5 Items to Avoid Failure When Creating a Project in the PVSyst Manual

Table of Contents

• Prerequisites You Should Decide Before Reading the PVSyst Manual

• Objectives and project conditions to confirm first when creating a project

• How to Read Meteorological Data and Installation Locations to Avoid Confusion

• Capacities and equipment conditions that commonly cause errors in system design inputs

• Why Results Change Based on Shadow, Orientation, and Tilt Settings

• How to Proceed with Project Creation, Including Report Review

• Key points for effectively using the PVSyst manual in practice

• Summary

Assumptions You Should Decide Before Reading the PVSyst Manual

Many people consulting the PVSyst manual want to proceed with PV power generation output simulations but are unsure which screen to use to set which parameters, or which input items will greatly affect the results. Especially when creating a project for the first time, you may be able to fill in the fields on each screen in order, but it becomes difficult to judge whether those settings match the project conditions or whether you have made assumptions that will be hard to revise later.

PVSyst is not a tool that simply outputs energy production by entering the number of solar panels and inverter capacity. It is a simulation environment for combining many conditions—installation location, weather data, azimuth, tilt angle, surrounding shading, wiring losses, temperature conditions, and module and inverter combinations—to check annual energy production and the breakdown of losses. Therefore, if you proceed in the early stages of project creation without sufficiently organizing the conditions, it becomes difficult to judge whether the generation and loss rates shown later are reasonable.

What matters here is not reading the manual from start to finish, but understanding the workflow necessary to create a project, clarifying the items you need to check for your own case, and only then proceeding with the operations. The manual contains many functional descriptions, but what is initially required in practice is to correctly launch the project, avoid major deviations in installation conditions, align the system configuration with the actual plan, and ensure you are able to review the result report.

This article organizes five key items to check, following the practical workflow, to ensure you don't fail when creating projects with the PVSyst manual. It explains in order the points that are easy to get confused during initial setup, how input mistakes affect results, and the assumptions you should verify before reviewing reports. Even if many items look technical, by grasping the meaning of each one step by step, operating PVSyst becomes easier to understand not as mere data entry but as a procedure for validating design conditions.

Objectives and Project Conditions to Confirm First When Creating a Project

When creating a project in PVSyst, the first thing you should confirm is the purpose of the simulation. Even for the same solar power project, the required input precision and the items you need to check will differ depending on whether you use it for a preliminary estimate, a design comparison, or as explanatory material for financial institutions or the client. If you proceed without deciding the purpose, you may spend too much time on minor details or, conversely, look only at the results while leaving important assumptions vague.

For example, in an early-stage site screening it is important to first check the installation location, weather data, expected capacity, azimuth, tilt, and estimated losses, and make sure you are able to compare multiple options. On the other hand, at a stage closer to detailed design you need to input more specific information such as the modules and inverters to be used, string configuration, wiring distances, shading effects, and temperature losses. When reading the PVSyst manual, being aware of which stage of study you are in will make it easier to separate the items that are necessary from those that can be deferred.

When creating a project, it is important not only to enter the project name and installation location but also to clarify the scope of what will be examined. Whether it is a rooftop installation, a ground-mounted installation, an agricultural (agrivoltaic) system, a self-consumption system, or based on grid interconnection, the perspective for evaluating generation output will change. For rooftop installations, orientation and tilt are often constrained by the building’s shape; for ground-mounted installations, racking layout, row spacing, surrounding terrain, and shading considerations become important. For self-consumption systems, in addition to generation output itself, it is also necessary to consider the relationship with demand and how to view peak periods.

Also, at the project creation stage, it is important to be mindful of leaving a record of the rationale behind the input values. The values entered on the PVSyst screen can be checked later in the report, but it will not automatically explain why those values were adopted. For example, reasons for setting the tilt angle to 20 degrees, for choosing an azimuth slightly east of true south rather than due south, or for estimating the level of wiring losses should be organized by the design team. Even when operating while reading the manual, rather than simply entering what appear to be recommended values, it's important to set parameters that can be justified against the project's conditions.

