Basic Operations of PVSyst | 5 Steps to Check Power Generation

In the design, proposal, and pre-construction review of a solar power plant, how to verify the annual energy production is an important consideration. PVsyst is known as software used for studying solar power systems, for sizing, and for simulating energy production. However, for first-time users, the many screen items and input parameters can make it difficult to know where to start.

Note that the product’s commonly official spelling is PVsyst. In this article, to match search usage, headings use the spelling PVSyst. Because the names of the screens and menu items you actually operate may vary depending on the software version and your environment, this article focuses on the basic concepts for checking energy output rather than on detailed procedures for specific screens.

This article explains, for practitioners searching for "How to use PVSyst", the basic workflow up to confirming energy production, divided into five steps. Rather than delving into detailed design theory, it first organizes the input order, key checkpoints, and how to interpret results that often confuse practitioners, and summarizes ways of thinking to apply simulation results to on-site work and design decisions.

Table of Contents

• Basics to keep in mind before checking energy production in PVSyst

• Step 1: Organize project conditions and the installation site

• Step 2: Check meteorological conditions and solar radiation data

• Step 3: Input the basic conditions of the power generation equipment

• Step 4: Review loss conditions and run the simulation

• Step 5: Read the annual energy production and monthly energy production

• Points to note when using PVSyst results in practice

• Approach to linking energy production verification to site management

• Summary: Consider PVSyst basic operations by separating input conditions and result verification

Basics to Understand Before Checking Energy Production in PVSyst

When learning the basic operations of PVSyst, the most important thing at the outset is to view the software not merely as a tool for calculating energy output, but as a tool for organizing design conditions and for checking, step by step, the factors that affect energy output. If you try to get the energy output numbers quickly, you are likely to overlook the meaning of the input conditions, and later find it difficult to explain "why the energy output turned out that way."

The energy output of a solar power plant varies depending on multiple conditions: the site's solar irradiance, temperature, azimuth, tilt angle, system capacity, equipment specifications, shading effects, wiring losses, soiling, performance changes with age, operating conditions, and so on. In PVSyst you set the parameters related to these factors and then check the resulting annual energy production, monthly generation, and breakdown of losses. In other words, the purpose of using it is not only to "calculate energy production" but to "understand which conditions influence that production."

In practice, simulation results are used for design reviews, internal briefings, customer presentations, construction planning, and profitability assessments of power generation projects. Therefore, operators should not accept the numbers at face value; they must verify whether the assumptions are reasonable, whether there are input errors, and whether the results conflict with on-site conditions. In particular, installation location, orientation, tilt angle, system capacity, and shading conditions are items that are likely to affect power output.

Also, the PVSyst screens contain many technical terms, but you do not need to memorize them all at the initial stage. First, it is important to grasp the overall workflow: set the project conditions, check the meteorological data, enter the equipment/system conditions, review the loss conditions, and view the results report. Once you understand this flow, it becomes easier to organize the meanings of the finer items later.

Many people who search for "how to use PVSyst" want to check the energy output but are unsure which conditions to organize first and which parts of the results to look at. Therefore, in practice, rather than aiming for advanced analysis from the outset, it is more helpful as a basic workflow to clearly separate organizing information before input and the checkpoints for verifying results after output.

Step 1: Clarify project requirements and the installation site

The first step in verifying power generation is to organize the project parameters and the installation site. When you begin a new study in PVSyst, clarify the location of the power plant in question, the type of system, the study objectives, and the installation conditions. If you proceed while these elements remain ambiguous, discrepancies may arise later in the meteorological and equipment conditions, making the simulation results difficult to explain.

The first thing to confirm is where the power plant will be installed. The electricity output of a solar power plant is influenced by regional solar irradiance and temperature. Even with the same installed capacity, annual generation will vary if irradiance conditions differ. Therefore, the latitude, longitude, elevation, and surrounding environment of the installation site serve as the basic conditions for simulation. In practice, preparing as accurate location information as possible—not just the project name or address—makes it easier to verify later stages.

