8 Tricky Settings in the PVSyst Manual

Table of Contents

• Prerequisites to Know Before Reading the PVSyst Manual

• Common pitfall 1: Proceeding while leaving the difference between projects and variants ambiguous

• Troublesome Setting 2: Delaying Weather Data and Site Conditions

• Common Pitfall Setting 3: Entering Azimuth and Tilt Angles by Feel

• Common Pitfall 4: Choosing Module and Inverter Combinations Without Sufficient Verification

• Common Pitfall Setting 5: Continuing to use the loss conditions at their initial values

• Common pitfall 6: Configuring shadow analysis only superficially

• Common pitfall 7: Comparison criteria for multiple options are not aligned

• Common Pitfall 8: Misreading Report Results

• Approach to Mastering the PVSyst Manual for Practical Use

Prerequisites You Should Know Before Reading the PVSyst Manual

Many people who consult the PVSyst manual want to proceed with simulations of photovoltaic systems, but are unsure where to start configuring settings, which parameters to modify to influence the results, or what to check when errors or warnings appear. PVSyst has many input fields and presents technical terms on each screen, so simply reading the manual from top to bottom does not always lead to practical decision-making.

PVSyst's project design proceeds with the concept of creating a project that contains site conditions and meteorological data, and managing multiple simulation conditions within it as variants. The official documentation likewise describes the workflow of performing PV system design and performance analysis through detailed simulations, and treating different simulation runs as variants.

Therefore, the first thing to focus on in the PVSyst manual is not memorizing the operational steps. Rather, you should separately understand which settings affect energy output, which settings relate to managing comparison conditions, and which settings directly determine the reliability of the report. If you proceed without organizing this, even if the simulation itself is completed you will later be unable to explain why those results were obtained.

The eight areas people particularly tend to stumble on are initial setup, azimuth, tilt angle, system configuration, loss conditions, shading conditions, comparison settings, and report review. Because these are configured on separate screens, beginners in particular tend to treat each one as an independent input field. In reality, however, they are all connected. If the site conditions change, the judgment of the optimal tilt angle changes; if the combination of module and inverter changes, the apparent voltage conditions and losses change; and if shading conditions are handled poorly, the interpretation of energy production and loss charts also changes.

In this article, we divide the settings that are easy to get stuck on in the PVSyst manual into eight patterns and organize the considerations to verify in practice. Rather than chasing the exact names of minor buttons on the screen, first understanding "what the setting is meant to determine" will greatly change how you read the manual.

Common Pitfall 1: Proceeding with an unclear distinction between a project and a variant

One of the first things people often stumble over is the difference between a project and a variant. In PVSyst, the overall assumptions for an entire case are treated as a project, and within that project design proposals and differing conditions are managed as variants. For example, assuming the same site and the same meteorological conditions, if you want to compare a proposal that changes module capacity, a proposal that changes the tilt angle, and a proposal that adds shading conditions, the idea is to separate and manage each of those as a variant.

If you proceed without clarifying this, the conditions you want to compare will get mixed up. For example, if in the first scenario you change the meteorological data, in the next scenario you change the tilt angle, and in another scenario you change the loss settings, you will not be able to determine which factor caused the final difference in energy output. Looking only at the simulation results will show numerical differences, but if you cannot explain the causes of those differences, the results will be difficult to use for design studies or internal reviews.

When reading the PVSyst manual, it is important to first understand that a project forms the foundation of a case and that a variant is the unit for examining different conditions. The official documentation also shows a workflow in which you first define the system configuration with minimal conditions and then create variants that add elements such as far shading, near shading, and loss parameters, and compare them.

In practice, it is safer not to try to include all conditions from the start. First, create a base proposal using only the site, meteorological data, and the basic system configuration, and save the results. Next, sequentially create proposals that change the tilt angle and azimuth, include shading conditions, and adjust loss conditions to be closer to on‑site assumptions. By dividing the process into these stages, it becomes easier to trace how much each setting change affected the results.

