5 Key Result Screens to Check in the PVSyst Manual

Table of Contents

• What is the PVSyst results screen used to view?

• Prerequisites to keep in mind before viewing the results screen

• Results screen — 5 points, 1. Annual power generation is the entry point for assessing business viability

• Results screen 5 Point 2 Compare projects with Specific Production

• On results screen 5, point 3, verify the design quality using Performance Ratio

• Break down the causes of loss on the Results screen 5.4 Loss Diagram

• Result screen 5 point 5 Find anomalies in monthly and hourly results

• Judgment errors to avoid when reading the results screen

• Verification Procedures for Applying the PVSyst Manual in Practice

• Summary

What is the purpose of the PVSyst results screen?

When conducting a generation simulation while following the PVSyst manual, what many people first get confused about is how to read the results screen. On the input screens you set, one by one, the meteorological data, modules, inverters, azimuth, tilt angle, wiring, shading, loss conditions, and so on. However, what is ultimately required in practice is how the input conditions are reflected as energy production, losses, and performance indicators.

The PVSyst results screen is not merely a place to see “how many kWh will be generated annually.” It is a screen for checking whether the generated energy is reasonable, where the design weaknesses are, whether there are any unnatural input conditions, and which option is advantageous when compared with alternatives. Especially in solar power design and project appraisal, the simulation values may be used directly for revenue and expense calculations, consideration of equipment capacity, explanatory materials for financial institutions and clients, discussions with EPC contractors, and assumptions for O&M planning. Therefore, it is insufficient to read the results screen only superficially.

PVSyst's official documentation also explains that the results include many simulation variables and can be displayed or exported as monthly, daily, hourly, and sub-hourly values, and that the Loss Diagram is particularly useful for identifying weaknesses in system design. In other words, the results screens are not only for producing final reports but also serve as practical verification screens for rechecking the validity of a design.

This article summarizes five points to prioritize when reading the results screens in the PVSyst manual. It can serve both as a foundation for beginners to understand the meaning of the numbers and as a checklist for practitioners to reduce errors before submitting reports.

Important assumptions to understand before viewing the results screen

To read the PVSyst results screen correctly, it is important not to view the result numbers in isolation. Solar power generation simulations combine input conditions and results. You cannot simply judge a design as good because the annual energy production is large or bad because it is small. If the solar irradiance at the installation site, system capacity, module specifications, inverter capacity, presence or absence of shading, temperature conditions, wiring distances, or system configuration differ, the results will also change.

For example, even for the same 1000 kW power plant, annual electricity generation can vary greatly between regions with good solar irradiance and regions that are heavily affected by snow or shading. Also, when the azimuth or tilt angles are different, not only the annual generation but the monthly generation trends and the hourly output curves change. When viewing the results screen, you should first confirm "under which conditions the results were calculated."

Another important point is that the PVSyst results are “predicted values” and not actual measured results. Simulations are calculated based on the meteorological data, equipment specifications, loss conditions, shading conditions, and so on that you input. Therefore, if the input values are overly optimistic, the results will be optimistic as well, and if you use conservative assumptions, the results will be conservative. When reading the results screen, it is essential to evaluate whether the assumptions behind the numbers are reasonable, rather than focusing solely on the numbers themselves.

Also, the results screen displays several indicators: Annual Energy Production, Specific Production, Performance Ratio, Loss Diagram, monthly graphs, hourly data, and so on, each serving a different role. Annual Energy Production is directly tied to project finances; Specific Production makes it easy to compare generation efficiency per unit of installed capacity; Performance Ratio is an indicator for understanding the overall performance of the system. The Loss Diagram is used to track where and to what extent losses are occurring.

When studying the results screens in the PVSyst manual, it is important not to memorize a single number but to read multiple results in conjunction. Reviewing annual energy production, performance indicators, loss structure, and monthly trends in sequence will make the simulation results more convincing.

Results Screen 5 Points 1 Annual Power Generation Is the Entry Point for Business Viability Assessment

On PVSyst’s results screen, the figure that most readily draws attention is the annual electricity generation. In a power generation project, how much energy is produced annually forms the basis for revenue from electricity sales and the benefits of self-consumption. Therefore, annual electricity generation is one of the most important indicators and serves as the entry point for assessing project viability.

