarding Near Shadings is judging the severity of losses solely by the visible size of the shadow. In reality, the meaning of a loss changes depending on the time of day and season when the shadow occurs and on how the effect spreads electrically. A simple view that a large-looking shadow is dangerous and a small-looking one is safe is insufficient.

The next common mistake is focusing only on Beam shadows and overlooking Diffuse shadows. In environments surrounded by walls and equipment, even if direct shadows appear minimal, poor sky view can lead to a cumulative lack of received light. Overlooking this can lead to the mistaken belief that, because there seem to be no shadows, the results will improve — when in fact they do not.

Furthermore, it is dangerous to assume the results of Near Shadings are definitive values. If the relative positions or dimensions of the 3D scene differ from the actual site, the results will also be off. Because Near Shadings can appear precise, it's easy to become overconfident in the accuracy of the inputs, but in practice you must always question the accuracy of the underlying assumptions.

Also, ending the discussion with only the annual loss rate is a common mistake. Near Shadings only becomes meaningful when read by month and by time of day. If you evaluate it solely on the annual rate without checking when the shading takes effect, you can easily misjudge the significance of the shading.

Order of Checks to Avoid Problems in Practical Work

To reliably interpret Near Shadings in practical work, it's important to have a set order of checks. First, identify the object causing the shadow. Next, determine which surface the object is casting a shadow on, and whether it is a local shadow or a shadow affecting an entire row. After that, consider whether it is affecting Beam or Diffuse, and whether there is likely to be electrical spread.

After organizing things to that extent, return to the monthly and time-of-day results and check when the impact is strongest. Finally, determine whether that shading can be changed by design or should be accepted. If you follow this sequence, you'll be less likely to be confused by looking at the numbers alone.

In practice, it's more important to keep this sequence in mind than to think while looking at the software screen. If you get into the habit of reading in the order of cause, affected surface, type of shading, electrical impacts, timeline, and room for improvement, the results of Near Shadings become much easier to handle.

The accuracy of assessing on-site conditions influences Near Shadings' perceived credibility.

To make the interpretation of Near Shadings reliable in practice, an accurate understanding of on-site conditions is indispensable. Because near shadings are determined by the positional relationship with objects located immediately adjacent to the equipment, the results are directly tied to how accurately the positions of obstacles, the distance to the equipment, their heights, azimuths, and elevation differences are captured. Near Shadings can be said to be an element in which the precision of site information directly determines the precision of the simulation.

For example, even if rooftop equipment is displaced by only several tens of centimeters (several in), the way shadows fall can change during periods of low sun angle. Parapet height, railing overhang, separation from adjacent equipment, and slight level differences on the roof are also elements that are hard to ignore in near shading. If you read Near Shadings while leaving these conditions vague, the numbers may look plausible, but they will carry less weight in practical application.

Therefore, in practical work where you want to make full use of Near Shadings, having a way to capture the on-site spatial relationships with high precision is highly valuable. If you can accurately determine where equipment is placed, where obstacles are located, and how much the orientation is offset, the assumptions for the 3D scene will be in place and you can interpret the results with confidence.

From this perspective, the iPhone-mounted GNSS high-precision positioning device LRTK naturally becomes a means to accurately grasp on-site positional relationships. By improving on-site position verification, distance measurement to obstacles, and reproducibility of equipment placement, it becomes easier to more reliably establish the preconditions for Near Shadings. In practical work where you want to reflect the effects of shadows in the design not just by desk-based consideration but while accurately capturing on-site positional relationships, measures like LRTK are effective.

Summary

To read PVSyst's Near Shadings in practical work without difficulty, it is important to first understand what Near Shadings is observing, identify which objects are shading which surfaces, avoid treating the Shading Factor and generation loss as the same thing, separate Beam and Diffuse components, consider electrical effects, check when the shading is effective by month and time of day, and finally use the findings to guide layout revisions. Simply adopting these seven perspectives will make Near Shadings results much easier to organize.

The important thing is to read shading not as a single loss rate, but as a phenomenon produced by site conditions and layout conditions. Near Shadings is not a feature for simply confirming the presence of shade; it is a function to tie the way shading occurs and its implications to design decisions. If you avoid being led by numbers alone and consider the causes, time of day, how the shading spreads, and the potential for improvement, the overall results from PVSyst become easier to interpret.

And to make that interpretation even more reliable, it is essential to grasp the on-site positional relationships with high precision. If you want to organize the placement of obstacles and equipment that cause shading more accurately, the perspective of leveraging LRTK, an iPhone-mounted GNSS high-precision positioning device, can also be effective. By combining the ability to correctly read Near Shadings with the ability to accurately capture site conditions, it becomes easier to arrive at more convincing power generation forecasts and layout decisions.