What is PVSyst? Explaining 8 Input Parameters That Beginners Often Get Confused About

PVSyst is simulation software used to input design conditions for photovoltaic power generation systems and to evaluate generated energy, losses, and the validity of equipment configurations. The official notation is PVsyst, but in this article we use "PVSyst" to match the form commonly used in searches.

PVSyst is provided as PC software for the design, sizing, and data analysis of photovoltaic systems, including grid-connected, stand-alone, pumping, and DC-grid applications. In practice, it is used to forecast annual energy production, verify combinations of modules and PCS, and account for losses such as shading, temperature, and wiring.

On the other hand, for practitioners new to PVSyst, the many on-screen input fields can make it hard to know how precisely values should be entered and which values may be provisionally set. In particular, meteorological data, azimuth, tilt angle, shading, equipment configuration, strings, loss conditions, and how to read the output report are areas where input errors and misinterpretations are likely to occur.

This article explains, for practitioners searching for "What is PVSyst", the basic role of PVSyst and eight input items that beginners are likely to be confused about, from a practical perspective.

Table of Contents

• What is PVSyst used to verify?

• Input item 1: Site information and meteorological data

• Input item 2: Azimuth and tilt angles

• Input item 3: Mounting surface and array configuration

• Input item 4: Module specifications

• Input item 5: PCS specifications and capacity ratio

• Input item 6: String configuration

• Input item 7: Shading and surrounding obstacles

• Input item 8: Various loss conditions

• Common points where beginners are likely to get stuck when using PVSyst

• Considerations when using PVSyst results in practice

• Summary: It is important to use PVSyst with consistent input assumptions

What is PVSyst software used to verify?

PVSyst is simulation software for entering the design parameters of solar photovoltaic power systems and checking estimated energy production and the breakdown of losses. It is used not merely to calculate annual energy production but to assess the validity of a design proposal while organizing multiple factors that affect energy production, such as solar irradiance, temperature, tilt angle, equipment configuration, shading, wiring, and PCS conversion efficiency.

In planning a solar power plant, even if the local irradiance conditions are good, the actual power generation can vary depending on installation angle, shading, PCS capacity, wiring distance, temperature conditions, and other factors. Therefore, judging expected generation solely by module capacity can result in discrepancies between planned values and operational performance. In PVSyst, by entering these conditions and running simulations over the year, it becomes easier to identify which factors are likely to lead to reduced power generation.

In practical work, there are four main situations in which PVSyst is used: initial assessment, detailed design, stakeholder briefings, and energy production evaluation. In the initial assessment, it is used to check the estimated energy production for candidate sites and the differences caused by installation orientation. In detailed design, it is used to specify module count, PCS capacity, string configuration, shading conditions, and so on, and to verify whether the proposal can stand as a design. In stakeholder briefings, it shows the assumptions behind the energy production and the breakdown of losses, explaining why the projected energy production is what it is. For energy production evaluation after the start of operation, it can be used as a reference value for comparison with actual performance.

However, PVSyst does not automatically produce the correct answer simply by entering inputs. If the basis for the input values is weak, the reliability of the output results will also decrease. For example, if the meteorological data region is offset from the actual site, the azimuth orientation is mistaken, the shading conditions are oversimplified, or the PCS or module specifications differ from the actual equipment, you cannot use the simulation results as-is as a basis for decision-making.

What beginners should understand first is that PVSyst is not a "tool for predicting energy production" but a "tool for organizing energy production and losses based on the design conditions entered." What matters is not the operation of the software itself, but how closely the input conditions can be made to reflect actual site conditions. To use PVSyst in practice, you need to understand the meaning of each input item and configure them while cross-checking with drawings, equipment specifications, survey data, site photos, solar irradiation conditions, and so on.

Input Item 1: Location Information and Meteorological Data

The input items that tend to cause confusion in PVSyst at first are the site information and the meteorological data. Site information refers to the latitude, longitude, altitude, and regional conditions of the location where the power plant will be installed. Meteorological data refers to external environmental data that form the basis for power generation calculations, such as solar irradiance, air temperature, and wind speed. In PVSyst, projects are studied by comparing multiple design options based on the project's regional conditions and meteorological data.

