How to configure shading effects in PVSyst | 5 foolproof steps

Table of Contents

• Why shadow settings are important in PVSyst

• Basics to understand before setting shadow effects

• How to set shadow effects in PVSyst｜5 steps to avoid mistakes

• Common mistakes in shadow settings and how to address them

• How to interpret the calculation results

• Practical steps to improve the accuracy of shadow settings

• Summary

Why Shadow Settings Are Important in PVSyst

In solar power generation simulations, attention tends to focus on azimuth and tilt angles, module ratings, and meteorological conditions, but one factor that can greatly influence expected power generation in practice is shading. On site, sunlight can be blocked by various factors such as protrusions on building roofs, nearby trees, adjacent buildings, terrain undulations, and insufficient spacing between equipment. If these shadows are not properly modeled in estimates, you may overestimate generation compared with reality, which can affect design and investment decisions.

One point that practitioners should pay particular attention to is that the effect of shading is not simply a slight reduction in solar irradiance. Depending on the time of day when shading occurs, the extent of the shaded area, and how the generation equipment is wired together, losses can manifest differently even for the same shaded area. A case where shading occurs only in the morning and evening and a case where, in winter, long shadows extend across entire rows have completely different impacts on annual energy production. Furthermore, even obstacles that appear small can cast long shadows during periods of low solar altitude, resulting in larger-than-expected losses.

The purpose of configuring shading in PVSyst is not merely to place obstacles. It is to model when, where, and to what extent shading will occur, and to translate that into forecasts of annual energy production and losses. In other words, shading configuration is closer to reproducing generation behavior than to reproducing visual appearance. Keeping this perspective in mind makes it easier to understand that the input work is not just table-filling or shape entry but an important step in validating the soundness of the design.

Shading settings are also a stage where rework tends to occur. After creating a layout, if changes are made—such as slightly widening the spacing between module rows, adjusting the height of obstructions, or changing the orientation—the resulting energy yield can change more than you might expect. Conversely, if shading settings are done properly, it becomes easier to compare the effects of design changes at an early stage and to narrow down layout proposals with a sound basis. In practice this difference is significant: the higher the accuracy of the initial study, the more you can reduce rework and the burden of explanation in later stages.

Many people searching for "how to use PVSyst" are likely worried not only about which screen to open, but also how detailed the settings should be, what mistakes can skew the results, and how to convert site information into inputs. Shading settings are exactly where these concerns are concentrated. For that reason, it is important to understand not just the operation steps, but the rationale behind the settings and an input order that prevents mistakes.

Basics to Understand Before Setting Shadow Effects

Before you start configuring shadow settings, the first thing to understand is that shadows can be broadly divided into distant obstructions and near obstructions. Distant obstructions are factors that narrow the sun’s visible range, such as mountain ranges near the horizon or groups of distant buildings. In contrast, near obstructions are factors that cast shadows on individual module surfaces, such as obstacles close to the installation plane or interference between rows of equipment. When dealing with shadow effects in PVSyst, it is important not to confuse these two. Distant obstructions limit how solar irradiation enters, while near obstructions cause partial shading on equipment surfaces. Because their roles differ, the approach to configuring them also differs.

Next, it is important to understand that assessing shadows requires both accurate geometry and an understanding of electrical grouping. For example, even if you only enter the approximate height of an obstacle, the way shadows fall will change if the positional relationships are off. Conversely, even if you model shapes in detail, you can misinterpret the results if your view of how they affect which equipment groups is unclear. Shadow configuration is both the work of reproducing three-dimensional geometry and the work of structurally grasping the causes of power generation losses.

Furthermore, balancing precision and work efficiency is important when setting up shading. In practice, it's not always best to create a fully detailed model. During the initial assessment stage, it is more efficient to first identify large obstructions and clearly dominant shadow factors, and then refine the necessary areas once the design approach is established. Reproducing every detail of piping, handrails, and support structures from the outset can increase input time while providing only limited improvements in accuracy. The important thing is to distinguish shadows that significantly affect annual energy production from those that have little effect.

A commonly overlooked point for practitioners is the discrepancy between on-site verification and design drawings. Even clearances that appear fine on drawings can differ in the field due to variations in equipment foundation heights or the positions of existing items. Especially in renovation projects and on existing roofs, there can be steps, upstands, inspection walkways, equipment platforms, and other features that drawings alone cannot fully capture. If you want to improve the accuracy of shadow settings, you must not rely solely on drawings; it is essential to combine on-site photos, measured values, and information confirming positional relationships.

