7 Basic System Design Items Learned from the PVSyst Manual

Table of Contents

• Why Learn System Design from the PVSyst Manual

• Basic Item 1: Decide the project conditions and design objectives first

• Basic Item 2: Correctly set the location information and meteorological data

• Basic item 3: Organize the azimuth, tilt angle, and installation method

• Basic Item 4: Verify the combination of modules and inverters

• Basic Item 5: Evaluate the impact of shadows step by step

• Basic item 6: Adjust loss settings to better reflect real-world conditions

• Basic Item 7: Review the design by comparing simulation results

• Common stumbling points for beginners when reading the PVSyst manual

• Practical approach to avoid failures in system design

• Summary

Why Learn System Design from the PVSyst Manual

The purpose of reading the PVSyst manual is not simply to learn how to operate the interface. In designing a solar power generation system, many conditions affect energy production: the installation site, meteorological data, modules, inverters, azimuth, tilt angle, shading, various losses, output limitations, and so on. By using PVSyst, you can organize these conditions into a single project and, while comparing multiple design proposals, check the annual energy production and the breakdown of losses.

The official documentation describes PVsyst 8.1 as PC software for the study, sizing, and data analysis of entire photovoltaic systems, stating that it can handle systems such as grid-connected, standalone (off‑grid), pumping, and DC‑grid systems. In addition, because it also provides meteorological data, equipment databases, and general solar-energy-related tools, it is positioned for wide use by designers, engineers, researchers, and for educational purposes.

Therefore, many people who search for "PVSyst manual" are not just trying to find where the initial settings are located; they also want to know the order in which to enter conditions, which numerical values to prioritize, and which parts of the result report to consult for making design decisions. In particular, in system design the assumptions entered at the start have a large impact on subsequent results. Rather than deciding the design based solely on module capacity or inverter capacity, it is important to build up conditions step by step within PVSyst and adjust them while reviewing the results.

PVSystのProject designは、詳細なシミュレーションを使って太陽光発電システムの設計と性能分析を行う領域であり、プロジェクトには地理的条件や気象データが含まれ、複数のシミュレーション実行を「variant」として比較できる構造になっています。 この考え方を理解しておくと、マニュアルの各項目が単独の操作説明ではなく、設計検討の流れの中でつながっていることが見えてきます。

Basic Item 1: Decide the project conditions and design objectives first

Before starting system design in PVSyst, the most important thing is to clarify the project conditions and the design objectives. For example, even for the same photovoltaic installation, the numbers to look at and the design options to compare differ between a ground-mounted project whose main purpose is selling electricity, a rooftop project that prioritizes self-consumption, and a project that assumes battery storage or output control. Even if you proceed while reading the PVSyst manual, if you don't decide upfront "what the simulation is meant to determine," the conclusions will become unclear when you look at the result report.

At the starting point of system design, organize the equipment capacity, available installation area, grid interconnection conditions, assumed operation period, design constraints, surrounding environment, and so on. In PVSyst you can manage multiple proposals using projects and variants, but if the real design conditions remain unclear, what you think is a comparison may simply end up as a check of input differences. For example, when comparing a plan to increase the number of panels with a plan to change inverter capacity, you need to clarify whether the purpose of the comparison is to maximize energy production, to verify the appropriateness of the oversizing ratio, or to judge the acceptability of peak-cut losses.

The official documentation's Project design procedure shows that you should first define the project via Project/Variant; for each project, specify the geographic location, meteorological data, and, when necessary, albedo data; and for each variant define the orientation and system conditions. In other words, PVSyst is not "software for just producing an energy estimate," but is fundamentally meant to be used as a design-study tool to organize assumptions and compare multiple variants.

What beginners often stumble over is diving into detailed loss rates and intricate shadow settings from the outset. Of course, detailed settings are important, but if you adjust only the details while the design objectives remain unclear, it becomes difficult to interpret the results. First solidify the project's basic conditions, review the overall picture with rough variants, and then work out the detailed conditions—this sequence is realistic.