A common mistake beginners make is entering all changes into a single variant while following the manual. Filling in the input fields itself becomes the goal, and when you try to compare later, there is no baseline left. While PVSyst can perform detailed simulations, if users do not consciously organize the configuration history, the evaluation process becomes opaque.

As a countermeasure, include the changes in the variant name. For example, basic plan, tilt-angle-change plan, added shading-conditions plan, and revised-losses plan — so that you can tell what was changed just from the name. Because the number of variants increases as the project progresses, deciding on a naming rule at an early stage will make it less confusing when you review the manual.

Common setup mistake 2: Putting off meteorological data and site conditions

When evaluating power generation with PVSyst, meteorological data and site conditions are extremely important. However, beginners in particular tend to want to start by tweaking module and inverter settings and often put off selecting meteorological data and checking site conditions. This is a major stumbling block.

In solar power generation simulations, solar irradiance, ambient temperature, seasonal variations, and the latitude and longitude of the installation site affect the results. If the meteorological data are significantly different from the actual installation site, no matter how finely you configure the system components, the assumptions behind the predicted energy production will be off. When reading the PVSyst manual, you should make it a priority to confirm that the site and weather conditions are correctly set before addressing the system components.

A common mistake here is being satisfied with simply selecting a nearby region name. For example, even within the same prefecture, meteorological conditions differ between coastal, inland, and mountainous areas. Factors to consider vary by project, such as snowfall, fog, sea breezes, high temperatures, and the influence of surrounding terrain. Just because there is data you can select on PVSyst's screen doesn't mean it is optimal for that project.

Also, if site conditions are changed partway through, it can become difficult to compare with existing variants. If the meteorological data differ between the initial proposal and the subsequent one, it becomes hard to determine whether differences in power generation are caused by design changes or by differences in weather conditions. When comparing simulation results, you must clearly specify which conditions are kept common among the variants being compared and which conditions are changed.

In practice, before selecting meteorological data you should confirm the project's purpose. Whether it is a preliminary estimate, a design comparison, or the preparation of materials to explain to financial institutions or the client, the required level of accuracy and the responsibility for explanation will differ. For early-stage rough estimates, checking general trends may be sufficient, but the closer the work gets to a formal study, the more you need to be able to explain the source of the meteorological data and the reasons for its selection.

When using the PVSyst manual, it is important not to treat the meteorological data selection screen as a mere data-entry task, but to view it as the step that sets the assumptions for energy production. Carefully checking this area makes it easier later to determine whether a higher- or lower-than-expected energy output is due to a settings error or natural variation in site conditions.

Common Setup Pitfall 3: Entering Azimuth and Tilt Angles by Feel

Azimuth and tilt angles are basic settings that must always be checked in the PVSyst manual. However, beginners in particular tend to enter them with a mindset like "south-facing is fine" or "just match the roof pitch." Of course, for rooftop installations you need to follow the actual roof geometry, but even so it is essential to understand the impact that the input values have on the simulation results.

In PVSyst, a simple optimization feature is available in the definition of fixed surfaces to check trends in energy production according to tilt and azimuth. The official documentation also explains that, for fixed surfaces, a quick optimization tool showing energy yield as a function of tilt and azimuth allows one to assess how much the chosen orientation affects results compared with the optimal conditions.

What’s important here is that aligning solely with the optimal value is not necessarily the correct approach. For ground-mounted systems it is relatively easy to consider the tilt angle that maximizes generation, whereas rooftop installations have constraints such as roof pitch, building constraints, constructability, loads, aesthetics, and wind conditions. In agrivoltaic systems and snowy regions, factors like sunlight for crops, snow shedding, and racking height also come into play. In other words, the optimization results in PVSyst are material for design decisions and should not be adopted as-is.