However, when looking at annual energy production, what you need to pay attention to is "at which point the energy value is measured." In a photovoltaic (PV) system, the irradiance received by the modules is converted into DC power, which is then converted to AC by the inverter and, if necessary, passes through transformers and power-receiving equipment before finally being sent to the grid or to demand-side equipment. Various losses occur during this process. Therefore, it is necessary to understand whether the generation figure shown on the results screen refers to array output, inverter output, or a value close to the point of interconnection to the grid.

One thing beginners often overlook is looking at annual power generation alone and judging it as "higher than expected" or "lower than expected." However, annual generation becomes much less meaningful unless it is considered together with the installed capacity. You cannot judge the quality of a design by directly comparing the generation produced by a 2 MW system with that produced by a 500 kW system. What becomes important here is the Specific Production, which will be explained next.

Annual energy generation is a figure that is often entered into business plans and financial models. Therefore, before submitting the final report, always verify the consistency between the calculation conditions and the annual energy generation. By reviewing whether the plant capacity is correct, the number of modules is as intended, the inverter configuration contains no errors, the weather-data location is close to the project site, and shading conditions are reflected, you can prevent simple configuration mistakes.

Annual energy production is also used to compare multiple options. For example, when comparing options that change the tilt angle, azimuth, inverter capacity, or module layout, lining up each option’s annual energy production lets you see which option is advantageous in terms of energy output. However, judging by generation alone can overlook clipping caused by oversizing, increased shading losses, longer wiring distances, and higher initial investment.

Therefore, while annual energy generation should be emphasized as an entry point on the results screen, it is important not to draw conclusions from it alone. After confirming the annual generation, you can assess the validity of the results more deeply by proceeding to review productivity per unit of installed capacity, the Performance Ratio, the loss structure, and monthly trends.

Results screen 5 Point 2 Compare projects with Specific Production

The next thing to check on PVSyst’s results screen is the Specific Production. This is generally used as an indicator representing the annual electricity production per unit of installed capacity. In PVSyst’s documentation, Specific Production is described as the annual production per installed capacity, expressed in kWh/kWp/year.

The reason Specific Production is important is that it makes it easier to compare projects with different system sizes. If you only look at annual generation, figures tend to be larger for projects with greater capacity. However, by looking at Specific Production you can see how much is generated per kWp per year, making it easier to compare generation efficiency even between a 100 kW rooftop installation and a 2 MW ground-mounted installation.

For example, even if a project's annual power generation is large, if the installed capacity is very large, the generation per unit of capacity may not be that high. Conversely, even if the total annual generation is small, there are projects that generate power efficiently with limited capacity. Specific Production is an indicator for distinguishing this difference.

When reading the results screen in the PVSyst manual, it is important to consider Specific Production together with regional characteristics, installation conditions, and shading conditions. Specific Production tends to be higher in regions with good solar irradiance and lower in locations with significant shading or heavy snow impact. In addition, azimuth and tilt angles that deviate from optimal conditions will also affect Specific Production. For rooftop projects, since the system must conform to the roof shape, it is not always possible to achieve ideal azimuth or tilt angles. In such cases, a lower Specific Production may be the result of site conditions rather than a design error.

Practical points when looking at Specific Production are to separate comparisons within the same project from comparisons with similar projects. Within the same project, you can compare proposals that change the tilt angle, proposals that change the panel layout, proposals that implement shading mitigation, etc., and consider which proposal can increase generation per unit of capacity. On the other hand, when comparing with similar projects, you need to confirm that assumptions such as region, meteorological data, installed capacity, module type, and installation method are similar. Comparing projects whose assumptions differ too much will not lead to accurate conclusions.

Also, be cautious if the Specific Production is higher than expected. Even if the results look good, there may be insufficient loss settings, missing shading conditions, underestimated wiring losses, or meteorological data that do not match the project site. Conversely, if it is too low, suspect input errors in azimuth or tilt, incorrect module count settings, excessive shading losses, or inconsistencies in the inverter configuration.

Specific Production is a fundamental indicator for understanding PVSyst results in a "scale-independent" way. By checking it together with annual energy production, you can judge not just whether the total generation is high or low, but whether the installation is generating efficiently.

Result Screen 5 Point 3: Verify Design Quality with Performance Ratio

One of the metrics you should always check on PVSyst’s results screen is the Performance Ratio, or PR. PR is a widely used indicator for grasping the overall performance of a photovoltaic (PV) system. In PVSyst’s documentation, PR is explained as the ratio showing how much of the energy that would be produced if the system continuously operated at its rated STC efficiency is actually and effectively produced.

