How to Run a Simulation in PVSyst｜Understand the Workflow in 3 Minutes

Table of Contents

• What to understand first about PVSyst simulations

• Input information to prepare before the simulation

• Process from project creation to setting basic conditions

• Approach to configuring the power generation equipment

• Check shadows and losses to improve the reliability of results

• Final checks before running the simulation

• Key points to check in the results report

• Common mistakes and how to avoid them in practice

• Improving the accuracy of on-site conditions determines the quality of power generation assessment

• Summary

What to Understand First in PVSyst Simulations

The purpose of running simulations in PVSyst is to predict, based on the design conditions, how much electricity a photovoltaic (PV) system can generate over a given period. It is used not merely to produce a number for energy output, but to identify which conditions affect generation, which losses are significant, and whether the system capacity and layout are reasonable.

In practical work, power generation simulations are required in various situations such as initial studies, basic design, detailed design, internal briefings, client presentations, materials for financial institutions, and pre-construction verification. Therefore, what is important in using PVSyst is not only remembering how to operate the screens. It is essential to understand which input conditions affect the results, which values should be obtained from on-site surveys and design drawings, and how to interpret the results.

PVSyst simulations, broadly speaking, proceed in the following flow: choose the location, select the meteorological conditions, enter the system conditions, set the layout and orientation, account for shading and losses, run the calculations, and review the results. What beginners often stumble over is entering detailed setting screens without being aware of this order. If you first understand the overall flow, you will know what is being decided on each screen and can reduce input errors and omissions.

Also, the results from PVSyst strongly depend on the quality of the input conditions. Even with the same system capacity, changes in installation location, tilt angle, azimuth, the presence or absence of shading, topography, surrounding obstacles, loss conditions, temperature conditions, and wiring conditions will affect annual energy production and loss rates. In other words, to improve the accuracy of the simulation, not only the operations within the software but also how site information is collected are important.

When running a simulation in PVSyst for the first time, you don’t need to aim for a perfectly detailed design from the outset. First, perform a single calculation under standard conditions and learn how to interpret the results report. After that, by gradually making factors such as shading, losses, layout, and equipment specifications closer to reality, it becomes easier to grasp how much each input affects the results.

Input information to prepare before running the simulation

Before using PVSyst, there is certain information you should prepare at a minimum. The first thing required is information about the installation site. Latitude, longitude, elevation, the surrounding environment, and meteorological conditions form the foundation of energy production calculations. If the site configuration is significantly off, the solar irradiance and temperature conditions will not match reality and will affect the overall simulation results.

Next, what is needed are the basic specifications of the power generation equipment. Organize the solar panel capacity, number of panels, installation angle, orientation, PCS capacity, connection configuration, and the assumed equipment capacity. In practice, simulations are sometimes performed before the final specifications are confirmed. Even in that case, deciding on a tentative capacity, tentative layout, and an assumed angle makes it easier to carry out comparisons in the initial review.

Furthermore, information about the site's topography and obstacles is also important. If there are buildings, trees, mountains, slopes, rows of mounting racks, utility poles, fences, etc. nearby, shadows will occur depending on the time of day and season. Simulations that ignore the effects of shading can overestimate actual power generation. In particular, in locations where shading occurs during periods of low solar altitude or in winter, it is necessary to take shading into account from the layout planning stage.

Loss parameters should also be prepared. There are multiple factors that reduce power generation, such as losses due to wiring, temperature-related losses, mismatch, soiling, degradation, downtime, conversion efficiency, and utilization. In the initial stage, standard values may be used, but when used for detailed design or presentation materials, it is desirable to use figures that are supported by evidence.

Also, you need to clarify the purpose of the simulation in advance. The required level of input detail varies depending on whether you want to know an approximate annual energy generation, compare multiple proposals, check the impact of shading, assess the appropriateness of PCS capacity, or explain the breakdown of losses. If you proceed with the settings while the objective is vague, you will not be able to understand the basis for evaluation even after seeing the results.

To learn how to use PVSyst efficiently, it is effective to organize the input information in advance and to focus on verifying and applying it within the software. By organizing, one by one, the installation site, meteorological conditions, system capacity, layout, shading, losses, and the intended use of the output reports, the work up to running the simulation becomes smoother.