One point beginners should be especially careful about is that selecting meteorological data from a nearby area does not necessarily adequately reflect the actual site conditions. In photovoltaic power generation, annual solar irradiance, temperature, snowfall, sea breeze, mountain shading, fog, and the local tendency for cloud formation all affect power output. Even within the same municipality, weather patterns can differ between the mountain side, the seaside, basins, and plateaus. When using meteorological data from locations distant from the site, you need to be aware of how those differences may affect the results.

Items to check in meteorological data include global horizontal irradiance, diffuse irradiance, ambient temperature, and wind speed. These relate to calculations of the irradiance reaching the module surface and of temperature-related losses. Don’t judge based only on irradiance; in high-temperature regions you should also consider output decreases caused by temperature rise. Wind speed can affect estimates of module temperature depending on installation conditions, so it’s advisable to check the contents of the meteorological data you use.

In practice, when entering location information, it is important to verify not only the address but also site drawings and coordinate data. Even if latitude and longitude are slightly offset, that may not make a significant difference on flat ground, but in mountainous areas or places with many surrounding obstacles it can affect shadow conditions around sunrise and sunset. Elevation can also be related to temperature conditions. When the position is clearly defined by on-site surveys or planning drawings, enter the information based on those sources whenever possible.

A common mistake beginners make is proceeding with the initial settings or the settings from past projects. Just because you can move through the simulation screens doesn't mean the site information or meteorological data are appropriate. In particular, if you reuse settings from previous projects even though the site differs for each project, you may calculate energy production without reflecting regional differences. When using PVSyst, it's important to first confirm "which location this meteorological data represents," "whether the distance and terrain differences to the site are acceptable," and "whether you can present it as justification when explaining the design."

Input Item 2: Azimuth Angle and Tilt Angle

In PVSyst, the azimuth and tilt angles are often a source of confusion. The azimuth angle indicates which direction the module surface faces. The tilt angle indicates how much the module surface is inclined relative to the horizontal plane. These two are important input parameters that determine the amount of solar radiation incident on the module surface.

In solar power generation, the amount of solar radiation a module receives changes depending on which direction the module surface faces relative to the movement of the sun. Generally, when prioritizing annual power generation, the installation angle is considered by taking the local solar altitude and azimuth into account. However, in actual projects there are constraints such as roof shape, site shape, site development plans, racking layout, adjacent property boundaries, maintenance access routes, snow accumulation, and wind loads, so the angle cannot be decided based on power generation alone.

One thing that often confuses beginners is the reference for azimuth angles. On drawings, angles are often indicated with north as the reference, while in software, if you do not understand the azimuth reference and the sign convention, you can easily mistake east and west directions. If a value entered intending to indicate a south-facing orientation is actually treated as the opposite or a different direction, the resulting energy production can change significantly. Before entering the azimuth, be sure to check the north direction on the drawing, the on-site orientation, and the angle definition used in PVSyst.

The approach to tilt angle also differs between rooftop and ground-mounted installations. For rooftop installations, the tilt is often matched to the existing roof pitch, so it may not be possible to change the tilt freely. For ground-mounted installations, you can choose the racking angle to some extent, but you need to balance row spacing, shading, wind, constructability, and maintainability. Increasing the tilt angle can be advantageous for solar gain in winter, but it can increase inter-row shading or raise the racking height. Conversely, reducing the tilt angle makes it easier to suppress inter-row shading, but requires consideration of soiling, snow accumulation, and drainage.

PVSyst allows you to compare multiple options by changing the azimuth and tilt angles. For beginners, rather than locking in a single set of conditions from the start, it is easier to understand if you compare several angles within the range possible in the design and evaluate energy production, shading, the number of modules that can be installed, and construction conditions comprehensively. However, when making comparisons, it is important not to change conditions other than the angles indiscriminately. If you change the weather data, modules, PCS, and loss conditions at the same time, it becomes difficult to identify the cause of differences in energy production.

In practice, it is also important to keep a record of the basis for entering the azimuth and tilt angles. If you record which information you used for the inputs—drawing number, design revision, on-site measurements, racking specifications, roof pitch, etc.—it will be easier to explain the power generation results later. When you are not yet familiar with operating PVSyst, after entering the angles you should check the on-screen display and the values in the report and always confirm that the calculations are being performed for the intended orientation and tilt.