A common point of failure is reusing existing samples or past projects and proceeding after only changing the project name. If the previous settings also apply to the current project, there is no problem, but if the installation area, module specifications, inverter configuration, shading conditions, or loss conditions differ, the results can change significantly. In particular, if the meteorological data or installation location remain as in the past project, the simulation may appear to be complete while in reality it is calculating energy production under the conditions of a different region.

When reviewing project setup in the PVSyst manual, it's helpful to distinguish between assumptions you will lock in and those you'll compare later. Treat the installation location and intended use as fixed basic conditions, while making capacity, tilt angle, module type, inverter configuration, and so on subjects for comparison. Making this distinction also clarifies what has been changed when you create variations.

How to Read Weather Data and Avoid Mistaking the Installation Location

When performing energy yield simulations in PVSyst, the weather data and the site settings are extremely important. The annual energy output of a solar power system is strongly influenced by irradiance, temperature, solar altitude, and surrounding conditions. Therefore, if the installation location is not set correctly or if meteorological data that are far from the actual project site are used, no matter how finely equipment settings are adjusted later, the overall reliability of the results will be reduced.

When viewing the meteorological data entries in the PVSyst manual, you should first understand that specifying the site and selecting the meteorological dataset have different meanings. Site specification—latitude, longitude, elevation, time zone, etc.—defines the assumptions used for solar position calculations and local conditions. Meteorological data, on the other hand, are the measurements, such as solar radiation and temperature taken near that site, used in the simulation. Selecting a nearby point on the map does not necessarily mean the meteorological dataset is the best choice for the actual project.

When entering the installation location, check whether the latitude and longitude are close to the project site, whether the elevation does not deviate significantly, and whether the area's meteorological characteristics are reflected. In mountainous, coastal, snowy, or high-temperature regions, trends in solar radiation and temperature can vary even within the same prefecture. Especially for large projects or when using the data for project feasibility assessments, it is important not only to use the nearest meteorological data as-is but also to understand how it differs from the local site conditions.

A common pitfall with meteorological data is selecting data without being aware of differences in data types and time periods. Whether you use average-year data, data from a specific year, or data imported from external sources changes the meaning of the results. Average-year data is suitable for grasping typical power generation, but it will not exactly match the generation in any particular year. Specific-year data can be useful for validating past years, but caution is needed when treating it as a standard outlook for the future.

When selecting meteorological data, you should check not only solar irradiance but also temperature. Because PV modules' output decreases at high temperatures, temperature conditions affect temperature-related losses. In hot regions, even with high solar irradiance, temperature-related losses may increase, and in cold regions you need to separately consider snow cover and operating conditions at low temperatures. If PVSyst results show energy production that is higher or lower than expected, it is important to go back and verify the meteorological data assumptions, not just the module or inverter settings.

When checking the installation site and meteorological data, it is important not to stop at simply viewing the screen display at the time the project is created. You should be able to explain later, when reviewing the report, which location’s data were used and under what weather conditions the calculations were performed. The power generation figures are the results of the assumptions you entered. If those assumptions remain unclear, you cannot judge whether the results are good or bad.

When comparing multiple candidate sites, you need to decide in advance whether to standardize the meteorological data conditions or to use the data that is best for each location. If you standardize conditions too much, local differences become hard to see, and if you use different data for each site, the assumptions for comparison become more complex. When using the results as comparative material, organizing the rationale behind your data selection will make it easier to explain.

Capacities and equipment conditions that are easy to get wrong in system design inputs

When creating a project in PVSyst, after the meteorological data and the site location, entering the system design is a major point. Here you configure the solar modules, inverters, string configuration, installed capacity, connection conditions, and so on. For generation simulations, it is not sufficient to simply enter the panel capacity; you must verify whether the module-inverter combination is realistic and whether the voltage range and the approach to oversizing are appropriate.

