What is PVSyst? An easy-to-understand explanation of its features, including shading analysis

Table of Contents

• What is PVSyst?

• Why PVSyst is used in practice

• Main functions of PVSyst

• Basic usage of PVSyst

• Key concepts to understand for shading analysis in PVSyst

• Procedure for conducting shading analysis in PVSyst

• How to interpret simulation results

• Points to note when using PVSyst

• Roles suited for using PVSyst

• Summary

What is PVSyst?

PVSyst is simulation software that can handle the entire photovoltaic power generation system workflow—from system design and sizing to performance evaluation and operational data analysis. It is not merely a calculator for roughly estimating annual energy production; a major feature is that it enables evaluation by linking site conditions, meteorological conditions, module surface orientation, system components, various losses, shading effects, and result analysis in a single workflow. In its official documentation, it is positioned as software for performing detailed studies and data analysis for multiple system configurations such as grid-connected, standalone, pumping applications, and DC systems.

When practitioners search "What is PVSyst," it's often because they've only heard the name and it's unclear what it can actually check and to what extent. To be clear, PVSyst is not just a tool for power production forecasting. It is an evaluation platform for organizing project conditions, comparing multiple proposals, examining the breakdown of losses, and, when necessary, comparing results with actual measurements. Its strength lies in allowing you to dig one level deeper than simple estimation tools, especially for projects where you want to carefully verify the validity of the design and the effects of shading.

When trying to understand PVSyst, it is important not to think of it as "software that answers a system's performance with a single point." In reality, it is software for assembling assumptions and comparing them across multiple patterns while tracking where the differences in results come from. In other words, its practical use lies in the entire examination process that leads to the final numbers, rather than the moment those final numbers are produced. With this perspective, PVSyst's functions appear not as a mere collection of menu items but as a mechanism that supports design decision-making.

Why PVSyst Is Used in Practice

One reason PVSyst is highly valued in practical work is that it makes it easy to organize the assumptions for each project. The official documentation describes a project as a framework that contains geographic location and time-based meteorological data, within which multiple variations can be created for optimization and comparison. This is very important in practice, because in the field you frequently need to compare scenarios such as “what happens if we change the tilt angle slightly,” “what if we change the azimuth,” or “how much difference is there between including shading and not including shading.” PVSyst treats these comparison tasks not as one-off jobs but as extensions of the same project conditions, which makes it less likely that assumptions will get confused.

Another reason is that the way results are presented is practical for field use. Rather than stopping after reporting only annual energy production, the loss diagram lets you visually track where energy is being lost. Moreover, because you can check the impact of losses not only on an annual basis but also month by month, it becomes easier to grasp seasonal differences—whether the impact is greater in winter or whether temperature-related losses in summer are significant. The fact that it is easy to use not only for technical staff but also as material for internal presentations and explanations to clients or project owners about “why this proposal is reasonable” is why PVSyst has been used for so long.

Furthermore, one of PVSyst’s strengths is that it connects the study phase through to operational analysis. By importing measured data and enabling close comparisons with simulation results, it can be used not only for pre-construction predictions but also for post-construction verification. In practice, if the design and operation phases are treated separately, the underlying assumptions can become disconnected and root-cause analysis becomes difficult. In that respect, PVSyst allows design values and measured values to be compared within the same context, making it useful for identifying causes of under-generation and for considering possible adjustments to settings.

Main features of PVSyst

When summarizing PVSyst's main functions, the central feature is the project design capability. You set the site, meteorological data, and, if needed, ground reflectance conditions, and then build up the panel orientation, system configuration, loss factors, and shading conditions. The official documentation explicitly defines a structure whereby multiple variations are created for a project and simulations are run for each. This can be described as a design philosophy based on comparing multiple options rather than performing a single-run calculation.

Another important aspect is the handling of meteorological data. In PVSyst, you can not only start your analysis from the meteorological database, but also flexibly import custom meteorological and operational data. The official help explains that measured data at hourly or finer time resolutions can be imported in a fairly wide range of text formats. The data-quality-check functions recommend verifying time offsets, the absolute magnitudes of values, and anomalous values. In other words, PVSyst is not just software for entering data; it prompts users to consider the validity of the input data. Because power generation simulations will vary when inputs fluctuate, this function, though modest, is quite important in practice.