Please translate the following input into English.

Input Item 3: Installation Surface and Array Configuration

Installation surfaces and array configuration are also input items that PVSyst beginners often find confusing. An installation surface is the surface on which modules are placed. Examples include roof surfaces, rows of ground-mounted racks, and installation areas divided into multiple orientations. Array configuration is the design-level classification of how multiple modules are grouped and which PCS or input circuit they are connected to.

For small, simple systems with a single south-facing surface, the way to think about the installation surface is relatively straightforward. However, in practice there are projects with east-west orientations, multiple roof surfaces, staggered roof levels, layouts that follow the terrain, sloping sites, and a mix of different mounting angles. In such cases, treating everything as a single surface can lead to discrepancies with the actual power generation characteristics.

For example, if east- and west-facing modules are treated under the same conditions, differences in generation patterns between morning and evening will not be reflected. Similarly, if areas with different tilt angles are treated as the same installation surface, differences in the irradiance incident on the module surface become difficult to discern. When multiple surfaces exist for design reasons, you must organize and enter each azimuth, tilt angle, number of modules, and connection destination.

What beginners often struggle with is how finely they should subdivide. The more you subdivide, the easier it is to reflect reality, but the number of input items increases and management becomes more complex. Conversely, if you aggregate too much, you cannot capture differences at the site. A practical guideline is whether the differences affect power generation, shading, PCS input, or string configuration. If the azimuth differs significantly, the tilt angle is different, shading conditions vary, the connected PCS is different, or the module types differ, consider treating them separately.

In array configuration, the relationship between module capacity and PCS capacity, the number of input circuits, the number of strings, and the arrangement of connections per mounting surface are important. If the actual wiring plan differs from the configuration used in the simulation, it may look fine in PVSyst but be infeasible in on-site design. In particular, when connecting multiple surfaces to a single PCS or when combining surfaces with different solar irradiance conditions into the same input circuit, differences in generation characteristics can have an impact.

In practice, before entering the installation surface and array configuration, it's smoother to have the single-line diagram, layout drawing, equipment list, and string table prepared. In the early stage, when detailed drawings are not yet available, enter them as assumed conditions on the premise that they will be updated later to match the detailed design. If you use only the results without recording that they are assumptions, misunderstandings may arise in later stages. When using PVSyst results as the basis for design, it is important to clarify which revision of the drawings the installation surface and array configuration are based on.

Input Item 4: Module Specifications

Module specifications are important input items that directly affect PVSyst simulation results. A module is a power-generating panel that converts sunlight into electricity. In PVSyst, energy production and electrical behavior are calculated based on module capacity, voltage, current, temperature characteristics, output characteristics, and other factors.

What beginners should first check is whether the module specifications they have entered match the specifications that will actually be adopted. Using a different specification just because the capacity is similar can cause simulation results to deviate. Modules differ not only in rated output but also in open-circuit voltage, short-circuit current, maximum power operating voltage, maximum power operating current, temperature coefficients, and so on. These values also affect the voltage range verification with the PCS and the string configuration.

Particular attention should be paid to the temperature coefficient. Solar modules generally see their output decrease as module temperature rises. In regions with high ambient temperatures or in roof-mounted conditions with poor ventilation, temperature-related losses can be significant. If module specifications are not entered correctly, the reduction in power generation due to temperature increases may not be reflected accurately.

Also, when assuming conditions that differ from the usual single-sided reception, such as with bifacial modules, you need to carefully verify the configuration method and the basis for your inputs. The results will vary depending on how much reflected light you expect, how you set the ground surface reflectance conditions, and how you treat the mounting structure and ground conditions. For beginners, rather than overestimating special conditions, it is safer to first create a stable simulation under basic conditions and then compare additional conditions afterward.

A common mistake when entering module specifications is using an outdated datasheet. Even modules that appear to share the same series name may differ in model number, output, cell configuration, and electrical characteristics. Specifications can change during planning, estimating, ordering, or installation. If you use a report without confirming that the specifications entered into PVSyst match the final selected product, assumptions among stakeholders can become misaligned.