Next, organize the types of systems under consideration. Whether it is ground-mounted, roof-mounted, on sloped terrain, or on flat ground will change the conditions and precautions that need to be entered. For ground-mounted systems, the orientation of the mounting structure, row spacing, and the impact of surrounding shading are important. For roof-mounted systems, the azimuth and tilt angle of the roof surface, the available area, and the presence of obstructions are important. Before checking the power generation, you need to clarify which installation type you are assuming.

When organizing project conditions, keep the project stage in mind. The required level of input accuracy varies depending on whether you want to grasp an estimated power generation in an initial review or to verify details under conditions close to the design. In the early stage, you may capture trends with an approximate installed capacity and provisional loss assumptions. On the other hand, in stages close to detailed design or a proposal, you need to set equipment specifications, layout, shading, and loss conditions more carefully.

A common mistake when using PVSyst is filling in the on-screen fields in order and later losing track of the underlying assumptions. In practice, it helps to first prepare a project memo that organizes the installation location, the capacity under consideration, the assumed orientation and tilt angle, the meteorological conditions to be used, how shading will be handled, and the results you want to generate, so that checking the entered data becomes easier.

At this stage, it's more important to establish the basis for the calculations than to rush out power generation figures. If the project conditions are clearly defined, you can later explain, when reviewing the results, what installation conditions those generation figures were based on. In internal reviews and client explanations, conveying the assumptions along with the annual power generation, rather than simply presenting the annual generation, makes it easier to communicate the meaning of the numbers.

Flow 2: Check meteorological conditions and solar radiation data

After setting the project conditions, the next step is to check the meteorological conditions and solar irradiance data. In solar power generation simulations, meteorological data serve as the basis for generation calculations. Because solar irradiance in particular directly affects generation, it is important to confirm which location's data are being used and whether the data are appropriate for the installation site.

PVSyst uses meteorological data appropriate to the installation site to run simulations based on conditions such as solar radiation and ambient temperature. Because the items and periods included differ depending on the type of data used, choosing a meteorological dataset is not the end; it is important to confirm that the data match the target site. Using data from a location distant from the planned installation can result in discrepancies with the actual environment. In mountainous areas, coastal areas, snowy regions, and basins, trends in solar radiation and temperature can differ even over short distances.

When checking meteorological conditions, it is useful for practical work to look not only at the annual solar radiation but also at monthly trends. Even if the annual power generation is similar, the seasonal distribution of generation can differ. Some regions tend to see higher generation in summer, while others may not increase as expected due to efficiency losses from higher temperatures and the influence of weather. In winter, generation can be affected by reduced solar radiation, lower solar altitude, and the effects of snow cover or overcast skies.

If the purpose of checking power generation is to assess the financial balance, it is important not only to look at the annual total but also to understand how generation varies month by month. In planning for selling power or for self-consumption, seasonal differences in generation affect operational plans. From a design and construction standpoint as well, for months with low generation it is necessary to distinguish whether the cause was sunlight/irradiance conditions or shading and equipment-related issues.

Temperature conditions must not be overlooked. For photovoltaic systems, higher irradiance does not necessarily result in a simple increase in power generation. In high-temperature environments, rising module temperatures can lead to reduced output. PVSyst accounts for not only irradiance but also temperature-related conditions in its calculations, so the validity of the meteorological data affects the results.

When checking meteorological data, pay attention to the period and nature of the selected data. Whether the data are close to a long-term average or to a specific year affects how the results should be interpreted. In practice, it is important not to treat simulation results as guarantees of future power generation, but rather as estimates based on the specified meteorological conditions.

The key point in this workflow is not to treat the meteorological conditions as mere initial settings to be skimmed over. Because much of the generation output depends on solar radiation, if the results later seem off, first check the meteorological data: the location, the solar irradiance, and the monthly trends. The less familiar you are with the input operations, the more carefully you should examine the meteorological conditions—this makes it easier to assess whether the generation output is reasonable.