One convenient aspect of PR is that it smooths out, to a certain degree, the effects of solar irradiance and system capacity, making it easier to evaluate system-wide losses and performance. Even if annual generation is large, it will naturally be higher in regions with very good solar irradiance. Conversely, by looking at PR you can check how efficiently the system is extracting energy relative to the input irradiance conditions.

In PVSyst’s official documentation, PR is described as including optical losses such as shading, IAM, and soiling; PV conversion, degradation, module quality, mismatch, wiring and other array losses; and, for grid-connected systems, system losses such as inverter efficiency. In other words, PR is not the performance of a single piece of equipment but a comprehensive metric reflecting the losses of the entire design.

When looking at PR, it is important not to simply assume that a high value is necessarily good or a low value necessarily bad. For example, in snowy regions, locations with heavy shading, complex roof geometries, or projects with split orientations, there are many factors that can reduce PR. This may not be a design mistake but rather a result reflecting site conditions. Conversely, if PR is unnaturally high, it may indicate that loss conditions have not been sufficiently accounted for. In particular, if settings for soiling, temperature, wiring, mismatch, shading, or degradation are overly optimistic, PR will appear artificially high.

In practice, when evaluating PR it is useful to compare multiple options for the same project. For example, check whether PR has improved for an option that implemented shading countermeasures, whether losses have decreased for an option that revised the wiring plan, and how clipping and conversion losses changed for an option that altered the inverter configuration. PR is an easy-to-use numerical metric that serves as a common indicator for assessing the effects of design changes.

Also, PR is a metric that is often used in explanatory materials. For the client and other stakeholders, rather than simply stating “the annual power generation is this value,” explaining that “this result indicates the degree of performance relative to the solar irradiance conditions” helps deepen understanding of the simulation. However, to avoid misunderstanding the meaning of PR, it is necessary to add that it is an indicator of the system’s overall efficiency, not the power generation itself.

When learning the results screen in the PVSyst manual, it is important to look at PR together with annual energy production and Specific Production. If annual energy production is high but PR is low, the result may be aided by favorable solar irradiation conditions or by the installed system capacity. If Specific Production is low and PR is also low, there may be room for improvement in the design conditions and loss settings. PR is a central indicator for interpreting the results screen values in a multi-dimensional way.

Results screen 5 Point 4 Decompose the causes of loss with the Loss Diagram

One of the most practically useful features on PVSyst’s results screen is the Loss Diagram. The Loss Diagram shows, step by step, where and how losses occur as the generated energy becomes the final usable energy. In PVSyst’s documentation, the Loss Diagram is presented as a tool to quickly assess the quality of a PV system design and to identify the main loss factors.

By looking at the Loss Diagram, you can move beyond the simple result of "low power output" and determine "why it is low." Losses in photovoltaic power generation stem from various factors, including losses due to incident solar irradiance conditions, shading from nearby obstacles, IAM, soiling, temperature, module quality, mismatch, wiring, inverters, transformers, and grid-side losses. By tracking these one by one, the areas that need improvement become clear.

For example, if shading losses are large, there may be room to revisit the panel layout, obstacle conditions, racking height, and row spacing. If temperature losses are large, check the mounting configuration, ventilation conditions, module characteristics, and local ambient temperature conditions. If wiring losses are large, consider cable length, conductor cross-sectional area, and the locations of combiner boxes and inverters. If inverter losses or clipping are significant, review the DC/AC ratio, inverter capacity, and string configuration.

The strength of the Loss Diagram is that it can "visualize" losses. Designers can explain the causes of reduced power generation by category rather than by intuition. For example, if a client asks, "Why does this proposal generate less power than the alternative?", checking the Loss Diagram makes it easier to explain whether the difference is due to shading, orientation or tilt, or equipment configuration.

However, caution is required when reading the Loss Diagram. Because loss items depend on the input conditions, losses that have not been configured will, of course, not be reflected in the results. For example, if soiling loss has not been entered, its impact may appear small on the Loss Diagram. If a 3D shadow model has not been created, shading losses from nearby obstructions will also not be adequately reflected. The Loss Diagram presents the results clearly, but its accuracy depends on the accuracy of the inputs.