In practice, verify the module datasheet’s revision, model, rated output, and key electrical characteristics, and cross-check them against the input values in PVSyst. Even when selecting existing data, do not rely solely on the model name; it is important to confirm that the main values match. When necessary, retain the supporting documents for the equipment specifications used in the project, as this makes later explanations easier.

Please translate the following input into English.

Input item 5: PCS specifications and capacity ratio

PCS specifications are also input items that can be confusing in PVSyst. A PCS is a device that converts the direct current power from solar modules into alternating current and delivers it to the grid or facility-side equipment. In PVSyst screens and documentation it is sometimes treated as an inverter. Here, we will refer to it as PCS to match the terminology commonly used in Japanese practice.

Beginners should pay attention to the relationship between module capacity and PCS capacity. In solar power generation systems, the total capacity of the modules may be designed to exceed the PCS capacity. This is because modules do not always generate at their rated output, and such a design is considered from the perspectives of annual energy production and equipment utilization. However, the larger the capacity ratio, the more likely it is that the PCS will limit output during periods of strong solar irradiance.

PVSyst simulates including such output limits and conversion efficiencies. Therefore, if you input a PCS capacity larger than the actual one, limitation losses may appear smaller. Conversely, if you input it smaller, limitation losses may appear larger. It is important to correctly organize the planned PCS capacity, the number of input circuits, and the capacity of the modules to be connected.

Another point that causes confusion with PCS specifications is the input voltage range. A module string's voltage changes with temperature. The voltage rises at low temperatures and falls at high temperatures. Therefore, when determining the number of modules in a string, check that the maximum voltage at low temperature does not exceed the PCS's allowable range and that the operating voltage at high temperature falls within the appropriate range. Even if the configuration is valid in PVSyst, ignoring the site's minimum temperature or the equipment specifications can cause problems in detailed design.

Conversion efficiency is also important. The PCS converts the input DC power to AC, but losses occur in the process. Efficiency can vary depending on output conditions and is not necessarily the same at low and high loads. If the PCS specifications entered into PVSyst differ from the actual equipment characteristics, the annual energy production forecast will be affected.

In practice, when entering PCS specifications you check not only the rated capacity but also the input voltage range, maximum input current, number of input circuits, conversion efficiency, and ambient temperature conditions. Also, when using multiple PCS units, you need to organize which mounting surfaces and strings are connected to which PCS. When explaining PVSyst results, presenting the module capacity, PCS capacity, capacity ratio, and curtailment losses together makes it easier for stakeholders to understand.

Input Item 6: String Configuration

String configuration is the design parameter that determines how to create a unit composed of multiple modules connected in series. For PVSyst beginners, entering the number of modules and the PCS capacity may seem sufficient, but in reality the string configuration affects voltage, current, power generation characteristics, and shading effects.

When deciding the number of modules in a string, check the PCS input voltage range and the electrical characteristics of the modules. The more modules connected in series, the higher the string voltage. Because voltage rises at low temperatures, you must ensure the maximum voltage does not exceed the allowable range. Conversely, because voltage falls at high temperatures, also verify that the operating voltage does not become too low. If you neglect these checks, even if the number of modules is correct in the design, problems may arise in the actual operating range.

In PVSyst, there is a concept of organizing combinations of modules, strings, and PCS for each sub-array. Beginners should not adopt the configuration proposals shown by the software as-is; they need to verify that these match the actual wiring, equipment specifications, and construction conditions. If the simulated configuration does not match the single-line diagram or the string table, the energy production results will be difficult to use as a design justification.

In places with shading, the impact of string configuration becomes even greater. Including modules that are partially shaded in the same string can affect the power generation of the entire string. The effect of shading is not determined solely by the shaded area; it also varies with module connections, circuit configuration, and the timing of the shading. When considering near-field shading, you must pay attention not only to the shape of the shadow but also to the electrical grouping of the connections.

A common mistake beginners make is matching only the total number of modules without thoroughly checking the number of modules per string and their connection points. Even with the same total number, if the modules per string or the number of parallel strings change, the PCS input conditions and the wiring conditions will change. Also, due to site layout constraints, when leftover modules are placed in a different row, the assumed string configuration can differ from the actual layout.