Workflow from Project Creation to Basic Condition Settings

When starting a simulation in PVSyst, first create a project and set the installation location and basic conditions. The information set here will serve as the basis for subsequent system configuration and energy production calculations. It is convenient to give the project name or case name a clear, easy-to-understand title so it is easy to compare multiple cases later.

First, set the installation site. When you specify the installation location, the simulation can proceed using weather conditions appropriate to that area. Weather data have a large impact on power generation. Because solar irradiance, ambient temperature, and seasonal variations affect the calculations, it is important to choose conditions as close as possible to the target site. Even if a location is nearby, conditions can differ in mountainous areas, coastal areas, urban areas, or regions with snowfall. Therefore, in addition to selecting a nearby site, also verify that it does not significantly contradict the local meteorological characteristics.

Next, select the type of system. The approach to configuration differs depending on whether it is a typical grid-connected photovoltaic installation or a configuration that includes batteries or standalone power sources. In practice, the most common case is verifying the annual energy output of generation equipment connected to the grid. In that case, focus the settings on the solar panels, PCS, connection configuration, orientation, tilt, and losses.

Orientation (azimuth) and tilt angle are also important basic conditions. Orientation indicates which direction the power generation equipment faces, and the tilt angle indicates the installation angle of the panels. In general, when orientation or tilt changes, the power generation by time of day and the annual generation change. Because results vary depending on installation conditions—such as south-facing, east- or west-facing, low tilt, or high tilt—these settings should be made together with the on-site layout and racking plan.

After creating a project, it is recommended to first proceed until you can run a simulation under standard conditions. If you focus too much on the details, you may not be able to determine where an error is occurring. At first, enter only the location, weather conditions, system capacity, orientation, tilt, and basic losses, and verify that the calculation runs successfully. After that, add shading and detailed losses so you can check the impact of each setting step by step.

PVSyst simulations may look difficult because there are many input items, but in reality they are a process of sequentially reflecting the site conditions and equipment conditions that affect energy production. If you are aware of which input corresponds to which assumption, you will be less likely to get confused when navigating the interface.

Approach to Setting the Configuration of Power Generation Equipment

Once you have set the basic conditions, next enter the configuration of the power generation equipment. Here you determine the specifications and number of solar panels, the PCS specifications, the connection configuration, the capacity relationship between the DC side and the AC side, and so on. When running a simulation in PVSyst, this equipment configuration directly affects the results.

The first thing to check is the capacity and number of solar panels. The installed capacity is determined by the output per panel and the number of panels. If the capacity you enter differs from the actual design proposal, the annual power generation will of course change. Since multiple proposals are often compared in the early stages of design, managing proposals with different capacities separately makes it easier to compare them later.

Next, set the PCS capacity. PCS is equipment that converts direct current power to alternating current power, and the capacity setting affects generation and output limits. Determining how large the PCS capacity should be relative to the solar panel capacity is an important design consideration. If the DC-side capacity is made relatively large, output can reach its upper limit during periods of strong insolation, and some limiting may occur. On the other hand, excessively increasing PCS capacity does not necessarily improve the overall balance of the installation. In PVSyst, you can check the effects of these capacity ratios.

Connection configuration is also important. If the number of strings, the number of modules in series, or the assumptions about the input circuit do not match the actual system, problems can arise with the voltage range or operating conditions. In PVSyst, you can proceed while verifying whether the configured setup is electrically valid. If a warning is displayed, do not simply ignore it; check which condition is causing the problem.

In practice, panel layout and electrical configuration are sometimes considered separately. However, in simulations the two are connected. Even if panels can be placed on the layout, if the string configuration or PCS input conditions do not match, the design may not be feasible in reality. Therefore, when entering the configuration in PVSyst, we align the layout on the drawings, the system capacity, and the electrical design assumptions as much as possible.

Temperature conditions also affect power generation. Solar panels have the characteristic that their output decreases as temperature rises. The degree of temperature increase varies depending on the installation method, ventilation, racking height, and whether they are installed on a roof or on the ground. Standard settings may be used at the initial stage, but if they differ significantly from actual conditions, they should be reviewed.