The first thing to clarify is the difference between DC capacity and AC capacity. DC capacity refers to the capacity on the photovoltaic module side, while AC capacity is considered the capacity on the inverter output side. In practice, there are designs in which module capacity exceeds inverter capacity, but in that case it is necessary to understand the effects on energy production and peak clipping. When looking at the system design section of the PVSyst manual, it is important not to confuse which capacity corresponds to which side.

A common cause of failures in equipment specifications is selecting the wrong specifications for the modules or inverters to be used. Even if model numbers look similar, output, voltage, temperature coefficient, maximum input voltage, MPPT range, and so on may differ. Just because a similar model exists in the database does not mean it is identical to the equipment that will actually be used. While approximate values may be used in early studies, as the project moves closer to detailed design it is necessary to confirm that the specifications match those of the equipment planned for use.

In string configuration, the number of modules in series per string, the number of parallel strings, and the allocation of inverter inputs are important. If the number of modules in series is too low, voltage conditions can be unfavorable under low irradiance or high temperatures; if it is too high, the maximum voltage may be exceeded at low temperatures. When warnings or inconsistencies appear in PVSyst, it is important not to change the numbers simply to clear the warnings, but to understand why that condition is problematic.

Also, when entering the number of inverters and their input configuration, confirm that they are consistent with the actual switchboard/panel configuration and construction plan. Even if they work in simulation, if they do not align with on-site cable routes, junction boxes, racking layout, maintenance space, and grid interconnection requirements, they are inadequate as a practical design. PVSyst is useful for evaluating energy production and losses, but it does not automatically guarantee constructability or maintainability.

When setting capacity, attention must also be paid to how oversizing is handled. While oversizing can increase power generation during low-irradiance periods and in the mornings and evenings, it can cause peak clipping during periods of strong irradiation due to the inverter's output limit. In PVSyst results, these effects are reflected in losses and energy yield, but if you look only at annual energy production without understanding what this means, you may make incorrect design decisions. If oversizing is adopted, decisions must be made based on annual energy production, peak clipping, equipment cost, and grid connection conditions.

Variation management is also important when entering system design data. PVSyst allows you to create and compare multiple cases, but if the differences between cases are ambiguous, you won't be able to tell later which setting change produced a given result. If you mix cases that change module capacity, cases that change inverter capacity, cases that change tilt angle, and cases that change loss conditions, it becomes difficult to understand the meaning of the comparisons. When creating a project, clarify the axes of comparison and make the case names reflect the differences so they are easier to handle in practice.

Why the results change depending on shadow, azimuth, and tilt settings

When evaluating energy production in PVSyst, azimuth and tilt angles are fundamental parameters that greatly influence the results. The direction the solar modules face and the angle at which they are installed change the amount of incident solar radiation they receive. For roof-mounted installations, the building's roof pitch and orientation often constrain those angles, whereas for ground-mounted systems the tilt must be chosen considering energy production, constructability, wind load, row spacing, and maintenance.

When checking the azimuth and tilt fields in the PVSyst manual, always confirm the reference used for the angles you enter. Misunderstanding the azimuth reference can reverse east and west or cause you to set a direction different from true south. For tilt angles, you also need to confirm whether the angle is measured from the horizontal plane or is a value converted from the roof pitch. It may be simple to just enter numbers into the input fields, but if you get the angle reference wrong the simulation results can change significantly.

Shadow settings also have a significant impact on power generation. Shadows from surrounding buildings, trees, mountains, rooftop equipment, and between rows of mounting structures can reduce power output depending on the time of day and season. Because shadows lengthen when the solar altitude is low, they are particularly likely to affect generation in the mornings and evenings and during winter. PVSyst has a function to evaluate the impact of shading, but if shading is not configured, losses from surrounding obstacles will, of course, be less likely to be reflected.

A common mistake when configuring shadows is underestimating them. If there are clearly shadows from surrounding buildings or trees on site but the simulation is run without shadows, the estimated energy production can be overstated. Conversely, if the actual impact of shadows is limited but overly strict shadow conditions are applied, the estimated energy production can be understated. The important thing is not just whether shadows are included or not, but whether the modeling is reasonable for the on-site conditions.