Step 3: Enter the basic conditions of the power generation equipment

After checking the meteorological conditions, enter the basic parameters of the power generation system. Here you set the main conditions that affect energy output, such as system capacity, number of modules, circuit configuration, equipment specifications, orientation (azimuth), and tilt angle. This is the part of PVSyst's basic operation that requires the most practical verification.

First, what you should be aware of is the relationship between installed capacity and layout conditions. If the same region, the same orientation, and the same loss conditions apply, energy generation roughly correlates with installed capacity. However, it is not sufficient to simply increase capacity. You need to consider available installation area, racking layout, maintenance aisles, clearances, shading effects, and interconnection conditions. If the capacity used in simulations differs from the capacity that can actually be constructed, the results of generation assessments become difficult to use in practice.

Orientation and tilt angle are basic parameters that strongly influence energy production. In many projects in Japan, conditions close to south-facing tend to yield higher annual energy production, but the optimal orientation varies depending on site shape, roof shape, and the purpose of the installation. If self-consumption is prioritized, the time-of-day distribution of energy production should also be taken into account. When checking energy production in PVSyst, do not decide orientation and tilt angle based only on general rules; they should be matched to the installation conditions of the specific project.

When entering equipment specifications, confirm that the selected conditions match the design. The power generation system’s output characteristics, temperature characteristics, circuit configuration, and the combinations among devices affect power generation and loss calculations. If the specifications differ here, the accuracy of the results will be affected. In practice, it is advisable to enter data while cross-checking the figures against the design documents and equipment specification sheets.

Regarding circuit configuration, settings such as the number of series and parallel connections are important. If the connection conditions are not appropriate, warnings or inconsistencies may appear in the simulation. If a warning appears, do not ignore it; check whether the voltage range or input conditions have any problems. If you only look at the power output, you may overlook such design inconsistencies, so caution is necessary.

Also, when there are multiple installation surfaces, you need to consider the orientation and tilt angle of each separately. Treating east- and west-facing roof surfaces, multiple sections, and areas with different slopes under a single set of conditions can lead to discrepancies with actual generation trends. While simplification may be used in preliminary assessments, in detailed studies it is better to organize the conditions for each installation surface, which makes the results easier to explain.

After entering the equipment conditions, always review the overall consistency. Verify that the equipment capacity, number of modules, circuit configuration, azimuth, and tilt angle match the project documentation. In particular, misreading units, entering angles incorrectly, errors in the capacity's digit placement or order of magnitude, and confusing the installation surface are mistakes that commonly occur in practice. Even after becoming familiar with PVSyst operations, it is important not to omit the input verification procedures.

In this workflow, it is important not only to "input" the conditions of the power generation equipment but also to "verify that they match the actual design conditions." The reliability of simulation results is greatly influenced by the accuracy of the input conditions. Even if the generated power is higher or lower than expected, first checking whether there are errors in the equipment conditions makes it easier to isolate the cause.

Step 4: Review Loss Conditions and Run the Simulation

After entering the system conditions, review the loss conditions and run the simulation. In solar power generation simulations, the power calculated from ideal irradiance does not directly equal the final generated output. In practice, various factors are subtracted, such as temperature losses, shading losses, wiring losses, equipment conversion losses, soiling losses, and mismatch losses.

When checking energy production in PVSyst, the important thing is not to leave loss conditions at their initial or placeholder values but to verify that they match the project's conditions. Of course, that doesn't mean the tool is unusable until every loss has been measured in detail. In preliminary evaluations it is common to use general assumptions for a rough estimate. However, when using the results for proposals or design decisions, you must be able to explain which losses you expected and to what extent.

The effect of shading is an important factor affecting power generation. If there are surrounding buildings, trees, mountains, utility poles, or inter-row shading between equipment, failing to set shadows appropriately can lead to generation being estimated higher than it actually is. The impact of shading can be particularly noticeable during periods of low solar altitude and in winter. If there are obstacles around the site or on the roof, it is necessary to carefully determine whether shadows can be ignored.