In practice, before entering data into PVSyst it is important to cross-check the layout plan with the string table. Verify which modules in which columns belong to the same string, which PCS input they connect to, and that they are not mixed into the same circuit as areas prone to shading. At the stage before detailed design you may run simulations using a provisional string configuration, but in that case you must clearly mark it as a "provisional configuration".

Input Item 7: Shadows and Surrounding Obstacles

Shading input is an item that PVSyst beginners particularly tend to find confusing. In solar power generation, shading has a large impact on energy production. Surrounding buildings, trees, mountains, utility poles, rows of mounting racks, roof level differences, and equipment can all cause shading. In PVSyst, it is necessary to consider distant shading and nearby shading separately.

Far-field shading refers to shadows from mountain ranges or distant buildings that affect whether the sun is visible from the entire solar power plant. In PVSyst, there is an approach that treats far-field shading as the horizon. In mountainous or valley terrain, morning and evening solar irradiance can be obstructed, so inputting far-field shading is important. Even for flatland projects, it is advisable to check for large surrounding terrain features or buildings.

Nearby shading refers to shadows cast on part of a module or on specific rows by objects located around or within the power plant site. Examples include adjacent buildings, fences, trees, HVAC equipment, roof protrusions, and shadows between racking rows. Nearby shading changes position depending on the time of day and season, affecting energy yield as partial shading. In PVSyst, there is an approach of creating and evaluating a three-dimensional scene to assess nearby shading.

One common mistake beginners make when entering shadows is judging based only on on-site photos. Even if there are few shadows on the day you visit, shadows can stretch long in winter or during the morning and evening. Conversely, even if an obstruction appears prominent in a site photo, its impact on generation hours may be limited depending on the sun’s path. Shadows need to be checked not just by the impression from photos but based on position, height, distance, solar altitude, and azimuth.

Also, care must be taken in how trees are handled. Trees change their amount of foliage with the seasons, and their height and crown spread change as they grow. Even if the issue appears minor at the planning stage, shadows may increase after several years. If felling or pruning is assumed, you must confirm that such management will be maintained. Even when shadows are not included in PVSyst, it is necessary to make clear in practical documentation that the assumption is either "no shading considered" or "shading simplified."

Shading between racking rows is also important. For ground-mounted installations, the front row of racks can cast shadows on the rear rows. Conditions such as increasing the tilt angle, narrowing row spacing, or changes in land elevation can increase inter-row shading. If you cram in modules solely to maximize generation capacity, shading losses will increase and the actual power output may fall short of expectations.

In practice, as documentation supporting shadow inputs it is useful to organize the site survey of existing conditions, heights of surrounding buildings, tree locations, topography, layout drawings, and site photographs. When explaining energy production to stakeholders, it is important to be able to explain how far shadows were modeled and what was simplified. PVSyst’s shadow settings are not intended for visual fine‑tuning, but to appropriately reflect the factors that affect energy production.

Input Item 8: Various Loss Conditions

What beginners often get confused about at the end in PVSyst are the various loss conditions. Loss conditions are the reduction factors considered to bring ideal energy production closer to actual energy production. In solar power generation, various losses occur, such as temperature, soiling, wiring resistance, mismatch, shading, PCS conversion, AC-side wiring, and equipment downtime.

What is important when setting loss conditions is that it is neither correct to estimate everything conservatively nor to make everything look small. In practice, you need to set values that can be justified based on site conditions, equipment specifications, construction quality, maintenance plans, and past similar projects. If losses are set unrealistically low without justification, the estimated power generation may appear overstated. Conversely, if you err too far on the safe side and set losses too high, the evaluation of the design proposal may appear lower than the actual situation.

Temperature losses are reductions in output caused by an increase in module temperature. Temperature losses can be larger in regions with high ambient temperatures, on rooftops with poor ventilation, or in installations where heat tends to accumulate on the back of the modules. When inputting data, consider meteorological data, installation type, rack height, and ventilation conditions. Rather than simply using standard values, verify that they are reasonable given the site conditions.