For ground-mounted projects, it is also necessary to verify the relationship between row spacing and tilt angle. Increasing the tilt angle can be advantageous for winter solar gain, but it can also cause row-to-row shading to extend. Widening the row spacing can reduce the impact of shading, but it may decrease the capacity that can be installed on the same site. Thus, it is necessary to consider not only energy generation but also the balance with land-use efficiency and construction costs. PVSyst simulation results can be used as input for such design decisions.

In rooftop installation projects, the orientation and tilt can differ for each roof surface. When installing not only on the south-facing surface but also on east- and west-facing surfaces, the timing of generation peaks changes. While south-facing systems tend to secure annual generation more easily, east- and west-facing systems have more dispersed generation times and can sometimes be a better match for self-consumption. When handling multiple surfaces in PVSyst, it is important to correctly separate and enter the conditions for each surface.

Settings for shading, azimuth, and tilt are important not only for the power output figures but also for understanding the breakdown of losses. If the results report shows large shading losses, you need to review the shading model, row spacing, surrounding obstructions, and installation angle. When power generation is lower than expected, checking whether layout, angle, or shading conditions are the cause—rather than immediately increasing module capacity—is fundamental to avoiding failures in project design.

How to Proceed with Project Creation Including Report Review

The purpose of creating a project in PVSyst is not simply to complete the inputs, but to verify the results and make them usable for design decisions. Therefore, the project creation workflow should be considered as a continuous sequence of tasks: initial settings, meteorological data, system design, shading conditions, loss conditions, running the simulation, and reviewing the reports. Even if the intermediate inputs are correct, if you cannot interpret the result reports, it will be difficult to apply the work in practice.

The first thing to check in a report is the project's assumptions. Confirm that the site, weather data, modules, inverters, capacity, azimuth, tilt, and loss conditions are set exactly as you intended. Before looking at the energy production numbers, it is important to first verify that the assumptions are correct. If there is an error in the assumptions, no matter how favorable the production figures look, the results become difficult to use as a basis for decision-making.

The next thing to check is the balance between annual generation and monthly generation. If you only look at the annual value, seasonal biases and drops in specific months can be hard to see. If generation falls sharply in winter, check the effects of solar irradiance, shading, snow cover, and tilt angle. If summer generation does not reach expectations, you need to check temperature-related losses from high temperatures and inverter limitations. Viewing monthly trends makes it easier to understand generation characteristics rather than just the total amount.

Checking the loss diagram is also important. In PVSyst's report, the losses from solar irradiance to the final output are shown step-by-step. By looking at this, you can identify at which stage and how much loss is occurring. Shading losses, temperature losses, wiring losses, mismatch losses, inverter losses, and so on can provide clues for design improvements. Rather than looking at the loss-rate numbers in isolation, it is important to judge whether they are excessively large for the project conditions and whether they are items that can be improved.

A common mistake when reviewing reports is judging performance solely by the annual energy production. Even if the annual production is high, it will naturally be higher if the entered capacity is oversized. Conversely, even if the annual production appears low, it may be reasonable when considering the site’s solar irradiation conditions, roof orientation, and shading. When evaluating energy production, you need to look at production per installed capacity, the breakdown of losses, monthly trends, and consistency with the design conditions.

When comparing multiple proposals, it is important to align the report’s baseline assumptions. If one proposal includes shading while another does not, or one uses different meteorological data and another uses different loss assumptions, simply comparing only the energy production becomes of limited value. If what you want to compare is the difference in tilt angle, you need to keep all other conditions the same as much as possible. If you want to compare different modules, you must also consider differences in installed capacity and inverter configuration.

In practice, PVSyst reports are sometimes used for internal reviews and for explaining results to clients. In such cases, it is important not only to present the numbers in the report but also to be able to explain under which conditions those results were calculated. If you organize the assumptions when creating the project and clarify the differences between each option, you will be less likely to get confused when preparing explanatory materials later.