Losses due to soiling also vary according to site conditions. The causes of soiling—wind-blown dust, pollen, bird fouling, nearby construction, agricultural land, coastal environments, and so on—differ from site to site. They are also affected by cleaning schedules and rainfall patterns. Setting overly optimistic assumptions can lead to an overestimation of energy production. Conversely, applying large loss values without justification can make the assessment results unduly conservative.

Wiring losses and equipment conversion losses should be checked based on the design conditions. Losses vary depending on cable length, current, voltage, equipment configuration, and so on. Provisional values may be used in preliminary studies, but in detailed studies it is desirable to reconcile them with drawings and system configuration. Especially in large-scale power plants, wiring distance and collection methods can affect power generation.

Losses related to temperature are also important. Solar PV systems can heat up when exposed to sunlight, which can lead to reduced output. Because heat dissipation conditions vary depending on the mounting method, the way temperature conditions are considered differs for roof-mounted, ground-mounted, and near-enclosed installations. PVSyst reflects temperature-related conditions in its calculations, so verification according to the mounting method is necessary.

After confirming the loss conditions, run the simulation. After running it, check not only the annual energy production figures but also any warnings, errors, and the breakdown of losses. If there are warnings, review whether the input conditions contain inconsistencies or whether the settings are realistic. Getting results does not mean the job is done; verifying that the simulation was executed under appropriate conditions is a basic practice in professional work.

At this stage, the important thing is not to treat loss conditions as "numbers for adjusting the power generation." Losses are items to reflect site conditions and design conditions. Rather than changing losses to bring the power generation closer to a desired figure, you need to adopt the stance of confirming the power generation as the result of entering well‑founded conditions.

Step 5: Read Annual and Monthly Power Generation

After running the simulation, check the annual energy production and the monthly energy production on the results screen and in the reports. In basic PVSyst operations, the figure most people ultimately want to see is how much energy will be generated annually. However, in practice you should not judge based only on the annual total; you need to verify monthly variations, the breakdown of losses, and the plausibility of the energy production.

Annual electricity generation is the central figure that indicates how much electrical energy the target power plant is estimated to produce in one year. In proposals and internal reviews, this number is often given significant weight. However, annual generation is ultimately a simulation result based on input conditions. If meteorological conditions, equipment conditions, or loss conditions change, the results will change. Therefore, when viewing annual generation, always confirm it together with the underlying assumptions.

Monthly power generation is useful for checking the plausibility of results. It is natural for generation to increase in seasons with high solar radiation and decrease in seasons with low solar radiation. However, if there is a concern—such as a single month being extremely low, seasonal trends not matching expectations, or generation being too high given the equipment conditions—this can be a cue to review the input conditions.

When reading power generation figures, it becomes easier to judge if you also check generation per unit of installed capacity. This is because simple annual generation alone makes it difficult to compare projects with different system sizes. By looking at generation per unit of installed capacity, you can more easily determine whether the level is reasonable for the region and installation conditions. However, this value also varies depending on weather conditions and loss conditions, so it is important not to judge superiority or inferiority based on it alone, but to view it together with the underlying assumptions.

In the results report, we also check the flow of losses. By examining where and to what extent losses occur from solar irradiance to power output, it becomes easier to identify the causes of reduced generation. Whether shading losses, temperature-related losses, or losses in wiring and equipment are most prominent will determine the direction of design improvements.

If shading losses are large, there may be room to review the layout, spacing, and how obstacles are handled. If temperature losses are large, check the installation method and ventilation conditions. If wiring losses are large, consider reviewing the cable plan and equipment layout. In this way, PVSyst results are not just numbers for energy production but can be used as clues for design improvement.

Also, when sharing reports internally or externally, it is important not to extract only the numerical values but to explain them together with the input conditions, meteorological conditions, equipment conditions, and loss conditions. Documents that do not make the basis for the power generation figures clear become difficult to use later when verification is required. Conversely, if the underlying assumptions are well organized, it is easier to explain differences in power generation and the effects of design changes.

