What is PVSyst? Six Perspectives to Avoid Failure in Power Generation Forecasting

PVSyst (official notation: PVsyst) is analysis software used for design studies, sizing, energy production simulation, and loss analysis of photovoltaic power generation systems. Users input the plant location, meteorological data, azimuth, tilt angle, module capacity, power conditioners, shading, wiring losses, temperature losses, and other conditions to check the expected energy production and the breakdown of losses.

However, the results from PVSyst are "simulation results based on the input conditions" and do not guarantee actual power generation. If you judge solely by the annual generation figures, you may overlook assumptions such as the representativeness of meteorological data, the handling of shading, loss settings, equipment configuration, and stoppage conditions, which can lead to discrepancies with actual results after the start of operation and to misunderstandings among stakeholders.

This article explains six ways to review PVSyst for practitioners investigating "What is PVSyst" for the first time, to avoid mistakes in power generation forecasting. Rather than simply looking at the resulting generation, checking in the sequence of input conditions, meteorological data, equipment conditions, loss settings, month-by-month and phase-by-phase results, and how to use the report will make the estimates easier to apply to design reviews and business decision-making.

Table of Contents

• What PVSyst is used to analyze

• How to read 1: Read power generation forecasts by reverse-calculating from the input conditions

• How to read 2: Verify the assumptions for meteorological data and installation conditions

• How to read 3: Examine the module and power conditioner (inverter) conditions

• How to read 4: Interpret loss settings as causes of differences in power generation

• How to read 5: Look not only at annual energy production but also by month and by stage

• How to read 6: Points to note when using report results for practical decision-making

• Information to organize before using PVSyst

• Summary: In power generation forecasts, it is more important to examine the assumptions than the numbers

What is PVSyst used to analyze?

PVSyst is analysis software used to evaluate the energy production and loss structure of photovoltaic systems at the design stage. In a solar power plant, energy production varies according to many factors, including the installation location, azimuth, tilt angle, module capacity, equipment configuration, shading effects, wiring losses, and temperature losses. PVSyst is used to input these conditions and, based on meteorological data and system parameters, estimate annual and monthly energy production.

In practice, the role of PVSyst is not simply to predict how much electricity a plant will generate. What matters is clarifying which assumptions are being made, where and to what extent losses occur, and how they ultimately affect the final energy yield. The predicted generation figures are used for design studies, business planning, financial assessments, pre-construction checks, and comparisons with actual performance after commissioning, but those numbers are the result of the combination of the input assumptions.

For example, even solar power plants with the same installed capacity will have different solar irradiance conditions depending on the installation site. If the tilt angle or azimuth changes, the irradiance incident on the module surface also changes. Shading effects vary with the surrounding topography and the arrangement of the racking, and electrical losses change depending on wiring distances and equipment configuration. In other words, the generation shown by PVSyst is not determined by installed capacity alone; it must be considered as the cumulative result of site conditions and design parameters.

Many people who search for "What is PVSyst" are likely not only looking for an overview of the software but are also unsure where to look in reports, how to assess the validity of projected energy production, and how to verify materials submitted by designers or external contractors. For those receiving a power generation forecast, what matters more than understanding every technical formula is being able to discern which assumptions the results are based on.

When reviewing PVSyst results, it's important not to be reassured by looking only at the annual energy production. Annual energy production is an easy-to-understand metric, but behind it are factors such as irradiance conditions, temperature conditions, shading, equipment efficiency, DC-side losses, AC-side losses, and assumptions about downtime and power curtailment. If any of these diverge from actual site conditions, even a report that appears well put together can easily differ from actual operational performance.

Therefore, in practice, it is more useful to regard PVSyst not as "software that produces energy estimates" but as "software that visualizes the assumptions behind energy production and the loss structure." If you can confirm which inputs strongly affect energy production, which losses are large, and which conditions remain uncertain, it becomes easier to use for design changes and risk explanations.

Perspective 1: Read power generation forecasts by reverse-calculating from the input conditions

The first thing to check to avoid mistakes in PVSyst power yield forecasts is not the resulting numbers, but to read them by working backwards from the input conditions. If you only look at the power output figures, comparisons and judgments may seem easy. However, simulation results are heavily dependent on the assumptions entered. If those assumptions do not match actual site conditions, no matter how well-crafted the report is, it can lead to incorrect practical decisions.