When configuring power generation equipment, it is important not to set things up solely to make the calculations run. By proceeding while verifying that the entered configuration matches a real design proposal, that capacity ratios are reasonable, that there are no warnings in the connection configuration, and that the settings can be explained later, the credibility of the simulation results is enhanced.

Verify shadows and losses to improve the reliability of the results

When running energy yield simulations in PVSyst, the settings for shading and losses are extremely important. Even if you only enter the installed capacity and meteorological conditions, if site-specific shading and equipment-specific losses are not reflected, the results may be more optimistic than reality.

The effects of shading include shadows from surrounding obstacles and shading between rows of panels. Surrounding obstacles include buildings, trees, mountains, slopes, walls, and equipment. The length and direction of these shadows change with the season and time of day. In particular, during mornings and evenings and in winter, the sun’s altitude is lower, so shadows can extend farther than anticipated.

Shading between panel rows is also important for both ground-mounted and rooftop installations. When row spacing is narrow, shadows from the front row fall on the rear rows, reducing power generation. If you try to place as many panels as possible within a limited area, capacity may increase but shading losses can also rise. In PVSyst, by checking the layout conditions and the effects of shading, you can consider the balance between simply maximizing capacity and optimizing generation efficiency.

In loss settings, consider wiring losses, conversion losses, temperature losses, soiling, mismatch, degradation, downtime rate, and so on. You don't necessarily have to specify every loss in detail, but by looking at the breakdown of losses in the result report you can see which factors have the greatest impact on power generation. In practice, it is important to be able to explain the rationale for the losses. When using this for internal reviews or customer explanations, it's reassuring to be able to explain why those loss rates were adopted.

A common mistake beginners make is calculating with the default initial values and using only the results. The initial values do not necessarily match the project at hand. For example, in environments prone to soiling, regions with snowfall, locations where salt damage is a concern, or areas with many obstacles nearby, standard conditions alone may not accurately reflect the actual site conditions.

However, that doesn't mean you should assume excessive losses. Imposing overly stringent conditions without justification can make the equipment's profitability and planning decisions look worse than they actually are. The important thing is to set reasonable values for the site conditions, design conditions, and operating conditions.

The strength of PVSyst simulations is their ability to handle shading and losses in detail. However, that also means the judgments made by the person entering the data are reflected in the results. For that reason, shading and losses should not be items casually added at the end, but must be treated as primary factors that determine the quality of an energy yield assessment.

Final check before running the simulation

Before running the simulation, review all input conditions. In PVSyst, if there are contradictions in the settings or conditions that require attention, warnings or messages may be displayed. These may not only indicate critical errors that would stop the calculation, but also highlight points that should be checked from a design perspective.

The first things to check in the final review are the installation site and the meteorological conditions. Confirm that the location is not significantly different from the project site and that the elevation and weather data are not anomalous. If the location is different, solar irradiance and temperature will change, affecting power generation. If there are multiple candidate sites, be prepared to explain why you chose the site.

Next, check the azimuth and tilt angles. Verify whether they match the drawings and on-site conditions, and ensure that east–west orientations or multi-plane layouts are correctly reflected when present. Mistakes in entering the azimuth angle are a common error that can greatly affect the results. Also confirm that the tilt angle corresponds to the roof pitch or the racking angle.

We always check equipment capacity as well. We verify that panel capacity, the number of panels, PCS capacity, and the connection configuration match the assumptions. Mistakes in units or omissions of the number of panels can greatly change the resulting power generation. In particular, when creating multiple proposals, be careful to ensure that settings from a previous proposal have not been left in place.

We will also review the settings for shading and losses. Even if you believe you have applied a shading model, it may not be reflected in the calculations or the coverage may be insufficient. Also confirm whether the loss rate remains at the initial value or has been adjusted to match the project conditions. For items that will need to be explained in the results report, organizing the rationale before execution will make later processes easier.

If a warning message appears, read its content and make a judgment. A warning does not necessarily mean that the calculation cannot be performed, but it may indicate that the design conditions are abnormal. For example, warnings regarding voltage range, capacity ratio, input conditions, or temperature conditions should be checked carefully, as they can also affect actual equipment design.