The range of supported system types is broad: it can handle not only grid-connected systems but also stand-alone, pumping applications, and DC systems. Furthermore, because it can handle systems that include self-consumption and energy storage, it does not end with generation—you can see where energy is used, where it flows, and where constraints are imposed. Depending on the nature of the project, the self-consumption rate and behavior under grid constraints can be more important than the amount of generation, so this breadth of coverage provides reassurance in practice.

In terms of result analysis, loss diagrams, performance ratio, monthly, daily and hourly results, parametric studies, P50/P90 evaluations, and comparisons with measured data are all available. For example, the batch feature lets you run simulations collectively while changing multiple parameters and compile the results in a list. This makes it easier to review options while comparing tilt angle, spacing, shading conditions, loss settings, and so on. Additionally, the P50/P90 evaluation is performed by setting additional uncertainties after the initial simulation, enabling assessments that go beyond simple power generation forecasts to consider the range of predicted outcomes.

The shading analysis mentioned in the title is a key feature that defines PVSyst. It offers methods to treat distant obstacles as a horizon profile, to model nearby obstacles as a 3D scene, and even to investigate electrical mismatch caused by partial shading. By going this far, you can organize not just the simplistic explanation "it decreases because there is shading," but rather "which shadow at which times translates into what kind of loss." This is precisely why it is worthwhile for practitioners to learn PVSyst.

Basic Usage of PVSyst

The basic workflow in PVSyst starts with building the foundation of a project. Specifically, you create a project that contains the site location and meteorological data, and within that project you create variations for comparison. Understanding this structure makes it clear that PVSyst is not just calculation software but an evaluation tool with project-management capabilities. Common practical comparisons—such as changing only the tilt angle or shading conditions at the same site, or reviewing only the loss settings on the same layout—become easier to carry out in an organized way.

Next, you set the panel surface orientation and the system configuration. PVSyst includes support functions to check orientation optimization, allowing you to see how much the chosen tilt angle and azimuth differ from the optimal conditions. Because both a simple evaluation and a more detailed evaluation based on hourly meteorological data are provided, you can use a coarse approach in initial studies and a high-precision approach in the finalization stage. What is important here is not to mechanically select the optimal solution but to judge, in light of site conditions and racking conditions, how far you can compromise and what you cannot compromise on.

After that, set the system configuration and the detailed losses. According to the official documentation, within the system definition you define the modules, strings, power conversion equipment, and the grid connection, and on a separate screen you can adjust detailed losses such as soiling, incidence angle correction, temperature, wiring resistance, quality differences, mismatch, and downtime. If you run with these at their default values, the calculations may appear to complete, but the results will not withstand practical use. Conversely, PVSyst is software whose ability to explain results increases the more carefully you account for these losses.

If the project does not involve shading, you can run simulations with the settings up to this point. However, if the effects of surrounding terrain, buildings, fences, trees, elevation differences, row-to-row shading interference, etc. cannot be ignored, proceed to the horizon or near shading settings. For layouts that are strongly affected by partial shading, you will use functions to define module placement and circuit connections. In other words, understanding that PVSyst’s basic operation is not about filling in input fields in order but about modeling to the depth required by the project’s complexity will make it much easier to use.

Key Concepts to Keep in Mind for Shading Analysis in PVSyst

When understanding PVSyst’s shading analysis, the first thing to grasp is that shading exists on at least two levels. One is shading from distant obstacles — a type that affects the entire power-generating surface almost uniformly at a given moment, such as mountain ranges or distant clusters of buildings. The other is shading from nearby obstacles, where nearby buildings, trees, parapets, equipment, the same row or adjacent rows, etc., cast specific shadows on parts of the power-generating surface. The official documentation explains that distant shading can be handled relatively simply with a horizon profile, whereas nearby shading requires a full 3D representation of the shapes.

The reason for distinguishing far-field shadows from near-field shadows is that the calculation approaches differ. Far-field shadows are treated more like whether the sun is visible or not for the entire power-generating surface, and are defined by overlaying the horizon line onto the sun-path diagram. In contrast, near-field shadows are calculated in 3D space to determine which obstacle is at which position and where its shadow falls at what times. Official documentation states that far-field shadows are generally appropriate for obstacles located roughly ten times the characteristic size of the power-generating surface or farther, and that closer obstacles should be handled as near-field shadows. Confusing these approaches can easily lead to shadow estimates that are either too large or too small.

