6 Basic Module Settings Learned from the PVSyst Manual

Table of Contents

• The importance of learning module configuration in the PVSyst manual

• Basic 1: Understand the role of the module database and the PAN file

• Basic 2: Correctly verify manufacturer specification values and STC conditions

• Basic 3: Check size, cell configuration, and bypass diodes

• Basics 4: Viewing temperature coefficient and low-light characteristics from a practical perspective

• Basic 5: Organize module quality, mismatch, and IAM losses

• Basic 6: Check the impact on string configuration and inverter selection

• Common Mistakes in Module Configuration and the Verification Process

• Summary

The Importance of Learning Module Configuration from the PVSyst Manual

When performing energy yield simulations of a solar power generation system using PVSyst, the first thing to be mindful of is the module settings. There are many conditions that affect energy production—weather data, azimuth, tilt, shading, losses, and inverters, among others—but the starting point for generation is the photovoltaic module itself. How you handle the module’s output, voltage, current, temperature characteristics, cell configuration, area, and loss conditions will change the annual energy yield, PR, loss diagram, and the comparison results of design proposals.

Reading the PVSyst manual makes it clear that module configuration is not simply a matter of selecting a model number, but a linked process involving the database, PAN files, manufacturer specification values, model parameters, size, technical information, and loss settings. In PVSyst’s PV Module screen, tabs are provided for Basic Data, Size and Technology, Model Parameters, Additional Data, Measured Data, Commercial Data, Graphs, and so on, forming a structure that allows management of the module’s electrical and physical characteristics.

What beginners particularly tend to stumble over is assuming that simply selecting a module will automatically produce entirely correct calculations. PVSyst has an extensive module database, but you must verify that the model number you plan to use for the project, the datasheet version, output tolerance, temperature coefficient, cell configuration, whether it is bifacial, module area, and so on, actually match the design conditions. Even if the database contains a model number that is similar, it may not have exactly the same specifications, so when using it for design, costing, or feasibility assessment, cross-checking with the manufacturer's datasheet is essential.

Also, PVSyst simulations are closely tied to the system configuration — which module, how many modules, how they are arranged in strings, and which inverter they are connected to. If module settings are incorrect, they will affect the string voltage range, the oversizing ratio, clipping, reduced output at higher temperatures, open-circuit voltage at low temperatures, loss evaluation, and so on. In other words, module configuration is not a parts-registration task but a task that determines the assumptions for the entire energy-yield simulation.

This article breaks down the basic module settings you should check in the PVSyst manual into six parts. Aimed at people who are just starting with PVSyst, those unsure whether they can reuse existing data, and those who want to validate their simulation results, it focuses on practical points that are often overlooked.

Basic 1: Understand the roles of the module database and PAN file

When handling photovoltaic modules in PVSyst, the first thing to grasp is the relationship between the module database and PAN files. In PVSyst, various module parameters are stored as component data, and that data is selected and used during system design. On the module basic data screen, manufacturer name, model name, data source, file name, and so on are managed, and the file name is an important item related to identification within the database. In PVsyst's documentation, PV module files are treated as having the extension ".PAN" and are described as information that uniquely identifies them within the database.

A PAN file is not simply a memo of a product name. It is component data that contains the assumptions used for simulations, such as output, voltage, current, temperature coefficients, cell configuration, area, and model parameters. Therefore, caution is required when reusing PAN files from past projects as-is. Even similar part numbers from the same manufacturer may differ in cell size, output range, electrical characteristics, output tolerances, temperature coefficients, and conditions for bifacial power generation. Just because part numbers look similar does not mean they will be the same in power-generation simulations.

In practice, you often select modules already registered in PVSyst, but when making a selection it is important to at least verify the manufacturer name, model number, rated output, Vmpp, Impp, Voc, Isc, temperature coefficients, and module dimensions against the datasheet. In particular, selection mistakes are more likely when the datasheet has been updated or when there are multiple power classes within the same series. For example, if the same series includes models such as 400 W, 405 W, and 410 W, the names may look similar but the voltages and currents can differ slightly. Even if those differences seem small, they can affect annual energy yield and DC capacity at plants with thousands or tens of thousands of modules.

The benefits of using a module database are that it reduces input work and that the parameters required by the PVSyst model are organized. On the other hand, if you trust registered data unconditionally, it may diverge from the latest specifications adopted for a project. When reading the PVSyst manual, it is easier to understand if you separate the task of selecting from the database from the task of checking whether the selected data matches the project’s conditions.