The final check is not merely a task confirmation but a process to treat simulation results as reliable documentation. By making a habit of verifying location, weather, azimuth, tilt, system capacity, connection configuration, shading, losses, and warnings before pressing the run button, you can greatly reduce rework.

Key Points to Check in an Execution Results Report

When you run a simulation, you can check annual energy production, monthly energy production, loss breakdown, performance ratio, system conditions, and more. Because PVSyst’s result reports contain a large amount of information, beginners can easily be unsure where to look, but in practice it becomes easier to understand if you review several key items in order.

The first thing to look at is the annual energy output. This is a representative value that indicates how much electricity the facility is expected to generate over the course of a year. However, it is risky to judge quality based solely on the annual output. Because a larger installed capacity will produce more generation, you need to check it together with generation per unit of capacity and performance indicators.

Next, check the monthly power generation. By looking at monthly variations, you can understand seasonal generation trends. Generation increases during periods with favorable solar radiation, and fluctuations appear during periods with low solar radiation or when temperature conditions have a large impact. If a particular month is significantly lower, you need to check for shading, snowfall, configuration errors, or the effects of weather conditions.

The breakdown of losses is also important. If power generation is lower than expected, checking which losses are large can reveal opportunities for improvement. If shading losses are large, there may be room to reconsider the layout and row spacing. If temperature losses are large, it is necessary to consider the installation environment and ventilation conditions. If wiring losses are large, it may be necessary to review the wiring plan and equipment layout.

The performance ratio is an indicator used to understand how efficiently an installation is generating electricity. A higher value is not necessarily always better, but it is useful when comparing proposals in the same region or with similar installation conditions. If the value is extremely low, check whether there are problems with the input conditions, loss conditions, shading, or system configuration.

Also, the report will include the input conditions. By checking these, you can reconfirm the assumptions on which the simulation results are based. Instead of extracting only the power generation figures, it is important to view them together with the installation location, weather conditions, system capacity, azimuth, tilt, and loss conditions. When using it as documentation in practice, it is important that the basis for the results can be traced within the report.

With simulation results, how they are interpreted as decision-making material is more important than the raw numerical outputs. A proposal with higher power generation is not always optimal. It is necessary to consider constructability, maintainability, shading risk, terrain conditions, equipment costs, and future operations. PVSyst reports should be used as technical documentation to support those decisions.

Common Mistakes and How to Avoid Them in Practice

One common mistake when using PVSyst is using only the results without sufficiently checking the input conditions. Simulation results are based on the assumption that the input conditions are correct. If the installation location, azimuth, tilt, system capacity, or loss conditions are different, the results will be different. It is important to make a habit of checking the assumptions before the results.

Another common problem is that the conditions are not consistent when comparing multiple options. For example, even if you intend to change only the system capacity between Option A and Option B, the comparison won’t be fair if loss conditions or shading settings differ in just one of them. When carrying out a comparative evaluation, keep all conditions as identical as possible except for those you want to change, and make it clear which change in conditions produced the results.

Postponing the shading settings can also lead to failure. While shadows may be simplified during initial assessments, the impact of shading cannot be ignored at sites with many nearby obstructions. A plan that looks promising in terms of power generation can still produce significant shadows in the morning and evening when you visit the site. Especially for plans that maximize the installation area—from low-voltage systems to large-scale facilities—it is important to check inter-row shading and shading from surrounding terrain early.

A further point of caution is failing to adequately consider the relationship between PCS capacity and panel capacity. The balance between DC-side and AC-side capacity affects energy generation, output limits, and system configuration. Changing the capacity ratio can alter annual energy generation and the breakdown of losses. Rather than simply assuming that increasing capacity is always better, it is necessary to verify the overall system efficiency and how constraints will manifest.

You should also avoid setting loss rates without justification. Even when using standard values, consider whether they are appropriate for the project at hand. At sites prone to soiling, sites influenced by vegetation, sites with potential salt damage or snowfall, or sites where maintenance frequency is limited, relying solely on standard conditions may be insufficient.

Furthermore, in practice it is useful not to stop after producing simulation results just once, but to vary the conditions and perform a sensitivity analysis. By checking how the results change when the tilt angle is altered slightly, when the row spacing is changed, when the PCS capacity is varied, and when shading is or is not taken into account, you can strengthen the basis for design decisions.