Furthermore, what makes PVSyst's shading analysis suitable for practical use is that it does not treat shading as merely an area issue. The official documentation explains that during simulations the shading calculation is performed for each time step and applied separately to direct irradiance, diffuse sky irradiance, and ground-reflected irradiance. In other words, it looks at the impact not only of whether the sun's direct beam is blocked but also of light scattered from the sky and reflections from the ground. This is a major difference from beginners who think of shading analysis only in terms of whether shadows occur in the morning or evening. In PVSyst, the basic approach is to consider not simply the presence or absence of shading but to what extent each component is affected.

Going one step further, PVSyst distinguishes between linear shading and electrical shading. Linear shading is an approach that treats the loss of incident energy due to shading as a reduction in overall irradiance. Electrical shading, on the other hand, is an approach that examines how partial shading causes non-uniform power generation within circuits and increases mismatch losses. According to the official documentation, features for defining module layout and string connections allow detailed calculation of electrical shading mismatch losses. Because of this, PVSyst’s shading analysis can be said to be closer to an analysis of the mechanisms of power reduction rather than a simple calculation of shaded area.

Procedure for performing shading analysis in PVSyst

When progressing with shading analysis in PVSyst, first decide whether to create a 3D near-shading scene. If surrounding obstacles are distant and affect the entire site almost uniformly, a horizon profile may be sufficient, but if there are local shadows from buildings, trees, equipment, elevation differences, or inter-row shading, constructing a 3D scene is necessary. The official tutorial and help guide explain how to open the 3D editor from the near-shading dialog and assemble the generation surfaces and obstacles. From a field perspective, this stage is not about "thinking about shadows" but about "capturing the site in a form that allows shadows to be calculated."

Next, it is important to properly align the 3D scene with the system definition. The official documentation clearly states that if the orientation in the scene does not correspond to the system-side orientation, or if the effective area or number of modules do not match, the simulation cannot be run. In practice, many people stumble at this point. No matter how carefully you build the 3D scene, it is meaningless unless it matches the electrical configuration. Shade analysis does not end with geometry alone; it only becomes valid when it is consistent as a power generation system.

Furthermore, for projects where the impact of partial shading is important, you proceed to define the module layout and circuit connections. The official documentation explains that this feature is meant to define each module’s position and which string or input it belongs to, and to calculate in detail the mismatch losses caused by electrical shading. In other words, even the same shading can produce different losses depending on how it spans circuits. If the column arrangement is regular and the shading pattern is simple, simplification may be possible, but when you are responsible for the evaluation results, it is safer to model the connection relationships as closely as possible to the actual installation.

The more you want to improve the accuracy of shadow analysis, the more important the accuracy of the input shape information becomes. If the positions, heights, widths of obstacles, row spacing, rack tilt, or steps in the terrain are ambiguous, you may be able to run the simulation itself, but the meaning of the results will be diminished. PVSyst can handle shadows in considerable detail, but it is also software that is highly sensitive to input accuracy. Therefore, if you are serious about shadow analysis, it is important to model the site after obtaining as accurate an understanding as possible of the on-site spatial relationships and dimensions, rather than simply placing numbers on a desk.

How to Interpret Simulation Results

When reviewing results in PVSyst, the first thing you should pay attention to is the loss diagram. The official documentation also positions the loss diagram as a means to quickly identify weaknesses in system design. What’s important here is not to stop at the final energy production figure alone. By distinguishing whether shading is large, temperature effects are strong, or wiring and mismatch losses are higher than expected, the corrective measures you take will change. The value of PVSyst lies not in producing a single number, but in showing structurally how the figures decline.

In projects where shade analysis has been performed, it is especially important to read the results by separating "linear losses due to shading" and "electrical shading losses." The former is a deficiency in incident energy, while the latter is a circuit-level loss caused by partial shading. Mixing the two makes it harder to see what needs to be improved. If linear losses are large, you need to reconsider the layout and obstacle conditions. If electrical shading losses are large, there is room to review how circuits are segmented, module placement, and any bias in how shadows fall. The point of using PVSyst is that it enables this separation.

Performance ratio is also an important metric, but it is essential not to rely on it in isolation. The official documentation describes the performance ratio as the ratio of effective energy to incident energy and nominal output, and its treatment in the definition differs for grid-connected, including self-consumption, standalone, and pump applications. Therefore, it is dangerous to simply compare projects of different system types side by side. In PVSyst, the performance ratio is only one facet of the results and becomes meaningful only when interpreted together with the loss diagram and time-based behavior.