A common pitfall is misinterpreting the reference for azimuth angles. If the coordinate system used by the software or drawings, the notation in design documents, and the azimuth representation in site surveys do not match, the orientation of the input values can be off. For example, if you enter values without confirming differences such as "which east–west direction is considered positive," "whether true south is used as the reference," or "whether north is defined as 0 degrees," the simulation may run with an orientation different from what you intended.

The same applies to slope angles. You cannot always enter the gradient notation on the drawing directly as an angle. If the roof pitch is expressed as a rise-to-run ratio, it must be converted to an angle. The angle measured on site, the pitch shown on the design drawings, and the as-built measurements after construction may differ slightly. It is important to record which value was adopted and why that value was used.

When reading the PVSyst manual, you should consider not only the screen where you enter the azimuth and tilt angles but also the preliminary review of reference materials used to determine those values. Simulations produce results that faithfully reflect the conditions entered, but if the input values differ from reality, the results will of course be off. Understanding this lets you, when analysis results do not match, review not only equipment settings and loss assumptions but also the assumptions about orientation and tilt.

Common setup pitfall 4: Choosing a module and inverter combination without sufficient verification

One of the next stumbling blocks in the PVSyst manual is the combination of modules and inverters. In photovoltaic system design, module capacity, string configuration, inverter capacity, input voltage range, maximum voltage, and the oversizing ratio are all related. PVSyst allows you to configure these in detail, but because there are so many items, some people assume that it's fine as long as no warnings appear.

However, the absence of warnings does not mean the design is appropriate in practice. For example, increasing the number of modules may appear to increase energy production, but depending on its relationship with inverter capacity, output clipping can occur at peak times. Conversely, giving the inverter too much headroom can create other issues in terms of cost and operation. In PVSyst settings, you need to proceed while checking these design trade-offs.

The official documentation explains, within the project settings, items such as the maximum array voltage related to the open-circuit voltage at minimum temperature and the allowable level of overload loss used for inverter sizing. These items are not mere detailed settings but important checkpoints that affect safety, equipment specifications, and power generation assessment.

A common pitfall is proceeding by simply selecting a similar model number from the component database. The module and inverter model numbers, ratings, temperature coefficients, input ranges, number of MPPTs, etc., need to be checked against the specifications of the actual equipment to be used. Even devices with similar names can have different specifications. This is especially true for products from overseas manufacturers or different generations, where part of the model number may be the same but the ratings differ.

Also, confirming the string configuration is important. If the number of modules in series is too low, under low irradiance or high-temperature conditions the inverter may have difficulty operating within its permissible range. If the number of modules in series is too high, the open-circuit voltage at low temperatures may approach the maximum allowable voltage. Do not rely solely on checks in PVSyst; you need to verify against the equipment datasheets and design standards to be used.

In practice, the countermeasure is to organize a list of the modules, inverters, number of strings, number of modules in series, orientation-specific inputs, and capacity ratios before deciding the system configuration. Rather than thinking about it after entering data into PVSyst, you should first confirm that the design proposal is valid and then reflect it in PVSyst, which will reduce errors.

When reading the PVSyst manual, you should view the system settings not as a "device selection screen" but as a "screen for verifying whether the configuration is electrically valid." Simply having this awareness makes it easier to understand the meaning of warnings and the loss items in the report.

Common Pitfall 5: Continuing to Use Loss Settings at Their Default Values

What greatly influences PVSyst results are the various loss parameters. In photovoltaic power generation, many losses add up, such as soiling, wiring, mismatch, temperature, degradation, equipment performance, shading, and inverter losses. Even when reading the PVSyst manual, many people are likely to be unsure how far they should adjust the loss items because there are so many.

A common stumbling block for beginners is continuing to use initial values as they are. Initial values are convenient as a starting point for running simulations, but they are not the optimal values for every project. For example, areas with a lot of dust, coastal locations, snowy regions, high-temperature zones, farmland surroundings, or factory roofs experience different effects from soiling, temperature, and the surrounding environment. Using loss settings that do not match site conditions can make the results either overly optimistic or overly pessimistic.