Basic Item 2: Correctly Set Location Information and Weather Data

In solar PV simulations, the configuration of site information and meteorological data forms the foundation of the results. Because power output is influenced by solar irradiance, temperature, solar altitude, seasonal variations, and weather trends, even if modules and inverters are correctly selected, the overall reliability of the results will decrease if the meteorological data deviate from reality. When reading the PVSyst manual, you should be aware not only of how meteorological data are loaded but also which location those data represent and how close that location is to the design site.

In PVSyst projects, geographic conditions and meteorological data are treated as basic information. The official documentation also states that Project design retains the geographic context and meteorological data within the project's framework and treats different simulation runs as variants. This indicates that meteorological data are not merely auxiliary settings but are fundamental premises of the system design itself.

In practice, multiple candidate data sources may be available, such as data from nearby observation stations, satellite-derived data, and measured data held by the designer. What is important is not to judge solely by the amount of solar radiation. Average temperature, monthly solar radiation patterns, whether the site is in a snowy area, whether it is coastal or mountainous, and morning/evening solar conditions caused by surrounding topography also affect power generation. Especially for rooftop installations and projects in mountainous areas, a slight change in location can greatly alter shading and solar conditions.

Albedo settings are another easy-to-overlook point. Since albedo involves the component reflected from the ground surface, its impact differs for snow, sand, grass, pavement, and so on. In routine designs there is no need to over-refine it, but for bifacial modules, snowy regions, or large ground-mounted projects it is worth verifying the appropriateness of the settings.

When learning how to set up meteorological data using the PVSyst manual, it's important not only to learn how to operate the input screens but also to be aware of how those settings will affect the results. For the initial simulation, check the overall trends using standard data, then review the data sources and site conditions and compare the differences so the results are easier to use for design decisions.

Basic Item 3: Organize Azimuth, Tilt Angle, and Installation Method

As basic elements of system design, defining azimuth, tilt angle, and mounting method is indispensable. In PVSyst, specifying the orientation and angle of the mounting surface changes the incident irradiance on the receiving surface and the seasonal generation trends. Although a south-facing orientation is often considered standard in Japan, in actual projects constraints such as roof shape, site shape, racking layout, neighboring property boundaries, maintenance access, snow accumulation, and wind loads can make it impossible to choose the ideal azimuth or tilt angle.

In PVSyst's Project design procedure, after defining the project, the flow shows setting the plane orientation for each variant, and then defining the System properties. This order is also natural in practical work, because unless the conditions of the mounting surface are decided first, it is difficult to proceed with considerations such as the number of modules, string configuration, inverter capacity, shadow assessment, and loss settings.

When considering azimuth and tilt angles, you should not only look at annual power generation but also check monthly generation trends. Lowering the tilt angle makes the system more exposed to summer solar radiation, but it can affect soiling, snow accumulation, drainage, and racking conditions. Increasing the tilt angle can be advantageous for winter generation and snow shedding, but it may require wider row spacing and could reduce the installed capacity per site.

On roof installations, the orientation and tilt can differ for each roof surface. If panels are installed not only on the south face but also on the east and west faces, peak generation periods are spread out, which affects compatibility with inverters and self-consumption. For ground-mounted installations, considerations for mutual shading and series/parallel configurations also change depending on the mounting system, such as fixed racks, tracking mounts, east-west racks, or shed layouts.

When reading the PVSyst manual, it is important not to remember azimuth and tilt angles as mere input values, but to treat them as primary variables for comparing design options. For example, comparing an option that changes the tilt angle for the same installed capacity, an option that changes row spacing on the same site, and a south-facing option versus an east-west option reveals differences in energy production, shading losses, peak output, and constructability.

Basic Item 4: Verify the combination of modules and inverters

In PVSyst system design, the combination of modules and inverters is a central consideration. The number of modules, number of series strings, number of parallel strings, inverter capacity, number of MPPT inputs, voltage range, and overloading ratio all affect energy production and losses. Rather than simply assuming that “increasing module capacity will increase energy production,” it is necessary to verify that the inverter’s input conditions and operating range are being met.