Also, before you enter shadow settings, clearly defining which cases you want to compare will keep the work from drifting. Whether your goal is to compare layout proposals, to see how much improvement occurs when avoiding obstacles, or to verify the validity of the current situation will change the level of detail the model should have. If you start inputting data while the comparison objective is vague, you will likely have to realign the conditions later. Because shadow settings take time to input, it is important to decide up front what the model is intended to evaluate.

How to Configure Shadow Effects in PVSyst | 5 Foolproof Steps

When configuring shadow effects in PVSyst, the key to avoiding mistakes is to work through a single workflow—from organizing information to verification—rather than entering items in the order they occur to you. Here, the process is organized into five steps that are easy to reproduce in practice.

The first step is to organize the elements that cause shadows. Before you start creating a 3D model on the screen, identify what could cast shadows. Typical examples include surrounding buildings, trees, rooftop equipment, parapets, adjacent rows of equipment, slopes and embankments of developed land, and obstructions along the site boundary. At this stage, what’s important is not to include everything that is visible, but to prioritize those most likely to actually block incoming sunlight. Give priority to tall, nearby objects rather than low, distant ones, and to items that produce long shadows at the low solar altitude in winter. If you can determine each object’s position, height, width, and distance to the installation surface at this point, later data entry will be much easier.

Step 2 is to align the installation conditions and coordinate relationships. A 3D shadow model is meaningless unless its relative position to the equipment layout matches. Therefore, first organize the orientation, tilt, row spacing, height, and the way reference points are defined for the equipment surface, and decide which point you will treat as the origin. In practice, even if you only know the standalone height of an obstacle, the relative height as seen from the installation surface can be ambiguous. For example, input values will differ depending on whether the reference is height from ground level, an upstand from the roof surface, or the top edge of the mounting structure. If this reference shifts, an obstacle’s shadow may exist but fall in a different location on the model. In PVSyst, what most often causes errors in shadow settings is not mistyped numbers but misidentification of the reference surface. Therefore, matching the reference heights for the equipment and the obstacles must be the top priority.

Step 3 is to create a three-dimensional near-field shading model. Here you finally input obstacles and equipment rows as shapes. In practice, at this stage it is more important to reproduce the dominant shading factors first rather than getting overly fixated on excessive detail. For example, on a rooftop, start with large parapet walls or equipment rooms, the spacing between photovoltaic equipment rows, and clearly tall obstacles. For ground-mounted installations, prioritize the front-to-back spacing of equipment rows, terrain-derived shading, and surrounding structures. Objects with ambiguous shapes, such as trees, are difficult to reproduce perfectly in practice, so it is important to take a conservative estimating approach while considering seasonal variation and canopy spread. During the input work, it is more important that the contours that cast shadows are plausibly represented than that the shapes look neat. Even if the appearance is tidy, errors such as being thinner than the real object, lower in height, or poorly positioned will reduce the reliability of the results.

The fourth step is to visualize how shadows fall and verify their validity. Don’t be satisfied with just creating the model; change seasons and times of day and check where the shadows fall. This verification work is extremely important, because input errors are hard to notice by looking at numbers alone and often only become apparent as a sense of incongruity when you observe the movement of shadows. If an obstacle that should cast long shadows in the morning is instead strongly shading at noon, or if the inter-row shading that should produce long shadows in winter is hardly visible, some position, height, or orientation may be off. In practice, simply comparing periods near the summer solstice and near the winter solstice, and morning versus afternoon, will uncover many mistakes. If you treat verification of shadow settings as more important than the initial input, the accuracy of the results will tend to be more stable.

Step 5 is to read the simulation results and revise the model as necessary. Shadow settings are not something you complete in a single pass. If there are annual losses, don’t just look at the number itself — check which months the losses are concentrated in, which times of day they are occurring, and whether changes in layout could provide room for improvement. If the losses are larger than expected, review whether obstacles are too strong, row spacing is insufficient, or the modeling assumptions are too strict. Conversely, if the losses are too small, you may have overlooked shadowing factors. What’s important here is not to adopt the results’ numbers as they are, but to judge their validity against on-site intuition. If a site clearly has noticeable shadows in the mornings and evenings during winter yet the annual shading loss is extremely small, you should suspect the model is too lenient.

What you should keep in mind through these five steps is that shadow configuration is not a data-entry task but a verification task. Gather reference materials, adjust relative positions, create the shapes, check shadow movement, and read the results to make corrections. When you can run this cycle, shadow configuration in PVSyst becomes not just an operation but a process that improves the quality of the design.