In power generation forecasting, we first check whether basic information such as installed capacity, installation location, azimuth, tilt angle, number of modules, series‑parallel configuration, inverter configuration, and grid connection conditions is correctly reflected. Errors at this stage can have a greater impact than the detailed loss settings applied in later steps. For example, if the entered tilt angle differs from the design drawings, or if the way orientation is handled is misaligned with the actual site, the way solar irradiance is received will change, affecting not only the annual energy yield but also the monthly generation trends.

Next, when reading PVSyst results you need to separate which conditions are confirmed information and which are assumptions. Some conditions are relatively easy to confirm, such as the installation location and system capacity, while others—like the effects of soiling, downtime, long-term degradation, and operational constraints—are treated as assumptions on a per-project basis. If you treat parts that are largely assumptions as if they were confirmed information, the generation forecast can be perceived as overly precise.

In power generation forecasting, it's important not only to check whether the results look good but also to understand why they are that way. Even if the annual energy production appears high, there may be issues such as lax loss settings, insufficient accounting for shading effects, or temperature conditions that do not match the actual site conditions. Conversely, if the energy production appears low, there may be reasons like using conservative assumptions, treating shading and losses more strictly, or having long-term operation in mind.

In practice, you may need to compare multiple estimation results. In such cases, it is dangerous to compare them based only on the amount of power generated. If each estimate uses different weather data, loss settings, treatment of shading, equipment conditions, or definitions of installed capacity, a simple comparison is not possible. When comparing, you must align the assumptions and then confirm which changed condition caused the change in power generation.

When you receive a PVSyst report, first review the list of input conditions and cross-check them against the design drawings, equipment list, layout plan, and site conditions. In particular, capacity, number of modules, orientation, tilt, mounting surface, and the configuration of the DC and AC sides are areas where stakeholders’ understandings easily diverge. If you discuss the validity of the generation estimate without confirming these, differing assumptions often emerge later, leading to reworking documents and repeating explanations.

Power generation forecasts do not fully guarantee future performance. That is why it is important to carefully review the input conditions and understand the nature of the predicted values. The first step to correctly interpreting PVSyst is not to trust the generation figures, but to check which assumptions those figures are derived from.

Perspective 2: Confirm assumptions about meteorological data and installation conditions

In PVSyst energy yield forecasts, the next important step is to verify the assumptions for the meteorological data and installation conditions. Solar power output is heavily influenced by irradiance and temperature. Even with the same system configuration, if the meteorological data used or the installation conditions change, the predicted results will change. Therefore, meteorological conditions should not be treated as mere background information but read as central assumptions of the energy yield forecast.

When reviewing meteorological data, first confirm that the data point corresponds to the actual location of the power plant. If the power plant's location and the meteorological station are far apart, regional climate differences and elevation changes can cause discrepancies in solar irradiance and temperature conditions. This is especially true in mountainous areas, coastal regions, snowy areas, locations prone to fog, and places with surrounding terrain variations, where using data from nearby stations may still differ from actual conditions.

Also, it is necessary to check the type and period of the meteorological data. Whether you are using data close to a long-term average or measured values for a specific year changes the meaning of the results. Meteorological data for a specific year can be useful for explaining that year’s power generation, but caution is required when using it as an average for long-term business planning. When using power generation forecasts for financial assessments or explanations of long-term operation, confirm the representativeness of the meteorological data.

Not only solar irradiance but also ambient temperature affects power generation. Photovoltaic modules tend to lose output as temperature rises, so how ambient temperature conditions and module temperature are handled is important. Even in regions with high annual irradiance, temperature losses can increase if high-temperature conditions are strong. Conversely, during seasons with low ambient temperatures, efficiency can be advantageous if irradiance conditions are sufficient. When examining monthly generation trends, it is important to check both irradiance and temperature conditions together.

For installation conditions, orientation (azimuth) and tilt angle are fundamental. Generally, to increase power generation it is important to arrange the system to receive solar radiation efficiently, but in actual design one must also consider land topography, site preparation conditions, row spacing, drainage, maintenance access, wind loads, snow loads, and surrounding structures. Therefore, rather than pursuing only the ideal angle, it is necessary to verify that the installation conditions take into account the constraints of the entire site.