When creating a new module or duplicating and modifying existing data, be sure to check the source of the original data. Reliability varies depending on whether it was created from the manufacturer's datasheet, reflects measured values, or is merely an edited older model. In design reviews, keeping a record not only of the PVSyst configuration screens but also of the version of the datasheet used, the rationale for the PAN file you created, and the items you changed will make later verification easier.

Basic 2: Correctly verify manufacturer-specified values and STC conditions

The most fundamental aspect of module configuration is verifying the manufacturer's specification values. In the PVSyst manual, the manufacturer's specification values are described as the module's main electrical characteristics and are typically given under STC conditions. STC refers to the standard test conditions that generally define irradiance, cell temperature, and spectral conditions, and serve as a reference for comparing a module's rated output and electrical characteristics. In PVSyst, a module model is constructed based on the manufacturer's specification values, and the power generation behavior under various irradiance and temperature conditions is calculated.

What is important here is not simply entering the numbers listed in the datasheet, but understanding what each of them means. Typical items to check are Pmax, Vmpp, Impp, Voc, Isc, output tolerance, and temperature coefficient. Pmax is the maximum power; Vmpp and Impp are the voltage and current at the maximum power point; Voc is the open-circuit voltage; and Isc is the short-circuit current. These are indispensable for string design, inverter selection, the oversizing ratio, low-temperature voltages, and reduced output at high temperatures.

One thing to be especially careful about is not to judge a module solely by its rated output. For example, even among modules in the same 550 W-class, some are designed with higher voltage and lower current, while others have higher current. Compatibility with the inverter's MPPT input range, maximum input current, and allowable short-circuit current cannot be judged by output alone. To create a correct system definition in PVSyst, you need to confirm the module's voltage and current characteristics together.

The numerical values under STC are not representative of actual operating conditions. Outdoors, solar irradiance fluctuates, cell temperature rises, and modules are affected by wind, mounting configuration, rear-side ventilation, racking conditions, soiling, and shading. Therefore, STC output indicates the module’s reference performance and does not mean that such output will be achieved continuously throughout the year. PVSyst estimates annual energy production by taking the module characteristics defined at STC and combining them with meteorological data, temperature models, and loss conditions.

Also, the handling of output tolerance is an easily overlooked point. In module datasheets, the output tolerance may be indicated with a ± notation or with a notation that shows only the positive side from 0. In PVSyst there is a concept that the initial value of the module quality loss is related to the output tolerance, and, for example, the treatment differs between a tolerance like ±3% and a positive-side tolerance like 0 to +3%. In PVsyst's documentation, module quality loss is described as a parameter representing the confidence in the actual module performance relative to the manufacturer's specifications, and the initial value is explained to be set based on the module's output tolerance specification.

When checking module settings in PVSyst in practice, don’t just compare the datasheet values with the PVSyst input values; also verify the units, conditions, version number, and output class. If you refer to old datasheets, specifications for other regions, or documents with different cell configurations, the numbers may be slightly off. The reliability of power generation simulations is determined by the accumulation of these small assumption checks.

Basic 3: Check the size, cell configuration, and bypass diodes

In module settings, not only electrical characteristics but also size and cell configuration are important. The PVSyst manual states that module size should be defined because it forms the basis for calculating module efficiency, and the number of series cells is important because the single-diode model is constructed based on cells and is necessary for PVSyst to derive the cell voltage from the module's STC values.

Module dimensions are not merely information for layout drawings. Changes in module area affect module efficiency, installation density, land use, capacity per roof area, shading assessment, and placement in 3D scenes. For ground-mounted projects they influence row spacing, GCR, the occurrence of shading, and the configuration of racking tables; for rooftop projects they affect allocation to roof surfaces, aisles, clearances, and considerations for fire and maintenance space. If dimensions are incorrect in PVSyst, not only the electrical energy yield but also the number of modules that can be installed and the assumptions about shading will be off.

Cell configuration has also become increasingly important in recent years. Module structures are diversifying beyond conventional crystalline modules to include half-cut cells, multi-busbar designs, bifacial power generation, N-type cells, and large-format cells. In PVSyst calculations, not all product-specific structures are reproduced in full detail, but the number of cells, sub-module configuration, and the concept of bypass diodes are important for understanding partial shading and electrical impacts.

Bypass diodes, in particular, are an item you want to check on projects with partial shading. When part of a module is shaded, the shaded cells or substrings limit the current, causing reduced power output and creating hotspots. Bypass diodes help mitigate these effects, but how losses appear depends on the location of the shading, the cell connections, the module orientation, and the string configuration. When handling 3D shading or module layout in PVSyst, it is important to decide how much of the module’s internal structure to model.