Common Mistakes and Solutions in Shadow Settings

When setting shadows in PVSyst, even if the operation itself completes, it is not uncommon for the validity of the results to be questionable. Here, we summarize common mistakes that occur in practice and explain how to address them.

The most common mistake is confusing the reference surface for obstacle heights. Especially for rooftop equipment, heights measured from the roof surface and from the ground are easily mixed, causing the relative heights as seen from the installation surface to be inconsistent. Even if this discrepancy appears small visually, it can greatly affect shadow length at low solar elevations in winter. As a countermeasure, always choose a single reference plane before entering data and align the height information for equipment and obstacles to that same reference. This alignment is particularly important when mixing values taken from drawings, on-site measurements, and estimates from photographs.

Another common issue is inaccuracy in positional relationships. Often only the approximate positions of obstacles are entered, and calculations are performed without precise distances to the equipment rows. Shadows are strongly affected not only by height but also by distance. Simply entering an object slightly farther away can significantly change shading in the morning and evening. As a countermeasure, first fix the plan positions and make sure to record at least the representative dimensions with reliable values. Before modeling fine shapes, correctly entering the center positions and the relative distances has a greater impact on accuracy.

Also, there is a failure mode where trying to model every object of concern on site makes it impossible to distinguish between major and minor factors. Work time just increases, and it becomes difficult to see which shadows are contributing to annual losses. To prevent this, it is effective to first create an initial model including only the major shading factors, and then refine it in stages as needed. Rather than aiming for a perfect three-dimensional model from the outset, it is important to grasp the dominant shading factors first.

Furthermore, the mistake of skipping verification of shadow visualization must not be overlooked. Feeling relieved after completing the input and proceeding straight to the annual calculations can lead you to trust the results without noticing reversed orientation, positional shifts, or height entry errors. The countermeasure is simple: always vary the season and time to check how shadows move. Inspect the morning, around noon, and evening, and compare summer and winter to see whether the results deviate significantly from on-site observations. If the appearance of the shadows feels off, it is important to question the model before looking at the numbers.

Another common problem in practice is looking only at the numerical results without analyzing the causes. If you focus solely on the conclusion of what percentage the annual loss is and do not examine in which months or time periods those losses occur, you will not arrive at effective countermeasures. It becomes difficult to judge whether you should widen row spacing, prioritize obstacle avoidance, or reconsider the orientation of equipment. As a remedy, check not only annual values but also monthly and seasonal trends, and identify where the causes of the losses are concentrated. If you treat the way results are interpreted as part of the shading configuration, it becomes easier to translate findings into design improvements.

How should the calculation results be interpreted

After completing the shading configuration, the important thing is not to take the output numbers at face value, but to interpret them in a way that can inform design decisions. For practitioners, what is truly needed is not a single figure stating the annual percentage of shading loss. It is to determine in which seasons those losses are concentrated, whether they stem from factors that can be mitigated, or whether they are constraints that must be accepted.

First, what I want to confirm is that shading losses are not uniform throughout the year. At many sites, shadows lengthen in the mornings and evenings during winter, causing losses to concentrate. Conversely, in summer the sun angle is higher, so the same obstacles may have a reduced shading effect. Therefore, even if the annual value is the same, the design implications differ between a case where losses are strong only in winter and a case where they act gradually throughout the year. If you consider power generation planning and its relationship with demand, it is important to look at when the losses occur.

Next, you should examine whether that shading loss can be avoided. For example, if the shading is caused by insufficient spacing between rows of equipment, it may be possible to improve the situation by changing the layout. On the other hand, if the shading is due to site conditions or existing buildings, complete avoidance may be difficult. If you compare only the loss figures without sorting out this distinction, you may waste time pursuing impractical improvement measures. In practice, it is important to separate avoidable shading from shading that must be accepted.

Also, caution is needed when the results are too small. If shadows are clearly visible on site but the simulation shows almost no shading loss, the model may be too optimistic. You should recheck the input conditions: obstacles might be missing, positions might be too far off, heights might be too low, or the orientation might be incorrect. Conversely, if the loss is too large, check whether obstacles have been overestimated for safety or whether there are unnecessary duplicate entries. Results should always be interpreted in dialogue with on-site judgment.

Furthermore, when performing comparative evaluations, attention must be paid to how conditions are aligned. If one proposal includes obstacles in detail while another is simplified, the comparison will not be fair. When comparing layout proposals, standardize — as much as possible — the meteorological conditions, equipment capacity, azimuth, tilt, and obstacle assumptions, and make it clear whether differences are due to shading settings or to layout differences. If the premises for comparison are not aligned, you may think you have chosen the better option, but in reality you are merely looking at differences in input accuracy.