The impact of shadows from terrain and surrounding objects is also important. Shadows not only reduce energy production but also affect monthly variability and time-of-day output. The effect of shading tends to be greater during winter when the sun elevation is low, in the morning and evening hours, in layouts with closely spaced rows, and where there are trees or buildings nearby. How well PVSyst accounts for shadows influences the reliability of energy production forecasts.

However, more detailed shadow settings do not necessarily mean they are correct. Even if you build a detailed model, discrepancies between predictions and actual results will arise if the terrain data, obstacle heights, tree growth, or post-construction conditions differ from reality. Conversely, at sites where the impact is small, a simplified treatment may be sufficient for practical decision-making. The important thing is to confirm whether the shadow settings have an appropriate level of granularity for the site’s risks.

In snowy regions, special attention must be paid to how snow is handled. Snow can greatly affect power generation, but standard meteorological data alone may not accurately represent how snow will persist or when it will shed. Site conditions that change over time—such as snow cover, fallen leaves, soiling, and tree growth—should be described under separate assumptions as needed.

Meteorological data and installation conditions form the foundation of energy yield forecasts. If this foundation is off, the validity of the final results will be reduced even if loss settings and equipment parameters are adjusted in detail. When reviewing a PVSyst report, you need to check—before looking at the energy yield figures—which location’s meteorological data were used, what azimuth and tilt were assumed, and what shading conditions were modeled.

View 3: Check the Module and Power Conditioner Conditions

Verifying the conditions of the modules and power conditioners is essential when interpreting PVSyst results. In a solar power installation, the solar modules generate DC power and the power conditioners convert it to AC power. This combination affects not only the energy output but also output limitations, conversion efficiency, the ratio of DC to AC capacity, and the margin for temperature conditions.

First, I want to confirm whether the module specifications match the design documents. I check that the output, number of modules, series/parallel configuration, temperature characteristics, handling of degradation, and allocation per mounting surface are correct. The total module output serves as the basis for system capacity and power generation, so an error here will skew the overall estimates. In particular, for projects with multiple mounting surfaces or for projects where equipment specifications were changed midway, be careful to ensure that old conditions haven't been left in place.

Next, check the capacity of the power conditioner and the input conditions. The relationship between the DC-side module capacity and the AC-side conversion capacity affects power generation and output limits during peak times. If the DC capacity is designed larger than the AC capacity, output may be limited during periods of strong insolation. On the other hand, considering operation during mornings, evenings, and cloudy periods, designing a larger DC side can contribute to power generation and project economics. What matters is how that approach is reflected in the report.

When evaluating combinations of equipment, we check not only whether capacity is sufficient, but also whether the operating voltage range, input current, temperature conditions, and string configuration are met. Module voltage varies depending on the site's minimum and maximum temperatures. Since voltage tends to rise at low temperatures and fall at high temperatures, it is important to confirm that it stays within the equipment's allowable range. Even if PVSyst results look clean, if there is insufficient design margin, operational constraints may arise in actual use.

Also, under equipment conditions, conversion efficiency and behavior at partial load also affect power generation. The system does not operate near its rated capacity throughout the year. There are periods of low output, such as mornings and evenings, during cloudy weather, in winter, or when shading occurs. Therefore, it is important to look not only at the rated efficiency but also at what kinds of losses are expected across the actual operating range.

In PVSyst, module and power conditioner conditions are set as data, but the project personnel must verify that that data matches the latest design conditions. It is not uncommon for equipment specifications to change at the quotation, design, and construction stages. If the conditions at the time a report is produced differ from the current planned conditions, using the energy yield forecast as comparative or explanatory material can cause problems.

Checking the modules and power conditioners relates not only to the validity of the generated energy but also to design safety and operational risks. When reviewing PVSyst results, it is important to confirm that capacity, configuration, voltage, current, efficiency, and the approach to output limiting align with the design intent, rather than being distracted by minor differences in equipment names.

Perspective 4: Interpreting Loss Settings as the Cause of Power Output Differences

One important thing to check when using PVSyst in practice is the loss settings. The generation forecast does not simply show the amount that would be produced under ideal irradiance conditions. In reality, generation is reduced by various factors such as temperature, shading, soiling, wiring, conversion, equipment characteristics, downtime, and long-term degradation. In PVSyst reports, these losses are reflected step by step, and the final energy production is calculated.