What you should keep in mind in this workflow is to treat the result review as a "check your answers" step. For the conditions you entered, verify whether the energy production is within a reasonable range, whether the month-by-month trends show any anomalies, and whether the breakdown of losses aligns with the on-site conditions. In basic PVSyst operation, the task does not end with pressing the run button; interpreting the results is part of the overall process.

Points to note when using PVSyst results in practice

After checking the power generation in PVSyst, there are several points to note when using those results in practice. The most important is not to treat the simulation results as definitive values. Power generation is influenced by weather conditions and operational status, so it will not exactly match actual generation. It should be treated solely as an estimated result based on the assumptions you set.

Especially when using the results for customer briefings or internal approvals, it is important to clearly state the assumptions behind the results. If the installation location, meteorological data, system capacity, orientation, tilt angle, loss assumptions, or the way shading is handled change, the energy generation will also change. Presenting only the annual energy generation without showing these factors will make it difficult to explain later if the conditions change.

Also, attention must be paid to discrepancies between simulation conditions and construction conditions. Equipment that could be neatly arranged during the design phase may be altered during construction because of terrain, boundaries, structures, access routes, maintenance spaces, or surrounding obstacles. If the layout, tilt angles, or equipment capacity change, the power generation should be reconfirmed. Do not use the initial study results as the final values.

Checking for input errors is also important. PVSyst is software that performs specialized calculations, but if the input values are incorrect, the results will be incorrect as well. Choosing the wrong installation site, entering the wrong azimuth, incorrect tilt angle, an error in the order of magnitude of the capacity, mixing up equipment parameters, or incorrect loss settings (too high or too low) will affect power generation. If the results differ significantly from what was expected, it is standard practice to first review the input conditions before questioning the calculation method.

In practice, you may compare multiple conditions: changing the tilt angle, changing the equipment capacity, changing the layout, or whether or not shadow effects are considered. In such cases, use clear names for the conditions and make it explicit which result corresponds to which condition. As similar files or conditions accumulate, you may accidentally use old results or intermediate findings.

Care must also be taken in handling reports. PVSyst reports contain a great deal of information, but the information required varies depending on the reader. For design personnel, the breakdown of losses and equipment conditions are important, while for business planners the annual energy production and monthly generation may be more important. When using the report as material, it is important to organize and present the necessary information according to what the recipient wants to assess.

Furthermore, power generation simulations are not something that can be completed in isolation. They are linked to site surveys, surveying, design, construction planning, and maintenance planning. If there are steps, slopes, or obstacles on site, desk-based conditions alone are not sufficient to make an adequate assessment. To make effective use of simulation results, it is necessary to accurately grasp site conditions and update the assumptions as needed.

Thus, when using PVSyst results in practice, not only numerical accuracy but also transparency of assumptions, verification of inputs, consistency with site conditions, and clarity as documentation are important. After learning the basic operations to check energy production, being mindful of how to evaluate the results and how to explain them will make the simulation usable in practice.

Approach to Linking Power Generation Verification to On-site Management

Verifying energy production in PVSyst is not something that can be completed solely within the design room or office. To make the simulation results useful for actual solar power plant construction, coordination with site conditions is indispensable. No matter how favorable the design’s projected energy production appears, if the local terrain, orientation, slope, obstacles, construction accuracy, and maintainability are not aligned, it will be difficult to achieve the expected operation.

Even if equipment is arranged at a fixed azimuth and tilt angle in simulations, actual on-site layouts can change due to differences in ground elevation and boundary conditions. If the height or angle of the mounting structure is altered to follow the terrain, the way shadows fall and the power output may also be affected. Therefore, to make the results of power output verification useful on site, it is important to match the design conditions and the actual conditions as closely as possible.