In PVSyst, you can evaluate the series and parallel configuration of modules for a selected inverter model. The official documentation explains that, within Project design, support is provided to design the PV array — that is, to determine the number of series and parallel modules — according to the chosen inverter model and related factors. By using this feature, designers can assemble a realistic configuration while checking voltage conditions and capacity ratios.

What is particularly important is the ratio between inverter capacity and array capacity. In PVSyst’s inverter/array sizing, the PNom ratio is based on allowable overload losses during operation, and it presents an approach that takes into account the annual energy balance under real-world conditions such as meteorological data, orientation, and losses. Furthermore, detailed simulations are considered the benchmark for accurately assessing overload losses.

This means you should not judge an oversizing ratio solely by a simple capacity ratio. Even with the same oversizing ratio, actual peak clipping losses vary depending on regional solar irradiance conditions, module orientation, tilt angle, temperature conditions, shading, and whether output limitations are present. For example, in east-west oriented systems the peak output is spread out, so the approach to inverter sizing may differ from that for south-facing fixed-tilt systems.

Also, attention is required to the open-circuit voltage at low temperatures, the operating voltage at high temperatures, the MPPT range, and differences in the number of modules per string. Just because PVSyst does not show warnings does not necessarily mean that construction and maintenance aspects have been fully verified. When learning the electrical design screens in the PVSyst manual, it is important to perform consistency checks in the software together with verification of the actual equipment datasheets and installation conditions.

Basic Item 5: Evaluate the Impact of Shadows in Stages

In the design of photovoltaic systems, shading assessment is a factor that has a large impact on energy production. Shading includes horizon-direction shadows from distant terrain, nearby shadows from adjacent buildings and trees, parapets, utility poles, and mutual shading between rows of racking. When reading the PVSyst manual, rather than trying to understand all of the shading settings screens at once, it is easier to organize your understanding by separating them into stages: distant shading, near-field shading, and electrical shading losses.

The official documentation explains that nearby shading refers to shadows cast by nearby objects that are visible on a solar photovoltaic field, and that the Shading Factor is defined as the ratio of the shaded area to the total sensitive area. It also states that handling nearby shading is more complex than distant shading and requires a detailed 3D description of the PV system and its surrounding environment.

As this explanation shows, shading analysis is one of the more difficult areas in PVSyst. If a beginner tries to build a detailed 3D scene right away, they can spend too much time on geometry input and lose sight of the purpose of the design decisions. A realistic workflow is to first assess how much of a problem shading is using site photos, drawings, surrounding building heights, and checking the sun path, and then reproduce it in PVSyst to the level of accuracy required.

Also, shading losses are not only those caused by solar radiation being simply blocked, but also losses caused by electrical mismatch that occurs when some modules within a string are shaded. In the official documentation, for the beam component of nearby shading, they distinguish between an illumination loss corresponding to the shortfall of irradiance on the cells and an electrical loss caused by mismatch in the electrical response of series-connected modules or parallel strings.

In design practice, the greater the impact of shading on a project, the more carefully module layout, string allocation, MPPT grouping, spacing between racking rows, and distances to surrounding obstructions must be considered. In particular, shadows from roof parapets, equipment, chimneys, railings, and adjacent buildings affect not only annual energy yield but also generation by time of day in the morning and afternoon. When evaluating shading in PVSyst, it is important to check not only the annual loss rate but also in which seasons and at what times of day shading occurs.

Basic Item 6: Bring loss settings closer to real-world conditions

Loss settings cannot be avoided when learning system design from the PVSyst manual. In photovoltaic systems, power output is reduced by various factors such as module temperature, incidence angle characteristics, soiling, wiring resistance, mismatch, degradation over time, equipment downtime, auxiliary consumption, and transformer losses. To bring simulation results closer to reality, these losses need to be adjusted to match the project conditions.

The official documentation notes that PVSyst’s array loss parameters are set to reasonable default values initially, so adjustments can be made in the second stage of the system study. It also recommends that, after the first simulation, each loss factor be carefully defined to match the PV system. This approach is especially important for beginners. Rather than trying to enter all loss values perfectly from the outset, it is easier to first produce results under standard conditions and then adjust while checking the differences.