Soiling loss refers to the reduction in solar radiation caused by sand and dust, pollen, bird droppings, fallen leaves, soiling after snowfall, deposits from the surrounding environment, and similar factors. The tendency to accumulate soiling can differ around factories, farmlands, coastlines, mountainous areas, and along roads with heavy traffic. Whether regular cleaning is carried out or maintenance is left to natural rainfall also changes how this should be considered. If soiling loss is set low without a cleaning plan, it may not match actual operational conditions.

Wiring losses are losses caused by the wiring resistance on the DC side and the AC side. Losses increase with longer cable lengths, higher currents, or smaller conductor cross-sectional areas. During the initial study phase the detailed wiring routes may be undecided, but in the detailed design phase it is desirable to approach the actual cable lengths and conductor cross-sectional areas. Treating wiring losses casually affects not only the power generation but also explanations of voltage drop and equipment planning.

Mismatch loss is the loss that occurs when outputs within the same circuit do not match due to differences in individual module characteristics, levels of soiling, shading, aging, and other factors. Since not all modules generate power under exactly the same conditions, it is necessary to allow for a certain amount of loss. In particular, caution is required when combining modules with differing orientations, tilts, or shading conditions in the same circuit.

A common mistake beginners make with loss conditions is reusing the values from the previous project unchanged. Loss conditions vary depending on the project's location, installation method, equipment configuration, and operational policy. Referring to values from past projects can be useful, but you should not use them without confirming they are appropriate for the current site. Because PVSyst reports show the breakdown of losses, it is important to review which losses are large and whether any configured values look unreasonable.

Common Points Where Beginners Get Stuck in PVSyst

A common reason beginners in PVSyst get stuck is less about the operation itself and more about proceeding without understanding the meaning of the input values. Even if no error appears on the screen, the design may still be inappropriate. Because there are many input fields, it’s tempting to enter default values or values from past projects to complete the simulation, but you need to be careful if you plan to use those results for stakeholder explanations or design decisions.

The first thing I want to confirm is version control of the input conditions. In solar power plant planning, the layout drawings, single-line wiring diagrams, equipment specifications, site development plans, and interconnection conditions may change during the process. If you don't know which set of design conditions the PVSyst simulation was created from, reviewing the results later will be confusing. In particular, if the number of modules, the number of PCS units, the tilt angle, or the shading conditions change, the power generation results may also change.

The next thing to confirm is the distinction between assumed conditions and confirmed conditions. In preliminary assessments, meteorological data, loss conditions, wiring distances, and equipment specifications may be provisional. Calculating based on assumptions is not a problem in itself, but treating those results as definitive values can lead to misunderstandings. When submitting PVSyst results, you need to clarify which conditions are confirmed and which are assumed.

Also, checking units is important. PVSyst handles many numerical values such as angles, distances, areas, capacities, voltages, currents, and temperatures. If you overlook the units in input fields, you may enter values that are off by an order of magnitude. Confusing the units for capacity, cable length, loss rates, or temperature conditions can greatly affect the results. Beginners should make a habit of reconfirming the key values in the report and overview screens after entering data.

Also, care is needed when interpreting simulation results. Looking only at annual energy production can make it difficult to detect design issues. By checking monthly energy production, loss diagrams, performance ratio, shading losses, temperature losses, output curtailment, wiring losses, and so on, you can identify where the major causes of reduced output lie. When reading the results, check not only the energy production figures but also whether the breakdown of losses is consistent with the input conditions.

For beginners, what matters is not whether the "simulation has completed" but whether the "results are consistent with the design conditions." Even if the annual energy output appears high, it cannot be considered reliable if shading was not included, wiring losses were set too low, PCS capacity differs from the actual, or module specifications are incorrect. Conversely, if the energy output appears low, it may be caused by input errors or excessively large loss settings.

Considerations When Using PVSyst Results in Practice

When using PVSyst results in practice, it is important not to extract only the numbers but to treat them together with the underlying assumptions. Annual energy production, performance ratio, and the breakdown of losses all depend on the input conditions. Therefore, if you communicate only the production figures to stakeholders, you may later be unable to explain "why those numbers were obtained."