Also, at solar power plants, the accuracy of pile positions and racking layout affects energy yield and maintainability. If placement deviations are large, they can influence inter-row spacing, aisle widths, and shading conditions. To reproduce the layout conditions assumed in PVSyst on site, accurate surveying and position control are required. Rather than treating energy yield simulation and field construction separately, it is important to ensure the design conditions are correctly linked to the site.

Even when you use power generation verification results to improve a design, site information remains important. If shadow losses are a concern, check the influence of nearby obstacles and the terrain. If you want to increase equipment capacity, verify the actual area available for layout and the maintenance access routes. If you want to adjust the tilt angle or orientation, confirm racking conditions and constructability. Even if you identify improvements from simulation results, you must confirm whether they can be implemented on site.

Even after operations begin, monitoring power generation remains important. By comparing simulation results with actual values, you can confirm whether the plant is operating close to expected conditions. However, actual values are affected by weather, temporary outages, soiling, and equipment condition. Therefore, rather than simply comparing simulated and actual values, it is necessary to consider the time period, weather conditions, outage history, and maintenance status together.

From a site management perspective, it is important to link confirmation of expected power output at the design stage, location management during construction, and verification of actual performance during operation. If these are fragmented, it becomes difficult to notice problems such as simulations showing good results while the on-site layout has been changed, or unexplained declines in power generation after operations begin.

PVSyst is an effective tool for assessing power generation, but to apply its results on-site it is necessary to accurately capture local site information and have a system to manage design and construction conditions. In particular, having an environment where pile locations, panel layouts, terrain information, and construction progress at a solar power plant can be verified on-site makes it easier to link simulation results with actual construction.

The verification of power generation should not be treated as mere desk calculation; it is important to consider it as part of the overall quality management of the power plant. Prepare the input conditions, interpret the results, cross-check them with on-site conditions, and, where necessary, reflect them in the design and construction. By establishing this workflow, the basic operation of PVSyst gains greater practical value.

Summary: Consider PVSyst's basic operations by separating input conditions from result verification

The basic procedure for checking energy production in PVSyst is easier to understand if you think of it as five steps: organizing project conditions, verifying meteorological conditions, entering equipment parameters, reviewing loss parameters, and interpreting the results. Even if the interface appears to contain many items, separating and organizing the tasks by purpose makes it clear where and what to check.

The first thing to do is to clarify the installation site and the objectives of the study. Next, confirm the meteorological conditions appropriate to the target site and grasp the trends in solar irradiance and temperature. Based on that, input the basic conditions such as system capacity, azimuth, tilt angle, and circuit configuration. Furthermore, review loss conditions such as shading, temperature, wiring, and soiling, and run the simulation. Finally, check the annual energy generation, monthly generation, and the breakdown of losses, and determine whether the results are consistent with the site conditions and design conditions.

In practice, the important thing is not to extract the power generation figures alone and make judgments. Simulation results are estimates based on input conditions. If the conditions change, the results change. Therefore, when checking power generation, you must always treat it together with the assumptions. In particular, installation location, weather data, system capacity, azimuth, tilt angle, shading conditions, and loss settings should be organized so they can be explained later.

Furthermore, PVSyst results are relevant not only to design studies but also to site management. To reproduce the layout and conditions from the simulation on site, accurate surveying, position control, and construction verification are required. To apply the results of power generation studies to the actual construction of a power plant, it is important to treat desk calculations and on-site information together rather than separately.

If you are not yet familiar with using PVSyst, the quickest approach is to first grasp the basic steps to obtain the energy yield and then learn how to interpret the results. As you become more comfortable with the operations, move on to comparing multiple conditions, checking shadow details, scrutinizing loss conditions, and cross-checking against site conditions so you can verify energy yield in a way that better matches practical work.

In the design and construction of solar power plants, it is important to manage simulation results linked to on-site layout, pile locations, terrain, and construction progress. PVSyst-verified conditions can be connected to actual site management by managing design-stage input parameters, construction-stage positional information, and operational performance data together rather than separately. By establishing a framework that consistently handles everything from power generation assessment to on-site verification, simulation results can be more readily applied in practice.