Also, if you want to be mindful of uncertainty in power generation, P50/P90 evaluations are also useful. However, as the official documentation states, these are a mechanism for evaluating the initial simulation results by additionally assuming meteorological variability and other uncertainties. In other words, P50/P90 are not magic numbers that automatically produce the truth; they are analysis results that change depending on how the assumptions are set. In practice, it is dangerous to say only “P50 so it’s safe” or “P90 so it’s conservative” without understanding this point. Before focusing on the numerical values, you should confirm what kinds of uncertainties were estimated and how.

Precautions when using PVSyst

One of the primary precautions when using PVSyst is the quality of the input data. Being able to import meteorological and measured data is a major advantage, but if the data themselves contain time shifts, unit inconsistencies, calibration offsets, or outliers, both the simulation results and any comparison results can be easily distorted. The official documentation also states that checking timestamps, absolute values, and anomalies is important. PVSyst is feature-rich, but it is not overly tolerant of its inputs; on the contrary, the more properly you use it, the more clearly the importance of input quality becomes apparent.

Another thing to watch out for is insufficient detail in the shadow model. When people think of shadow analysis, they tend to assume that creating a plausible shape in a 3D view is enough, but in reality the dimensions and positions of obstacles, relative heights, consistency of orientation, and accurate reproduction of row layouts determine the results. Moreover, if the 3D scene and the system definition do not match, the calculation itself cannot be performed. Shadow analysis is difficult not only because the calculations are complex, but because both geometric and electrical information must be correctly aligned.

The third point to note is not to focus only on annual totals. The official documentation also shows that loss charts can be checked by month, and the result files retain monthly and hourly values. Because shading often concentrates in specific seasons or times of day, relying on annual values alone can lead to misinterpretation of the actual situation. For example, even if the annual difference looks small, if there is a large drop concentrated in winter mornings and evenings, the alignment with the demand side and the operational implications change. If you want to make practical use of PVSyst, you need to develop the habit of looking at the annual total together with the temporal distribution.

The fourth point is: do not use P50/P90 merely as convenient labels. As the official documentation makes clear, this evaluation requires assumptions about uncertainties that cannot be provided by simulation alone. Therefore, when explaining generation forecasts internally or externally, you need to describe not only the P50 and P90 figures but also which types of meteorological data were used and what ranges of variability and uncertainty were assumed. Being able to explain the assumptions behind the numbers, rather than the numbers themselves, is what builds trust in practice.

Who PVSyst is Suitable For

PVSyst is suited to those who want to evaluate solar power projects not as simple rough estimates but while organizing the underlying assumptions. For example, for designers it is useful that orientation, row layout, shading, and the buildup of losses are easy to organize. From the perspective of technical review, the ability to trace which assumptions led to which results is helpful. From an operations and maintenance perspective, the comparison function with measured data makes it easier to investigate causes of underproduction or behavioral discrepancies. In short, PVSyst is suitable—regardless of department—for people who need to connect assumptions and results.

Conversely, in situations where you only want a rough estimate in a few minutes, or where you just want to broad trends without delving deeply into shading or losses, you may not be able to make full use of PVSyst’s strengths. PVSyst is software that shows its true value when you carefully prepare inputs, compare multiple scenarios, and read into the breakdown of the results. That is why, when asked “what is PVSyst?”, I prefer to describe it not merely as a power-generation simulator but as an analysis environment that supports design decisions for solar PV projects. With this perspective, it becomes easier to see which functions you should learn and the situations in which you should use it first.

Summary

PVSyst is a professional simulation software for performing end-to-end design, loss assessment, and result analysis of photovoltaic power generation systems. Based on site and meteorological data, it allows comparison of multiple variations, interpretation of results using loss diagrams and performance ratios, and, where necessary, progression to comparisons with measured data and P50/P90 analyses. Among its features, shading analysis is particularly in-depth, covering far-field shading, near-field shading, and electrical mismatch; as such, the level of understanding of PVSyst is directly reflected in the accuracy of the study in this area. Once you master it including shading analysis, you will be able to explain why a given energy production figure occurs, rather than focusing solely on the number itself.

And to truly make use of PVSyst’s shading analysis, it is essential to capture on-site positional relationships and obstacle geometries as accurately as possible. This is because near-field shading calculations require an accurate 3D reproduction of the PV array surface and the surrounding environment. If you want to streamline on-site coordinate acquisition and obstacle-position mapping, using a smartphone-mounted high-precision GNSS positioning device such as LRTK to record site and equipment positions with high accuracy before importing them into PVSyst will make it easier to improve the reproducibility and explanatory power of the shading analysis. The more practitioners want to raise the accuracy of desk simulations, the more important it is to pay attention to the accuracy of field measurements.