Also, the Loss Diagram can be used not only for the entire year but also for detailed monthly review. According to PVSyst’s documentation, the Loss Diagram is shown in the simulation report as an annual overview and is also available month by month from the predefined graphs in the detailed results, enabling assessment of seasonality and the impact of each loss.

This is very important in practice. Even if the annual total does not appear to be a major problem, there can be phenomena such as large shading losses only in winter, large temperature losses only in summer, or drops in power generation in specific months. Seasonal changes in solar altitude particularly affect rooftop installations, mountainous areas, and projects with surrounding buildings or trees. By checking monthly trends as well as the annual Loss Diagram, you can reduce the chance of overlooking issues.

When reading the results screen in the PVSyst manual, the Loss Diagram should be treated not as a mere illustrative figure but as a diagnostic tool for improving the design. If the results differ from expectations, checking the breakdown of losses in the Loss Diagram — rather than first re-evaluating the annual energy production — is the quickest way to pinpoint the cause.

Result Screen 5 Point 5 Find anomalies in monthly and hourly results

In PVSyst's results screen, you can view not only annual values but also monthly, daily, and hourly results. After checking the annual energy production, Specific Production, PR, and Loss Diagram, it is important to use the monthly and hourly results to look for any numerical anomalies.

When you look at the monthly results, you can see seasonal generation trends. In general, generation varies month to month due to factors such as solar irradiance, solar altitude, temperature, snowfall, and the effects of the rainy season and cloudy weather. By viewing monthly generation on the results screen, you can understand seasonal variations that are not apparent from the annual total alone. For example, even if solar irradiance is high in summer, temperature losses can be large and generation may not increase as much as expected. Conversely, in spring and autumn temperatures are relatively low and solar conditions are favorable, so generation can be more stable.

Hourly results are useful for more detailed checks. If output suddenly drops during a particular time period, possible causes include shading, inverter limitations, clipping, or inconsistencies in input conditions. If morning or evening output is lower than expected, check for nearby obstructions or the effect of azimuth. If output plateaus around noon, it can be an indication to reassess inverter capacity or the DC/AC ratio.

PVSyst explains that many variables included in the results can be displayed or exported as monthly, daily, hourly, and sub-hourly values. This means that results can be verified not only by annual values but also through detailed time series.

In practice, you can use monthly and hourly results to enhance the explanatory power of generation forecasts. For example, with self-consumption solar PV it is important not only to know the annual generation but also whether the times when generation occurs overlap with demand. You need to consider to what extent generation contributes to daytime peak demand, whether generation falls short during morning and evening demand, and whether it matches demand patterns on holidays and across seasons. By combining PVSyst results with external demand data, you can move beyond simple generation forecasts to more practical evaluations of energy utilization.

Monthly and hourly results can also help detect input errors. Even if the annual energy production looks plausible at first glance, examining the monthly graph may reveal that a particular month is unusually low, or the hourly graph may show an unnatural drop during specific time periods. Mistakes such as selecting the wrong weather data, misconfiguring the shading model, errors in operating conditions, or inconsistencies in system configuration are easier to spot when viewed as time series.

When studying the results screens in the PVSyst manual, it is important not to stop at checking only the annual values. Annual energy production is important, but in actual operation seasonal and time-of-day variations carry significant weight. By reviewing monthly and hourly results, you can increase the reliability and explanatory power of the simulation results.

Judgment errors to avoid when reading result screens

The first premature judgment to avoid when reading PVSyst’s results screen is deciding the quality of a design solely by its annual energy production. Annual energy production is important, but you cannot make a straightforward comparison if the installed capacity, local irradiation conditions, presence of shading, or loss settings differ. Even if the annual energy production is high, the production per unit capacity may be low, the PR may be poor, or the losses may be large.

Another thing to avoid is placing too much emphasis on PR as an absolute measure. PR is a useful indicator for assessing design quality, but the appropriate level varies depending on project conditions. In projects with a lot of shading or with constraints on roof shape, PR can be lower. In such cases, it is more important to check which losses are affecting PR and to what extent, rather than focusing on the low PR itself.

The third error in judgment is failing to check the input conditions even when looking at the Loss Diagram. The Loss Diagram clearly shows the breakdown of losses, but the losses displayed there are based on the input conditions. If shadows are not set, soiling losses are not included, or the wiring conditions do not match reality, the Loss Diagram will not adequately reflect the actual situation. When viewing the results screen, you should always go back and verify the input conditions.