The losses handled by PVSyst include IAM losses, soiling losses, losses related to low irradiance, thermal losses, LID, module quality, mismatch, degradation, optimizer losses, DC wiring losses, AC wiring losses, external transformer losses, auxiliary consumption, system downtime losses, and others. In the official documentation, these types of losses are also categorized as array or system losses.

In practice, what you should particularly check is whether the loss settings are too optimistic. For example, if you set soiling losses too low you may overlook the effects of sand and dust, pollen, bird damage, soiling after snowfall, and cleaning frequency. Regarding temperature losses as well, they can be more severe than standard conditions for rooftop installations with poor ventilation or in high-temperature regions. Wiring losses are related to cable length and cross-sectional area and the planned arrangement of combiner boxes and PCS, so they need to be reviewed as the electrical design progresses.

On the other hand, setting losses overly conservatively can cause a design proposal to be evaluated more negatively than necessary. The loss settings in PVSyst are not intended to hide project risks or to generate pessimistic figures. It is important to set them as explainable assumptions based on site conditions, equipment specifications, construction plans, and operation and maintenance policies. Ultimately, you must be able to explain to stakeholders which losses were set at what percentages and the rationale behind those choices.

Basic Item 7: Compare simulation results and review the design

The purpose of performing system design with PVSyst is not to produce results and stop. It is important to interpret the simulation results, review the design proposal, and, when necessary, create and compare variants. The results report contains information useful for design decisions, such as annual energy production, monthly energy production, Performance Ratio, loss diagram, inverter losses, wiring losses, and shading losses.

The official documentation explains that once the required parameters are defined and no error messages are shown, a simulation can be started and you can use the normal Run Simulation or Advanced simulation. It also states that if the weather data are subhourly, subhourly time steps can be selected, but for iterative design hourly simulations are faster, and the recommended approach is to use more detailed time steps once the design is close to its final stage.

This workflow is effective in practice as well. In the initial stage, quickly compare azimuth, tilt angle, capacity ratio, and differences in major losses to determine the design direction. In the final stage, check for shading, detailed losses, output limits, monthly trends, and any abnormal loss items, and organize them into a form that can be explained in a report. Rather than aiming for final precision from the outset, progressing from coarse assessments to detailed analyses is the key to using PVSyst efficiently.

When interpreting results, it is important to look not only at annual energy production but also at the breakdown of losses. In the simulation variables listed in the official documentation, variables such as array behavior, inverter behavior, energy output, and efficiency indicators are organized, and the Performance Ratio is shown as the relationship between final system energy production and the incident solar irradiance energy on the receiving surface. In other words, when looking at PVSyst results, you need to track not simply whether the kWh is large or small, but at which stages and how much loss occurs.

For example, if the power generation is lower than expected, the cause might be the solar irradiance data or the tilt angle. Shading losses, temperature losses, inverter overload losses, wiring losses, output curtailment, and downtime losses may also be affecting the result. By examining a loss diagram to see where energy is being reduced most significantly, you can identify the design points that should be improved.

Common Pitfalls for Beginners When Reading the PVSyst Manual

What trips up people reading the PVSyst manual for the first time is the large number of screen items. While PVSyst allows detailed handling of photovoltaic systems, it has many settings screens and technical terms, and trying to understand everything at once can be overwhelming. In particular, if you proceed without understanding the relationships among items such as Project, Variant, Orientation, System, Losses, Near Shadings, Module Layout, Simulation, and Results, it becomes difficult to judge which changes will affect the results.

Beginners should first grasp the overall flow of a project. The official documentation's procedure shows the flow: select the system type in Project Design, define Project/Variant, configure for each variant the orientation, system conditions, losses, shading, module layout, etc., check warnings and run the simulation, then save and compare the results. If you memorize this sequence as the basic workflow for design tasks, reading the manual becomes considerably easier.