When reviewing loss settings, first identify which losses are large. If there are significant losses, consider separately whether they are reasonable given site conditions, whether they can be improved through design, or whether they can be mitigated by maintenance or operation. For example, if shading losses are large, there may be room to reconsider layout, row spacing, surrounding obstacles, installation height, and so on. If wiring losses are large, this may lead to re-evaluating cable length, conductor cross-sectional area, and equipment placement.

Temperature loss is a basic loss that occurs at many solar power plants. While stronger solar irradiance increases generation, output decreases as module temperature rises. Therefore, in high-temperature regions, rooftop installations, and installation conditions with poor ventilation, the assessment of temperature loss becomes important. Underestimating temperature loss can sometimes be the reason why actual generation appears lower than predicted.

Losses due to soiling are also a practical consideration. Causes of soiling—such as windblown dust, pollen, bird droppings, fallen leaves, and residuals after snowfall—vary by region and installation environment. Soiling losses should not be set uniformly; their appropriateness needs to be assessed based on site conditions and cleaning policy. The long-term outlook for power generation differs between sites where little or no cleaning is assumed and those where regular washing and inspections are performed.

Wiring losses and conversion losses are aspects closely related to design quality. Under conditions such as long wiring distances, large voltage drops, inefficient equipment layouts, or complex junction boxes and collector routes, losses may increase. Even if loss rates are set in PVSyst, you must verify that their basis corresponds to the actual wiring plan. If provisional values are used, they should be reviewed after detailed design.

Assumptions about outages and availability are also important. Power plants do not always operate in ideal conditions: inspections, failures, grid-side constraints, communication problems, maintenance work, shutdowns after natural disasters, and so on. The degree of assumed outages and grid constraints has a major impact on the business plan. Estimates that assume zero downtime may be usable for initial assessments, but should be treated cautiously when forecasting long-term operations.

When looking at losses, it is important not to simply add loss rates. In PVSyst’s loss diagram, each loss may be shown as a percentage relative to the energy amount at the previous stage. Therefore, if you simply sum multiple loss rates and treat that as the total loss, the result may not match the actual outcome. You need to read the losses while checking at which stage and against what they occur.

Loss settings can be used not only as indicators of factors that reduce energy production but also as information to visualize risks. By understanding which losses are large, it becomes easier to prioritize design improvements, construction management, maintenance planning, and operations management. What is important when interpreting PVSyst is not to read losses as mere numbers, but to organize them as candidate causes when a difference in energy production occurs.

Perspective 5: Consider not just annual power generation but also monthly and by process

When looking at a PVSyst report, the first thing many people check is the annual energy production. The annual energy production is undeniably an important metric because it is directly linked to project feasibility and financial planning. However, if you judge based only on the annual production, you may overlook the details of the production forecast. To avoid mistakes in energy production estimates, it is necessary to also check monthly trends and the stages at which losses occur.

Looking at monthly power generation reveals seasonal characteristics. It is natural that months with high solar irradiance have higher generation, but monthly results vary depending on temperature, snowfall, the rainy season, typhoons, and how shadows lengthen. For example, in summer there is a lot of sunlight, but temperature-related losses may increase. In winter, lower temperatures can sometimes be advantageous for efficiency, while shorter daylight hours, shading, and snowfall can have an impact. If monthly generation differs significantly from the region’s climatic intuition or site conditions, you should check the input conditions.

Also, monthly generation is useful for comparing actual performance after operation begins. Even if there appears to be little difference on an annual basis, monthly data may show large deviations in specific seasons. In such cases, it becomes easier to distinguish whether the cause is interannual variation in weather conditions, insufficient shading settings, the effects of soiling or snow accumulation, or equipment outages. If you use PVSyst results for performance management, it is important to save monthly values as well as annual values.

A process-by-process perspective is also indispensable. Here, "process-by-process" does not mean construction stages but the loss processes that occur as solar irradiance is incident on the module surface, is converted into direct current (DC) power, passes through wiring and equipment, and is output as alternating current (AC) power — in other words, the stages through which generation is reduced before reaching the final value. By identifying which stage is experiencing the largest losses, it becomes easier to understand why power generation is low.

For example, if the solar irradiance on the incident surface is low, you question the installation orientation and tilt, weather conditions, and shading assumptions. If losses on the DC side are large, you check temperature, mismatches, soiling, wiring, and equipment combinations. If losses on the AC side are large, you need to look at conversion efficiency, output limitations, AC wiring, and equipment capacity considerations. By reading it broken down by process, the energy production figures become information with identifiable causes rather than mere results.