When interpreting calculation results, it is essential to maintain the perspective of ultimately translating numbers into decision-making. It is not about how much shading loss there is, but only when you consider whether to accept that loss, avoid it, and—if you choose to avoid it—what to change, that PVSyst’s results become useful in practice. Shading configuration is not a task to produce numbers, but a task to provide a basis for design decisions. Simply adopting this mindset will greatly change how you read the same result tables.

Practical Steps to Improve the Accuracy of Shadow Settings

If you want to improve the accuracy of shadow settings, it is more effective to review how you collect and organize on-site information than to focus on the software operation itself. This is because shadow models depend heavily on the quality of their input data. No matter how carefully you create shapes on the screen, if the underlying dimensions and positional relationships are ambiguous, the reliability of the results will be limited.

In practice, if you first organize on-site obstructions into four categories—"height", "width", "distance from the mounting surface", and "elevation difference relative to the mounting surface"—it becomes less likely that information needed for shadow settings will be omitted. Even when shapes are complex, covering these four elements makes it easier to model the primary effects on shadows. In particular, distance and elevation difference are easily misidentified from photos alone, so if possible verify them on site to keep accuracy stable. For existing roof projects, parapets or the upstand of equipment foundations can be higher than expected, so it's safer not to rely solely on drawings.

Also, before inputting data it is useful to identify the directions that are likely to cast strong shadows. Rather than paying equal attention to all orientations, first check the directions that are prone to casting shadows during times when the sun’s altitude is low in winter, the side where adjacent obstructions are concentrated, and the side likely to produce long shadows in the morning and evening. This makes it easier to decide which obstructions should be prioritized for refinement. In practice, even this prioritization alone can greatly affect work efficiency.

It is also important not to separate layout planning from shadow settings. Shadow settings are often regarded as a post-layout checking task, but in fact they should be used to judge the merits of layout proposals. Considerations such as slightly increasing row spacing, avoiding locations near obstacles, or fine-tuning the orientation of equipment groups only make sense when carried out together with shadow settings. If shadow settings are used only to verify the final plan, it becomes difficult to change the design even when there is room for improvement.

What I recommend for practitioners is to first grasp trends with a simplified model and then detail only the primary option. In the initial stage, check approximate shading losses using only the major obstacles, and once candidates are narrowed down, refine them with a detailed model. This two-step approach lets you secure the necessary accuracy while reducing work time. It makes it easier to balance the speed and quality of decision-making than creating a detailed model from the outset.

Moreover, what is indispensable for further improving the quality of shadow settings is the accuracy of on-site measurements. Elevation differences and obstacle positions that are hard to grasp from drawings and photographs alone become much easier to incorporate into a three-dimensional model if coordinates and heights are measured on site with high precision. This is especially true for sites that include roofs, graded land, or slopes, where the visual impression often differs from actual elevation changes. In such cases, having a method to capture positions accurately on site helps keep the assumptions behind the shadow settings stable.

Summary

When setting shadow effects in PVSyst, what matters more than memorizing screen operations is organizing the causes of the shadows, aligning their relative relationships with the installation conditions, always verifying with visualization after creating a three-dimensional model, and linking the results to design decisions. As five steps to avoid failure, if you follow the flow of identifying shadow factors, organizing installation conditions and coordinate relationships, creating a nearby shading model, checking the movement of shadows, and making adjustments after reviewing the results, the accuracy of shadow settings will become much more stable. In particular, it is important to understand that shadow setup is not a one-time input task but an iterative verification process refined by comparing on-site intuition with the results.

In practice, the accuracy of shading settings is determined by the quality of on-site information. If the heights and positions of obstructions and the elevation differences relative to equipment surfaces remain ambiguous, no matter how carefully you build the model the reliability of the results will not improve. That is why how efficiently and precisely on-site verification is carried out before and after design dictates the quality of power generation simulations. If you want to obtain site coordinates and heights quickly and accurately, using an iPhone-mounted high-precision GNSS positioning device such as LRTK makes it easier to identify obstruction locations and candidate installation sites. To raise simulation accuracy, the shortcut is not just desktop settings but making on-site data acquisition high-precision. The more practitioners struggle with shading-setting accuracy in PVSyst, the more reviewing the process from the site-measurement stage will help lead to more convincing design decisions.