It is also important to correctly understand PVSyst’s warning indications. The official documentation explains that the program checks parameter consistency and issues an orange warning when a simulation is possible but caution is required, and a red warning when there is a problem that prevents simulation. Red warnings should always be resolved, but orange warnings should not be ignored either. It is safer to treat them as conditions that may be acceptable from a design standpoint but whose justification should be verified.

Another stumbling block is overconfidence in default values. PVSyst provides initial values, but that does not mean they are optimal for every project. In particular, loss settings, soiling, temperature, wiring, downtime rate, shading, and output limits all vary depending on the project. Using default values for the first simulation is a good approach, but as you approach the final report stage you should always review the validity of the input values.

The PVSyst manual is most effective when read not just to follow procedural steps but to understand the rationale behind design decisions. For example, rather than focusing on “which button to press,” reading while considering “why this setting affects energy yield,” “whether this loss matches local conditions,” and “what you want to conclude from this variant comparison” will transform the information into knowledge you can use in practice.

Practical Approach to Avoid Failures in System Design

To avoid failures in system design using PVSyst, it is important not to create a perfect model from the outset but to improve accuracy incrementally. First, set the project purpose, installation location, system type, estimated capacity, azimuth, tilt angle, and main equipment, and run the initial simulation. Then review the results to check the scale of energy production, monthly trends, major losses, and any warnings.

Next, we will examine each important design issue one by one. For example, increasing the number of modules increases power generation, but by how much do inverter overload losses increase? Changing the tilt angle affects not only annual generation but also the balance of output between winter and summer—how does it change? Widening the row spacing reduces shading losses, but by how much does the installed capacity decrease? In this way, rather than trying to judge everything with a single variant, separating variants according to the purpose of comparison clarifies design decisions.

In PVSyst, it is important to save variants after a simulation so they can be compared later. The official documentation also recommends saving each variant after a simulation, using Save as to avoid overwriting, and giving descriptive names that are easy to identify in the final report. In practice, including words in the variant name that indicate what changed—such as "tilt 10 degrees", "east-west layout", "PCS capacity change", or "detailed shading reflected"—makes later comparisons easier.

Also, before reviewing the final report, it is important to make a habit of checking the consistency of the input conditions. Verify whether the module model is correct, whether the number of inverters and the number of inputs match the actual design, whether the string configuration is feasible, whether the meteorological data are representative of the site, whether the shading settings reflect on-site conditions, and whether the loss rates have a sound basis. Even if the results look plausible, if the input assumptions are wrong you may make incorrect design decisions.

PVSyst can produce detailed results, which can lead to the numbers in reports being taken out of context. Energy generation forecasts are simulations based on the configured conditions, and actual generation is affected by weather, maintenance, equipment condition, outages, soiling, grid constraints, and other factors. For that reason, it is important not only to learn how to operate PVSyst from the manual but also to be able to explain the assumptions, the conditions used for comparison, and the design intent.

Summary

When learning system design from the PVSyst manual, simply memorizing the sequence of on‑screen operations is not enough. First, clarify the project conditions and design objectives, prepare the site information and meteorological data, decide the azimuth, tilt angle, and mounting method, and verify the combination of modules and inverters. On top of that, it is important to evaluate shading impacts step by step, adjust the loss settings to better reflect real conditions, and review the design while comparing simulation results.

The strength of PVSyst is that it allows you to create multiple variants and review the differences between design proposals as energy production and loss breakdowns. If you understand the Project design concept, PVSyst can be used not merely as power-output calculation software but as a practical analysis tool to support design decisions.

For beginners, rather than trying to perfect all settings from the start, it is recommended to first run simulations under standard conditions and then adjust important items one by one while reviewing the results. Check warning messages, loss diagrams, monthly energy production, Performance Ratio, inverter losses, shading losses, and so on, and being able to explain why those results occurred is the first step to mastering PVSyst in practical work.

In the final system design, it is necessary to verify not only the numerical values in PVSyst but also site conditions, equipment specifications, constructability, operation and maintenance, grid interconnection conditions, and consistency with the business plan. By reading the PVSyst manual along the design flow and understanding what each setting means for the results, you can improve not only the accuracy of the power generation simulation but also the quality of design documentation that is easy to explain to stakeholders.