Even when comparing options, viewing results by month and by phase is useful. When comparing multiple layout proposals or equipment configurations, annual power generation alone does not reveal the reasons for differences. One proposal may have higher annual generation but suffer significant shading effects in certain seasons. Another proposal may have slightly lower annual generation but a more stable loss structure and lower maintenance and construction risks. In practical decision-making, it is important not only to look at the amount of generation but also to understand the structure behind how that generation is produced.

When using probabilistic perspectives such as P50 or P90, it's important not to confuse annual values with monthly values. Long-term power generation risk is often evaluated on an annual basis, and monthly results can fluctuate significantly due to year-to-year weather variability. Rather than treating monthly estimates as guaranteed values, it's safer to use them as inputs for seasonal trend and variance analysis.

When you're not yet familiar with PVSyst, you inevitably focus on the final generation figures. However, to improve the reliability of generation forecasts, you need to check monthly trends together with losses by process. Annual generation is the conclusion, and the monthly and process-specific information are the steps that lead to that conclusion. Being able to interpret this process is important for using PVSyst effectively in practice.

Perspective 6: Precautions When Using Report Results for Practical Decision-Making

PVSyst reports are a useful resource for explaining power generation forecasts. However, just because a report is well formatted does not mean it can be used directly for practical decision-making. When using power generation forecasts for design, investment decisions, construction management, maintenance planning, or customer briefings, it is necessary to clarify which stage’s conditions the report figures are based on.

First, it is important not to treat simulation results as guaranteed values. PVSyst results are forecasts based on input conditions and meteorological data. Actual energy production will vary due to year-to-year weather fluctuations, construction quality, individual differences in equipment, soiling, outages, maintenance status, and changes in the surrounding environment. Therefore, you should avoid presenting the report’s estimated generation as “this number will definitely be achieved.” In practice, the forecast, the underlying assumptions, and the factors that can cause variation should be explained together.

Next, it is important to check the point in time when the report was created. In solar power plant planning, conditions can change between the initial study, basic design, detailed design, pre-construction, and post-construction stages. If equipment capacity, layout, tilt, wiring, the surrounding environment, or grid conditions have changed, using an old report as-is may not align with the current plan. Before using any materials, you must confirm which stage of design conditions the report corresponds to.

Also, when sharing reports internally and externally, it is important to supplement explanations according to the reader’s level of understanding. Loss items that are obvious to designers may be difficult to understand for sales staff, customers, financial stakeholders, or construction personnel. Simply listing technical terms does not convey the validity or risks of the estimated power generation. You need to explain, in practical terms, the reasons why the power generation is high, the reasons why it is low, the items that should be managed through maintenance, and the aspects that are likely to fluctuate in the future.

When using PVSyst reports, pay attention to how numbers are rounded and to the units. Several similar indicators appear, such as annual energy production, energy production per unit of installed capacity, performance ratio, and loss rates. Comparing them without understanding differences in units or denominators can lead to incorrect conclusions. In particular, you should check whether values are based on DC capacity or AC capacity, and which time period the values refer to.

Furthermore, power generation forecasts are not something you create once and then finish. If there are design changes or changes in construction conditions, they should be reviewed as needed. Use them as rough estimates in the initial stages, scrutinize the conditions during the detailed design phase, and compare them with actual performance after commissioning—the way you use the forecasts will change. It is practical to treat PVSyst reports not as fixed deliverables but as management documents that are updated as the project progresses.

Finally, when using report results as a basis for decision-making, you need to consider not only energy production but also the feasibility of design, construction, and maintenance. Even if the energy output is high, if construction is difficult, maintenance access is poor, shading risk remains, or the plan is vulnerable to future environmental changes, it may not be considered a good plan overall. PVSyst results are an important input for decision-making, but you should not determine the entire plan based on them alone; it is essential to evaluate them together with site conditions and operational policies.

Information to prepare before using PVSyst

To use PVSyst effectively, it is important to organize the necessary information before operating the analysis software. If you proceed with calculations while input conditions remain ambiguous, you are likely to discover differing assumptions later, which can lead to redoing reports and re-explaining things to stakeholders. To improve the accuracy of energy yield predictions, not only the settings in the software but also the quality of the preparatory work has a major impact.