The standard module model in PVSyst is based on a single-diode model that represents the behavior of PV cells. In PVSyst’s documentation, it is stated that this model was developed for a single cell and that, when generalized to the entire module, it assumes all cells are identical. In other words, correctly understanding the module structure also leads to understanding the model’s assumptions and limitations.

In practice, the basic procedure is to check the module size, number of cells, number of bypass diodes, portrait/landscape orientation, and substring configuration on the specification sheet and confirm they do not deviate from the values registered in PVSyst. In particular, for rooftop projects with shading, ground-mounted projects that receive shadows from fences or the front rows of racking, and projects that place modules on roofs with multiple orientations, it is important not to overlook the relationship between module orientation and cell wiring.

Basic 4: Examining Temperature Coefficients and Low-Light Characteristics from a Practical Perspective

In PVSyst's module settings, temperature characteristics are a major factor affecting energy production. Solar cell modules generally see output decrease as cell temperature rises. Temperature losses tend to be larger in high-temperature regions, for roof-mounted installations, and under poorly ventilated installation conditions, which affects annual energy yield and summer peak output. Therefore, the temperature coefficient must be correctly checked in the module settings.

In datasheets, the temperature coefficient of Pmax, the temperature coefficient of Voc, and the temperature coefficient of Isc are typically specified. The Pmax temperature coefficient indicates how much the maximum power decreases when the cell temperature rises. The Voc temperature coefficient is important for checking the open-circuit voltage at low temperatures. In cold climates, as module temperature drops Voc rises, so if the number of modules in a string is too high there is a risk of exceeding the inverter’s maximum input voltage. The Isc temperature coefficient relates to changes in short-circuit current and is useful as a reference when checking input current.

Temperature coefficients affect not only energy yield but also safety design. For example, increasing the number of modules in a string just to raise the rated output can cause the Voc at low temperatures to exceed the inverter’s allowable voltage. Conversely, in hot summer conditions Vmpp can decrease and approach the lower limit of the MPPT range. When defining the system in PVSyst, you should not treat the module and inverter settings separately; it is necessary to check the voltage range including temperature conditions.

Low-irradiance characteristics are also easily overlooked. Solar power systems do not always operate under strong sunlight. Morning and evening, overcast days, after rain, during winter, and in shaded periods, operation under low-irradiance conditions is not uncommon throughout the year. Depending on how a module's low-irradiance efficiency is represented in the simulation, the estimated annual energy yield can change. PVSyst's PV module screen also provides measurement-data tools for handling low-irradiance efficiency and measured I-V curves.

However, low-irradiance and temperature characteristics cannot fully represent actual site conditions based solely on the values in the datasheet. They are influenced by installation conditions, ventilation, backside temperature, racking configuration, roofing material, ambient temperature, wind speed, snow accumulation, soiling, and other factors. When interpreting the energy yield calculated by PVSyst, you need to check the module parameter values themselves together with the temperature model and the installation-condition settings.

In practice, it is important not to underestimate differences in temperature coefficients between modules. Even within the same power class, temperature coefficients vary by cell technology and manufacturer. In hot regions and rooftop projects, it is important not only to choose modules with high rated power but also to compare how much output drops at high temperatures. When comparing multiple module candidates in PVSyst, looking beyond simple DC capacity to include temperature losses, generation under low irradiance, and compatibility with the inverter will lead to decisions that are closer to real-world practice.

Basic 5: Organize module quality, mismatch, and IAM losses

Understanding the loss items is indispensable when linking PVSyst module settings to energy yield assessment. In particular, module quality loss, mismatch loss, and IAM loss are closely related to module characteristics. In PVSyst’s system definition, the PV array losses are structured so that parameters such as thermal losses, wiring resistance, module quality, mismatch, IAM, and downtime can be modified. These have default values set, but they need to be checked according to the project conditions.

Module quality loss is a parameter that indicates how much the actual module performance can be trusted relative to the manufacturer's specified values. In PVSyst's description, this is a user-definable parameter and can be used, for example, to allow a margin for warranties. Furthermore, it is suggested that the initial value be set based on the module's power output tolerance specifications.

One thing to be careful about here is not to leave module quality loss at the default value simply because you don't understand it well. Default values are convenient, but they don't necessarily align with the intent of the project. Whether it's a conservative energy-yield assessment for a financial institution, a comparison at the preliminary design stage, an EPC estimate, or a post‑O&M performance comparison, the way losses are treated will vary. If modules have output tolerances only on the positive side, the handling of quality losses may also change. Designers need to be able to explain why they adopted a given loss value, not just state the loss value itself.