In the official documentation, array losses are described as effects such as the deviation of actual module performance from manufacturer specifications, mismatch losses between modules, and losses related to energy that cannot be utilized. In other words, loss conditions are settings to express how the actual installation deviates from the ideal state, not simply coefficients that slightly reduce power generation.

Wiring losses are another item that is easily overlooked. Wiring losses vary depending on cable length, voltage, current, routing, and the placement of combiner boxes and power conditioners. During the estimation stage, standard values may be used, but as the design becomes more concrete, it is necessary to align more closely with the actual wiring plan. The approach to wiring distances differs between roof-mounted and ground-mounted installations.

Temperature losses are also important. Module temperature is affected not only by ambient temperature but also by the installation type, ventilation, roofing material, and racking height. Installations mounted flush to the roof and installations on the ground with ensured ventilation will see different increases in module temperature even in the same area. When checking temperature-related settings in PVSyst, you need to consider the installation method together with the site environment.

When setting losses, what matters is not entering every detail but being able to explain the rationale for the values you adopt. Even at stages when you cannot measure everything precisely, if you document why you used each value, which sources or empirical data you based it on, and when you will review it, you will make it easier to improve the accuracy of your analysis later.

When reading the PVSyst manual, do not treat loss settings as merely a matter of "filling in input fields." Losses are adjustment factors that bring simulation results closer to reality and are important settings that reflect the site-specific conditions of each project.

Common Pitfall 6: Setting Up Shadow Analysis Superficially

Many people struggle with shading analysis in PVSyst. In particular, near shading is a part that’s hard to grasp even after reading the manual, because it involves creating 3D scenes, placing obstacles, the relationship with module surfaces, and handling electrical impacts. The official documentation also treats near shading as one of the most difficult aspects of PVsyst and provides a tutorial explaining the procedures and how to use it.

A common stumbling block in shadow analysis is being satisfied with simply placing an obstruction. In reality, losses vary depending on the obstruction’s height, position, orientation, distance to the module plane, seasonal solar altitude, time of day, and the area affected by shadows. Even if it looks plausible in 3D, if the dimensions or positional relationships differ from reality, the calculated results will be off.

In near-field shading, it is also important how the effects on the direct, diffuse (scattered), and albedo components are each handled. The official documentation explains that the calculation of near-field shading is performed at each time step and applied in different ways to the direct, diffuse, and albedo components. Therefore, shading settings need to be understood not merely as geometry creation but as settings that affect how solar radiation is treated.

Also, dealing with electrical losses caused by shading is another common pitfall. Even if the same area is shaded, the impact on power generation varies depending on how the shading affects the string. When part of a module is shaded, you cannot simply judge losses by the proportion of shaded area. When using PVSyst’s shading analysis, you need to be aware not only of the 3D geometry but also of the electrical connection configuration.

In practice, before conducting shadow analysis, you decide which shadows to model and to what extent. Shadow-causing factors are diverse: surrounding buildings, rooftop equipment, guardrails, spaces between racking rows, trees, utility poles, mountains, and terrain. Trying to include every detail makes the workload excessive, but omitting factors that significantly affect power generation undermines the reliability of the results. It is important to assess the significance of shadows.

To avoid superficial shadow settings, first organize site and drawing information and identify the main obstacles. Next, confirm how shadows move with the seasons and different times of day. Then reflect this in the 3D scene in PVSyst and check the extent of shading loss. If the results are excessively large or small, review the obstacles’ dimensions and positions, their azimuth, and the module plane settings.

When reading the shading analysis section of the PVSyst manual, you should be aware not only of how to operate it but also of how the shapes you input lead to the loss calculations. Shading analysis is not about reproducing appearance; it is a process to make the impact on power generation more realistic.