First, what needs to be organized is the basic information of the power plant. Confirm the location, site area, topographical conditions, orientation, tilt, mounting conditions, surrounding obstructions, and the approach to grid connection. In particular, because the location affects the selection of meteorological data and solar irradiance conditions, it is desirable to clarify the actual installation position, not just a rough address. For large-scale power plants or sites with elevation differences, conditions may vary even within the site.

Next, organize the equipment configuration. Confirm module output, the number of modules, allocation for each mounting surface, string configuration, power conditioner capacity, junction boxes, wiring routes, and the relationship with the power receiving and transforming equipment. When equipment has not yet been finalized, it is important to explicitly state these as assumed conditions. Treating a generation forecast produced under provisional conditions as if it were based on finalized conditions will make later explanations difficult.

Information about shading should also be organized in advance. Identify elements that could cause shading, such as surrounding buildings, trees, slopes, mountains, utility poles, fences, adjacent equipment, and shading between module rows. Even if drawings appear problem-free, shadows can lengthen in winter and during mornings and evenings. In particular, if the impact of shading is underestimated at the design stage, it is likely to appear as a difference in power generation after commissioning.

For loss conditions, it is useful to organize internal standards and project-specific approaches. If you set factors like soiling, downtime, wiring, degradation, temperature, output limits, and maintenance policy by feel each time, it becomes difficult to compare across projects. It is not necessary to make the conditions exactly the same, but it is important to be able to explain why you adopted those values. The reliability of power generation forecasts depends not only on the settings themselves but also on whether you can explain the rationale behind them.

It is also important to consider in advance who will see the output report. The information to emphasize differs for internal review, customer presentations, pre-construction checks, materials for financial institutions, and maintenance planning. Internal technical reviews require detailed losses and configuration conditions, whereas customer-facing explanations need the assumptions, the meaning of predicted values, and risk factors to be clearly organized. Deciding which information to emphasize according to the intended use makes the report more practical for actual work.

When preparation before using PVSyst is complete, the analysis itself becomes more efficient. If necessary information is lacking, work will be interrupted mid-operation, provisional settings will increase, and the explanatory power of the results will decline. On the other hand, if the location, design conditions, equipment configuration, shading conditions, loss policy, and intended use of the output are organized, it becomes easier to share the energy yield prediction results with stakeholders. To master PVSyst, not only software operation but also the organization of information before input is indispensable.

Summary: In power generation forecasts, it is more important to look at the assumptions than the numbers

PVSyst is analysis software used to predict the power output of solar power plants and to organize design conditions and loss parameters. It not only allows you to review estimated power generation results, but also helps you understand which conditions affect output, which losses are significant, and which aspects of design or operation should be reconsidered.

However, the results from PVSyst are predictions based on the input conditions and do not guarantee actual energy production. If meteorological data, installation conditions, equipment configuration, loss settings, the treatment of shading, or assumptions about outages and maintenance change, the predicted energy output will also change. Therefore, it is important not to judge solely by the annual energy production figure, but to verify the assumptions from which that figure was derived.

To avoid mistakes when forecasting power generation, first check the input conditions, then review the meteorological data and installation conditions. After that, verify in order the configuration of the modules and power conditioners, loss settings, monthly generation, process-specific losses, and the intended use of the report. By following this sequence you can interpret PVSyst results not as mere numbers but as information usable for design and business decisions.

In practice, it is important to connect power generation forecasts with on-site conditions. If generation is lower than expected, it is necessary to distinguish whether it is due to interannual weather variability, shading, soiling, equipment downtime, or differences in design conditions. Conversely, if losses and risks are organized at the estimation stage, they can be more readily applied to design improvements and maintenance planning.

In solar power plant planning, when simulation, design, construction, and operations management are fragmented, the assumptions behind generation forecasts are less likely to be carried through to the field. To make PVSyst results more practically useful, it is important not to stop at the analysis report but to manage and link site conditions, design information, construction records, and operational performance.

If you want to apply power generation forecasts to site management and design reviews, a system that accurately captures on-site conditions and links them to design information is useful, not just desk-based estimates. If you can manage PVSyst-organized power generation forecasts together with site inspections, construction records, maintenance checks, and actual generation performance, it becomes easier to analyze the differences between predicted and actual values and to feed those insights into subsequent design and operational improvements.