Mismatch loss is the loss that occurs because the I-V characteristics of modules within the same string or array do not perfectly match. In PVSyst’s description, mismatch loss is defined as the difference between the sum of the Pmpp of each individual submodule and the Pmpp obtained from the synthesized array’s I-V characteristic. In practice, factors such as manufacturing variability, aging, soiling, shading, temperature differences, and variations in conditions between strings contribute.

Mismatch loss may appear small numerically, but it is not negligible for the whole plant. In particular, when there are multiple orientations, multiple tilts, partial shading, mixing of different module lots, mixing of replacement modules, or similar conditions, you should verify whether a simple uniform value is appropriate. When you handle module layout and electrical shading in detail in PVSyst, understanding the concept of mismatch makes it easier to interpret the loss diagram.

IAM loss is the reflection loss caused by the angle of incidence. The more the sunlight strikes the module surface at an oblique angle, the greater the reflection at the glass surface and the less light is available for power generation. In PVSyst, IAM loss is treated as part of the array losses. PVsyst's documentation states that when setting a manufacturer-specific IAM profile for a module in the database, a detailed measurement report from an independent laboratory is required. It also explains that, for bifacial systems, the IAM loss on the rear side is calculated using a specific model.

IAM losses are a factor to be mindful of in situations with a lot of low-angle sunlight, such as mornings and evenings, winter, high-latitude locations, and low-tilt installations. Differences may also arise depending on module glass specifications, anti-reflective coatings, and surface structure. However, when using manufacturer-specific data, the measurement basis is important. Unsupported optimistic IAM settings can lead to overestimation of energy yield.

Module quality, mismatch, and IAM may appear as independent items, but in practice they relate to how conservatively margins are set, which affects the reliability of the energy yield. When reading the PVSyst manual, it is important to understand the definitions of each loss item and to decide, according to the project's objectives, whether the default values are acceptable, whether they should be set more conservatively, or whether they should be adjusted based on measurements or manufacturer documentation.

Basic 6: Verify the impact on string configuration and inverter selection

Module configuration does not end with entering the performance of a single module. At the stage of defining a system in PVSyst, you decide how many modules to arrange in series and in parallel, and which inverter to connect them to. In PVsyst’s grid-connected system definition, the system is described as a PV array, that is, a configuration consisting of PV modules, strings, inverters, and the grid connection.

When configuring strings, the first thing to check is the voltage range. Verify that the Voc at low temperature does not exceed the inverter's maximum input voltage, and that the Vmpp at high temperature does not fall below the lower limit of the MPPT range. Increasing the number of modules raises the string voltage, while decreasing the number of modules lowers it. The appropriate number of modules is determined by the module's Voc, Vmpp, temperature coefficient, local temperature conditions, and the inverter's input specifications.

Next, you need to check the current. Many recent high-output modules have large currents, so compatibility with the inverter's maximum input current and short-circuit current rating has become important. Even if you can assemble the system in PVSyst, you must always verify that there are no issues with the actual equipment specifications. In particular, the number of parallel strings, the number of inputs per MPPT, the overloading ratio, backfeed prevention, and the specifications of protective devices must be checked not only for PVSyst's energy-yield calculations but also from the perspective of electrical design.

The DC/AC ratio is also related to module configuration. Increasing module output raises the DC/AC ratio for the same inverter capacity and increases energy yield, but during periods of high solar irradiance the inverter may impose output limits (clipping). In PVSyst, you can evaluate the impact of such clipping through the system definition and loss assessment. However, the optimal DC/AC ratio varies depending on the design objectives; it must be considered together with factors such as feed-in tariff, grid constraints, available installation area, module unit cost, inverter capacity, and maintainability.

In string configurations, handling multiple orientations and multiple tilts is also important. In roof projects, east- and west-facing surfaces, south-facing surfaces, and low-tilt surfaces may coexist. Even in ground-mounted installations, orientation and tilt can vary due to terrain and racking layout. Grouping modules with different orientations or tilts into the same MPPT can cause losses due to differences in generation characteristics. In PVSyst, organize the definitions of sub-arrays and orientations, and verify that the configuration is electrically sound.

Also, whether shaded and unshaded areas are mixed within the same string affects energy production. If a partially shaded module limits the current of the entire string, losses can be larger than expected. PVSyst’s module layout feature has a concept for assigning the PV modules defined in the system to the tables defined in the 3D scene. According to PVSyst’s documentation, before entering the module layout, the system and the 3D scene must be properly defined, and the number of modules must correspond for each orientation.

In other words, module settings, string configuration, 3D layout, and shading assessment may appear to be separate tasks, but in reality they are connected. To perform reliable simulations in PVSyst, it is important to verify the settings of individual modules and then check that there are no inconsistencies in the system's overall connection conditions.