Common Pitfall 7: Comparison conditions for multiple options are not aligned

PVSyst is useful for comparing multiple design options, but if the comparison conditions are not aligned you cannot correctly judge the results. A common pitfall is believing you have created several options for comparison when, in fact, conditions other than the items you want to compare have been changed.

For example, if you want to compare different tilt angles, you need to keep the weather data, modules, inverters, loss conditions, and shading conditions as consistent as possible. If the module capacity is changed at the same time, you cannot determine whether the difference in power output is due to the angle or the capacity. If the inverter type has also changed, interpretation becomes even more difficult.

When making comparisons, it is also important to decide the evaluation criteria. Your judgment will change depending on whether you look only at annual energy generation, specific yield (generation per unit capacity), performance ratio, loss diagrams, or monthly trends. A proposal with the largest annual generation is not always optimal. Although greater capacity increases total generation, when considering efficiency, cost, constructability, and constraint conditions per unit capacity, a different option may be more advantageous.

In PVSyst reports, you can check not only the simulation results but also the breakdown of losses. The official documentation also explains that loss diagrams are useful for identifying weaknesses in system design, and that the engineer’s report for each simulation run can include the parameters used and the key results. Therefore, in comparisons it is important to look not only at the amount of energy produced but also at which losses are increasing or decreasing.

In practical comparisons, first clarify the baseline proposal. Next, create versions that change one condition you want to compare at a time. If comparing tilt angles, change only the tilt angle; if comparing equipment, change only the equipment; if comparing shadow mitigation, change only the shadow conditions or the layout. Of course, in actual design multiple conditions may change simultaneously, but even then, if you have a record of stepwise examinations, it becomes easier to explain the reasons behind the final proposal.

Also, when explaining comparison results, you need to present not only the numerical values but also the underlying assumptions. Even if the annual energy production is the same, its meaning changes if the configuration settings differ. When checking the report and variant items in the PVSyst manual, it is important to do so with the premise of creating comparison tables and to be mindful of which conditions you keep fixed and which you change.

To avoid stumbling, briefly record the changes each time you add a variant. When you look back later, knowing what each option was created for makes organizing reports and explaining matters to stakeholders much easier.

Common Pitfall 8: Misreading Report Results

A common stumbling block at the end is how to interpret the report results. PVSyst displays many numerical values after a simulation. Because there are so many items to look at — annual energy production, monthly energy production, performance ratio, loss diagram, and various energy indicators — beginners in particular tend to judge results by only the most prominent figure.

However, the report is not just for confirming the amount of power generated. It is a document for determining under what conditions the calculations were made, where losses are occurring, what the design weaknesses are, and how it differs from alternative proposals. Even if the annual energy production is close to expectations, an unnatural breakdown of losses may indicate an error in the input conditions.

For example, if shading losses are extremely small, you need to verify whether the impact of shading is truly minimal or whether the shading condition inputs are insufficient. If temperature losses differ from expectations, review whether the mounting configuration and temperature condition settings reflect the actual situation. If inverter losses or overload losses are large, recheck the capacity ratio and the string configuration. A report is not merely a place to receive results, but also a place to validate the input conditions.

Performance ratio also requires attention. The performance ratio is a useful indicator for understanding system efficiency, but it should not be used alone to determine whether something is good or bad. Because it varies with site conditions, temperature conditions, shading, capacity ratio, loss settings, and so on, it is important to compare it with projects under similar conditions or with variants within the same project.

Monthly results should not be overlooked. Annual values alone do not reveal seasonal biases. If power generation drops sharply in winter, you need to check solar irradiation conditions, snow cover, shading, tilt angle, and surrounding topography. If output in summer is lower than expected, temperature losses or inverter output limitations may be affecting it. Even if the annual value seems reasonable, if the monthly trend looks unnatural, there is room to review the settings.