PVSyst is a high-performance simulation tool, but it does not automatically guarantee correct results. Only when the user understands the site and design conditions, sets reasonable assumptions, and interprets the results does it become a document usable in practice.

Improving the accuracy of site conditions determines the quality of power generation assessments

If you understand the workflow for running simulations in PVSyst, what ultimately becomes important is the accuracy of the site conditions. No matter how carefully you configure the software, if the site’s topography, obstacles, available installation area, orientation, elevation differences, or the locations of surrounding structures are unclear, the reliability of the results will be limited.

In planning solar power generation facilities, even if the drawings appear fine, there can be unexpected changes in elevation and obstacles on site. Small level differences, slopes, trees, existing equipment, surrounding buildings, fences, utility poles, and the like can affect shading and layout. Especially for ground-mounted installations, terrain undulations also influence panel arrangement, site formation plans, drainage planning, and maintenance access routes.

PVSyst's power generation simulation calculates based on the design conditions entered. Therefore, the more accurate the on-site surveying and understanding of actual conditions, the closer the conditions input into the simulation will be to reality. Conversely, if site information remains ambiguous, the simulation figures may look clean but discrepancies can arise during the construction or operational phases.

For practitioners, it is important not to limit simulations to desk work alone. Obtaining on-site coordinates, elevations, installation boundaries, obstacle locations, photographic records, and point cloud data, and cross-checking them against design conditions, increases the persuasiveness of energy yield assessments. Even when shading is a concern during layout studies, knowing the on-site obstacle positions and heights makes it easier to arrive at more realistic evaluations.

What is useful here is a positioning environment capable of handling high-precision location information in the field. LRTK, as an iPhone-mounted GNSS high-precision positioning device, can be used to obtain coordinates on site and link them to field information such as photos and point clouds. In the design and simulation of solar power generation systems, it is important not only to perform desktop power output calculations but also to accurately understand the on-site installation conditions. If you use LRTK to organize on-site location and terrain information before and after running simulations with PVSyst, it becomes easier to carry out the full range of tasks—from confirming design conditions, identifying shadows and obstacles, and considering layouts, to managing records before and after construction.

By calculating energy yield with PVSyst and precisely capturing on-site conditions with LRTK, you can reduce discrepancies between simulations and the actual site. Preparing not only the energy yield figures but also the on-site information that supports those figures leads to solar power project plans that are trusted in practice.

Summary

The flow for running a simulation in PVSyst is easier to understand if you view it in the order of deciding the installation site, selecting the meteorological conditions, configuring the power generation equipment, entering the azimuth and tilt, accounting for shading and losses, performing a final check, and then running the calculation. Although the on-screen operations alone may seem complicated, in reality it is the process of reflecting site conditions and equipment conditions in the energy yield calculation.

The first thing beginners should be aware of is not to focus solely on the numerical results. Annual energy production, monthly generation, loss breakdown, performance ratio, and so on are important, but they are all calculated based on input conditions. If the installation location, weather conditions, azimuth, tilt, installed capacity, PCS capacity, connection configuration, shading, and assumptions about losses are not appropriate, the reliability of the results will decrease.

When using PVSyst in practice, it's important not to stop after a single calculation but to compare results under different conditions to determine which factors affect energy production. Comparing cases such as with and without shading, different row spacings, different tilt angles, and different PCS capacities will clarify the basis for design decisions.

Also, the quality of PVSyst simulations is greatly affected by the accuracy of on-site information. To calculate power generation accurately, you need to understand as closely as possible the installation area, topography, obstacles, orientation, elevation differences, and so on. If site conditions remain unclear, no matter how detailed the software settings are, discrepancies with actual construction and operation will remain.

PVSyst is an effective tool for organizing the workflow of power generation simulations and comparing design proposals. To bring those results closer to real-world practice, high-precision local positioning information and records are indispensable. By using an iPhone-mounted high-precision GNSS positioning device like LRTK, you can efficiently obtain local coordinates, topography, and photographic records, making the evaluation conditions in PVSyst more reliable. By combining accurate power generation forecasts with precise site information, planning, design, construction, and maintenance of photovoltaic power systems can proceed more smoothly.