A practical way to organize work is to clarify the purpose of the simulation. If the purpose is an initial study, the focus will be on comparing candidate sites and layout options. If the purpose is detailed design, the focus will be on specifying equipment configuration and loss conditions to determine whether it constitutes a viable design proposal. If the purpose is to explain to stakeholders, it is important to clearly present the assumptions for power generation and the breakdown of losses. Different purposes require different levels of accuracy and depth of explanation.

In addition, the results from PVSyst are not definitive on their own. They must be assessed in combination with on-site surveys, design drawings, equipment specifications, construction conditions, maintenance plans, and grid-connection conditions. Even if a layout shows a high energy yield in PVSyst, it may be difficult to adopt in practice if there are issues such as poor on-site constructability, insufficient maintenance access, interference with drainage planning, or difficulty managing shading.

When explaining to stakeholders, it is easier to convey the information if you concisely organize the main input assumptions as well as the generation figures. Explain site information, meteorological data, module capacity, PCS capacity, azimuth, tilt angle, treatment of shading, and main loss conditions together so the assumptions behind the results are clear. In particular, whether shading was taken into account and how soiling and wiring losses were estimated are parts that are likely to be questioned later.

When using PVSyst results for comparisons, it's important to make the comparison conditions consistent. For example, if you compare Option A and Option B and Option A has shading modeled in detail while Option B uses simplified shading, you won't be able to tell whether the difference in energy production is due to layout differences or differences in input precision. When comparing, as a basic rule align meteorological data, loss conditions, equipment specifications, evaluation period, etc. as much as possible, and change only the items you want to examine.

When comparing actual generation after the start of operation, you should not use PVSyst’s results directly to judge performance; instead, it is necessary to take into account actual meteorological conditions, downtime, power curtailment, and maintenance status. Simulations are projections based on specific weather and design conditions and will differ from actual weather and operational conditions. In performance comparisons, it is important to check together differences in solar irradiance, shutdown history, equipment faults, soiling, and changes in shading.

To become proficient in using PVSyst in practice, it is important not only to learn how to operate the software but also to establish a workflow for input, verification, explanation, and updating. As a project progresses the design conditions change, so instead of continuing to use old simulation results, update them when significant changes occur. In particular, confirm the need for re-simulation when there are equipment changes, layout changes, PCS capacity changes, shading condition changes, or changes to loss conditions.

Summary: When using PVSyst, it's important to use consistent input assumptions

PVSyst is simulation software used to check the energy production and losses of solar power generation systems and to evaluate the validity of design conditions. For beginners, it has many input fields, and it can be easy to be unsure which values to enter and on what basis. However, if you grasp the basic concepts, PVSyst becomes a tool that helps organize generation forecasts and supports design decisions and explanations to stakeholders.

Particularly important are eight items: site information and weather data, azimuth and tilt angles, mounting surface and array configuration, module specifications, PCS specifications, string configuration, shading, and various loss conditions. These may appear to be independent of one another, but in reality they are closely related. Changing the installation angle alters shading and power generation; changing the string configuration affects compatibility with the PCS and the impact of shading. If you change the loss conditions, the estimated annual energy output can change even for the same installed capacity.

When using PVSyst, it is important to first align the basis for the input values. Check site conditions, drawings, survey data, equipment specifications, shading information, wiring conditions, and maintenance policies, and record which information was used as the basis for the inputs. Next, do not judge simulation results based only on annual energy production; check monthly energy production and the breakdown of losses. Finally, when presenting results to stakeholders, explain not only the numbers but also the underlying assumptions.

To avoid mistakes in PVSyst as a beginner, rather than aiming for perfect operation from the start, a quicker approach is to understand the meaning of each input item and work through the points to be checked one by one. When using assumed conditions, make it clear that they are assumptions and update the conditions as the design progresses. Even when reusing settings from past projects, always review whether they are appropriate for the specific site.

In designing a solar power plant, it is necessary to make comprehensive judgments not only based on energy yield simulations but also taking into account site topography, shading, constructability, and maintainability. To use PVSyst results in a manner closer to practical application, accurately acquiring site information and reflecting it in the design conditions is indispensable. By linking and managing simulations, on-site surveys, design verification, and records before and after construction, it becomes easier to explain later the basis for the inputs and the resulting decisions.