The fourth is overlooking anomalies in monthly or hourly data. Even if the annual values look reasonable, the monthly data may show unnatural seasonality, and the hourly data may show sudden drops during specific periods. In particular, when considering shading, snow, inverter limits, and self-consumption, checking along the time axis is important.

Fifth, treat the results only as numbers for explanatory purposes and do not use them to improve the design. The PVSyst results screen is not the final screen for determining the power generation; it is a feedback screen for reviewing the design. If losses are large, investigate the causes, compare multiple options, and revise the conditions to move closer to a more appropriate design.

Verification Procedures for Applying the PVSyst Manual in Practice

To make use of the PVSyst manual in practical work, it's helpful to decide the order in which you'll view the result screens. The recommended flow is to first check the annual energy production, next use Specific Production to understand the generation per capacity, then check PR to assess the overall system performance, break down loss factors with the Loss Diagram, and finally review the monthly and hourly results to look for any anomalies.

By following this order, you can check the results step by step from a broad perspective to a detailed one. If you look at detailed graphs right away, it becomes difficult to know where to focus. On the other hand, if you stop at annual values alone, cause analysis is insufficient. By reviewing in the sequence of annual generation, Specific Production, PR, Loss Diagram, and monthly and hourly results, you can grasp both the overall picture and the details of the results.

In practice, after checking the results screen you should always return to the input conditions. If the annual energy production is higher than expected, check the meteorological data, loss settings, shading conditions, module capacity, and inverter capacity. If it is lower than expected, check shading losses, temperature losses, wiring losses, clipping, and the azimuth and tilt angle settings. Going back and forth between the results screen and the input screen increases the accuracy of the simulation.

Also, when comparing multiple proposals, it is important to align the comparison conditions. If you compare while meteorological data or baseline loss conditions differ, you will end up comparing differences in assumptions rather than differences in design. For example, when comparing panel layout proposals, meteorological data, equipment specifications, degradation conditions, soiling conditions, and so on should be the same, and you should change only the elements you want to compare, such as the layout or shading conditions.

Before submitting the report, check whether the numbers on the results screen can be explained. Verify why the annual energy production took that value, whether the Specific Production is reasonable compared to similar projects, whether you can explain the reasons for a high or low PR, whether the large loss items shown in the Loss Diagram are acceptable, and whether there are any anomalies in the monthly or hourly trends. If there are any figures you cannot explain, you should review the input conditions and model settings.

Also, when sharing the results screen with stakeholders, it is important to succinctly explain what the metrics mean. For people not familiar with PVSyst, Specific Production, PR, and the Loss Diagram can be difficult to understand intuitively. Annual energy production is a value related to project finances; Specific Production is the generation per unit of capacity; PR is an overall system performance indicator; the Loss Diagram shows the breakdown of losses; and monthly and hourly results are used to observe seasonal and time-of-day trends. Organizing and explaining them this way makes them easier to understand.

Summary

When reading the results screens in the PVSyst manual, the important thing is not to stop at just the annual energy production. The results screens consolidate the information necessary for design decisions, including energy production, productivity per unit of capacity, system performance, breakdown of losses, seasonal variations, and output trends by time of day.

The first thing to check is the annual generation. This is the entry point for business viability assessment and forms the basis for assumptions about revenue from electricity sales and the benefits of self-consumption. However, because annual generation alone cannot account for differences in system size, it is necessary to use Specific Production to look at generation per unit of capacity.

Next, by checking the Performance Ratio you can understand how efficiently the system is generating electricity under solar irradiance conditions. PR is a comprehensive indicator that includes many losses—such as shading, soiling, temperature, wiring, mismatch, and inverters—and is useful for verifying design quality.

Furthermore, by viewing the Loss Diagram, you can break down the factors behind reduced power generation in detail. By checking whether shading losses are large, temperature losses are large, or the effects of wiring and inverters are significant, you can identify directions for design improvements. Finally, by reviewing monthly and hourly results, you can uncover seasonal patterns or time-of-day anomalies that annual values alone would not reveal.

The PVSyst results screen is both the final review screen for creating reports and a diagnostic screen for improving designs. By checking five points in order—annual energy production, Specific Production, Performance Ratio, Loss Diagram, and monthly/hourly results—you can increase the reliability of the simulation results and produce energy generation forecasts that are easy to explain to stakeholders.