Points to Note for Using the PVSyst Manual in Practice

To master the PVSyst manual in practical work, it is more important to grasp the workflow where project creation tends to fail than to try to memorize all the functions. The sequence to check first is project conditions, meteorological data, system design, shading conditions, loss conditions, and report review. If you understand this flow, even if you get lost in detailed screens, you are less likely to lose sight of which assumptions you are currently setting.

When reading the manual, be aware not only of the on-screen operation instructions but also of what each input field affects. For example, the tilt angle affects the amount of incident light, ambient temperature affects thermal losses, and string configuration affects voltage conditions and inverter operation. Wiring losses relate to the loss of generated power before it reaches the output side. Understanding the meaning of each item and how it influences outcomes turns operation into more than just a task.

Also, in the initial stages it is important not to aim for perfect inputs. In the preliminary assessment phase, the priority is to first establish the major assumptions correctly and capture the trend in power generation. After that, as the design becomes more concrete, refine the equipment specifications, wiring, shading, and loss conditions in detail. If you focus too much on the details from the beginning, you may spend time on conditions that have not yet been decided, slowing down the pace of the assessment.

On the other hand, basic conditions that are difficult to change later need to be confirmed early. The installation location, meteorological data, project objectives, and comparison criteria can affect later stages if they are significantly wrong at the initial stage. In particular, errors in meteorological data or the installation location affect the overall power generation, so they should be checked carefully at an early stage. When operating while referring to the manual, be mindful of how the conditions you set initially will be reflected in the final report.

In practical work using PVSyst, coordination with design documents and on-site information is indispensable. By entering data while checking drawings, layout plans, site photos, shading conditions, equipment specifications, grid-connection conditions, and so on, you can reduce the gap between the simulation and the actual project. Just because data can be entered on the screen does not mean you can ignore real-world conditions. It is important to use PVSyst as a tool to organize real design conditions and evaluate them numerically.

When dealing with on-site conditions in particular, using smartphones, GNSS, point clouds, AR, and the like to grasp installation locations, obstacles, roof shapes, and the surrounding environment makes it easier to evaluate shading and layout. By comparing on-site position and shape information obtained in the field with desktop design conditions, you can make the assumptions for simulations more concrete. For example, leveraging an iPhone-mounted GNSS high-precision positioning device such as LRTK can improve the accuracy of site checks and location awareness, making it easier to carry out preliminary surveys and layout studies for solar projects.

The purpose of reading the PVSyst manual is not to memorize all functions. It is to check the necessary items as needed and to understand how the input conditions are reflected in the results. In practice, because conditions differ for each project, it is more realistic to consult the manual repeatedly while creating projects rather than reading it once and being done.

Summary

To successfully create projects using the PVSyst manual, it is important not only to follow the on-screen operation steps but also to understand the meaning of the conditions you enter. Especially important are the project's objectives and project conditions, meteorological data and installation location, system design, shading, azimuth and tilt, and the process up to report verification. If you cover these five items, even first-time PVSyst users will find it easier to organize what to check and where.

When creating a project, first decide the purpose of the simulation and clarify the project conditions. Whether it is a preliminary estimate, a design comparison, or intended for use as explanatory materials will change the required input accuracy. Next, check the installation site and meteorological data to see whether the assumptions about power generation deviate significantly from local conditions. Based on that, organize the modules, inverters, string configuration, and capacity settings, and input conditions that are close to the actual design.

Furthermore, azimuth angle, tilt angle, and shading conditions have a major impact on energy generation and losses. If the reference for angles is mistaken or shading is underestimated, the results may diverge from reality. After the simulation, it is important not to judge solely by the annual energy generation, but to check monthly trends, the breakdown of losses, and the consistency of the assumptions. The figures in the report are the results for the input conditions, and they can only be used for practical decision-making once those conditions have been correctly organized.

PVSyst is feature-rich, so it may feel difficult at first. However, if you understand the workflow for creating a project and preemptively address the items that are prone to errors, it becomes easier to use the energy yield simulation for design studies and comparative materials. The PVSyst manual should not be read merely as an operations guide; it is important to use it as a verification tool to correctly enter project conditions and interpret the results.