Common mistakes and verification process for module configuration

Common mistakes in PVSyst module configuration include selecting the wrong model number, inconsistencies with the datasheet, overlooking temperature coefficients, misidentifying cell configuration, neglecting module quality losses, insufficient justification for mismatch losses, and inadequate verification of string voltage. Each of these may seem like a small error individually, but they affect energy yield, loss diagrams, design comparisons, and project viability assessments.

First, choosing the wrong model number is the most common problem. Because many modules are registered in PVSyst’s database, you can end up selecting a similar model number when searching. Even if the series name is the same, output class, number of cells, dimensions, and current values can differ. In particular, when a manufacturer updates a product line over a short period, old and new specifications tend to coexist. As a countermeasure, it is important not to rely only on the model name in PVSyst, but to cross-check the model number and key figures against the manufacturer’s datasheet.

Next, discrepancies with the specification sheet. If any of Pmax, Vmpp, Impp, Voc, or Isc differ, they will affect string design and power generation. When checking the values in the specification sheet, verify whether they are STC values or NMOT values, what the measurement conditions are, and whether the units match. Because the specification sheet may list values for multiple conditions, accidentally referencing values from a different condition can cause the model’s assumptions to become misaligned.

Overlooking temperature coefficients is also important. Failing to verify Voc at low temperatures can lead to a design that exceeds the inverter's maximum input voltage during cold conditions. If Vmpp at high temperatures is not checked, you may overlook incompatibility with the MPPT range. Because temperature conditions vary by region, the number of modules per string that posed no problem in typical projects may not be suitable in cold climates or high-temperature regions.

Misidentification of cell configuration and bypass diodes is a common issue in shading assessment. When there are roof chimneys, parapets, antennas, surrounding buildings, front-row ground-mounted shadows, fence shadows, etc., it is necessary to consider the relationship between how shadows fall and the internal structure of the module. For a detailed shading evaluation in PVSyst, it is essential to be mindful of module portrait/landscape orientation, cell layout, and substring configuration.

Module quality losses and mismatch losses tend to be left at their initial values. Using initial values is not inherently wrong, but you need to verify whether they match the project's objectives. At the estimation stage, the detailed design stage, for submissions to financial institutions, and for performance comparisons, the required level of conservativeness and the granularity of supporting evidence differ. Not only the magnitude of the loss values but also whether you can explain the rationale for their settings is important.

The verification workflow is: first prepare the datasheet for the module to be adopted and cross-check it with the PAN file selected in PVSyst. Next, verify the power output, voltage, current, temperature coefficients, dimensions, cell configuration, and output tolerance. Then proceed to the system definition and check the number of modules per string, number of parallel strings, MPPT allocation, inverter input range, and DC/AC ratio. Furthermore, under detailed losses check module quality, mismatch, IAM, temperature losses, and wiring losses, and if there are shadows, verify consistency with the 3D scene and module layout.

By following this flow, module configuration in PVSyst becomes not merely a data-entry task but a verification process that enhances design quality. Especially for beginners, it is important not to take the values displayed on the screen at face value, but to proceed while asking, "Where in the specification does this number correspond?", "What does this loss mean?", and "Does this string configuration meet the temperature conditions?"

Summary

The basics of module configuration learned from the PVSyst manual do not stop at selecting a module. You must understand the roles of the database and PAN file, verify manufacturer specifications and STC conditions, check size, cell configuration, and bypass diodes, interpret temperature coefficients and low-light characteristics, assess module quality, mismatch, and IAM losses, and finally confirm the impact on string configuration and inverter selection.

PVSyst is a useful software that automatically assists with many items, but if you proceed without understanding the meaning of the settings, the basis for the energy yield simulation becomes weak. In particular, module settings form the basis for energy yield, loss diagrams, PR, inverter selection, shading assessment, and economic evaluation, so it is important to check them carefully in the early stages.

In practice, review the registered data in PVSyst together with the manufacturer’s datasheet, the project’s installation conditions, the inverter specifications, and the loss settings as a whole. Even just checking that the model number matches, the STC values are consistent, there are no contradictions in the temperature coefficients, the cell configuration and dimensions are correct, and that you can explain the basis for the loss settings will greatly improve the reliability of the simulation.

The purpose of reading the PVSyst manual is not just to learn how to operate the interface. It is to understand why each item is necessary, which settings affect energy yield, and where to check to prevent design mistakes. If you grasp the six basic module settings, whether you are using PVSyst for the first time or reviewing an existing project, it will be easier to produce more convincing energy yield simulations.