When reading the PVSyst manual, it is more effective to decide the order in which to check things than to memorize the meaning of each report item one by one. First confirm whether the input conditions are as expected, then look at the annual energy production and monthly trends. After that, check the major loss items in the loss diagram, and finally look at the differences with the comparison cases. Following this order makes it less likely that you will be swayed by numbers alone.

Also, when presenting a report externally, you must communicate not only the results but also the assumptions. You need to indicate which meteorological data were used, which equipment was assumed, how loss settings were configured, and to what extent shading conditions were reflected; otherwise, the validity of the estimated energy yield cannot be assessed. PVSyst’s output is powerful, but it does not by itself constitute explanatory material. Only when users supplement it with assumptions and interpretations does it become a document usable in practice.

Approaches to Using the PVSyst Manual in Practical Work

To avoid getting stuck with the PVSyst manual, simply reading the screens in order is not enough. Because PVSyst allows for detailed inputs, if you lose sight of what each setting is intended to achieve, you may end up focusing only on the input tasks. What’s important is to understand the flow—project, meteorological data, azimuth angle, tilt angle, equipment configuration, losses, shading, comparison, and report—as a single design-study process.

First, clarify the roles of the project and the variant. The project forms the foundation of the case, while the variant is the unit for managing different conditions. Next, verify the meteorological data and site conditions. If these are off, no matter how much you fine-tune subsequent detailed settings, the assumptions behind the results will be unstable. With that in place, set the azimuth and tilt angles, and confirm the combination of modules and inverters.

Next, adjust the loss conditions to better reflect actual site conditions. Instead of proceeding with the initial default values, consider the project's environment, mounting method, wiring plan, temperature conditions, and the effects of soiling and shading. Additionally, perform shading analysis as needed and verify how 3D scenes and electrical impacts are handled. Finally, compare multiple proposals and read the results and the breakdown of losses in the report.

By keeping this workflow in mind, the PVSyst manual becomes not just an operational guide but a checklist for design decision-making. When errors or warnings occur, it becomes easier to narrow down which group of settings is likely causing them. If the energy production is lower than expected, you can check, in order, the meteorological data, azimuth, tilt angle, shading, losses, and equipment configuration. If it is higher than expected, you can also review whether the loss settings or shading conditions are overly optimistic.

For beginners, the important thing is not to aim for perfect settings from the start. First create a basic configuration, check the results, and then add conditions one at a time—this makes it easier to understand. If you introduce complex shading and detailed losses all at once in the initial stage, it becomes difficult to see which settings are influencing the results. By configuring things step by step, it becomes easier to understand PVSyst’s underlying approach.

Also, when you change parameter values, it’s important to keep the habit of recording the reasons. If you document why you chose that meteorological data, why you set that tilt angle, why you adopted that loss rate, and why you modeled that shading element, it will be easier to review later. PVSyst results only become meaningful when paired with the input conditions.

The eight configuration patterns that are easy to get stuck on in the PVSyst manual are not solely a beginner’s problem. Even those with practical experience can overlook things when project conditions change. In particular, the settings to prioritize differ for roof-mounted installations, ground-mounted installations, agrivoltaic projects, snowy regions, high-temperature regions, battery-integrated systems, self-consumption systems, and grid-connected projects. That’s precisely why, when reading the manual, you need not only to learn the operations but also to have decision criteria tailored to each project.

A shortcut to mastering PVSyst is not to understand all of its features at once. Start by firmly grasping eight items: the project and its variants, meteorological data, azimuth and tilt angles, system configuration, loss conditions, shading analysis, comparison conditions, and report review. Once these eight are organized, it becomes much easier to see which parts of the manual you need to read, and you will reduce configuration errors and misinterpretation of results.

The PVSyst manual may look like a difficult technical book. However, the areas where people run into problems in practice can be patterned to some extent. Rather than following the input screens in order, reading it along the flow of design decisions makes it easier to find the information you need. When using PVSyst in practice, the most important goal is to be able to explain not only the energy production figures but also the assumptions those figures were based on.