5 Tips to Learn How to Read PVSyst in the Shortest Time

Table of Contents

• Read PVSyst by following the overall flow rather than focusing on details

• Tip 1: Don't judge based solely on energy production figures

• Tip 2: Use the Loss Diagram to see where losses occur

• Tip 3: Read PR not in isolation but together with the conditions

• Tip 4: Check meteorological data and design conditions first

• Tip 5: When comparing, make sure to align the same assumptions

• Practical, hands-on way to read PVSyst to learn it as quickly as possible

• Summary

Approach PVSyst by focusing on the overall flow rather than the details

When you see a PVSyst report for the first time, many people initially turn their attention to the annual energy production and PR figures. Of course, annual energy production and PR are important. However, to learn how to read PVSyst in the shortest time, it is more important to grasp the overall flow first rather than start by chasing each detailed loss item one by one.

PVSyst is simulation software for calculating the electricity production of photovoltaic power plants. Based on input meteorological data, modules, PCS, azimuth and tilt angles, shading, wiring losses, temperature losses, soiling, degradation, output limits, and other factors, it estimates the final energy production. In other words, the generation figures shown in the report are not merely a single calculation result but the final values after applying numerous assumptions and loss calculations.

Therefore, when reading PVSyst, you must first check “under what conditions the results were calculated.” Before judging whether the generation is high or low, confirm that the plant’s location, solar irradiance, temperature, installed capacity, PCS capacity, azimuth, tilt, treatment of shading, and loss settings are reasonable. If you skip this and look only at the generation figures, you may mistakenly interpret the results as good or bad when in fact the conditions are simply different.

The quickest way to learn how to read it is to view a PVSyst report not as a "results table" but as a document that shows how energy is reduced as it becomes the final generated output. Sunlight strikes the panel surface, becomes DC power in the module, travels through the wiring, is converted to AC by the PCS, and is ultimately transmitted to the grid. If you keep this flow in mind, the meaning of each page and each item will start to make sense.

Many of the reasons people get confused when reading PVSyst stem from looking at numbers in isolation.

For example, even if the PR is low, its meaning changes completely depending on whether the cause is large temperature losses in a region with high solar irradiance, significant shading losses, substantial clipping from PCS oversizing, or large wiring losses. The same PR can point to different areas that need improvement depending on the underlying cause.

In short, to learn PVSyst as quickly as possible, it is important to fix the order in which you first look at things. If you view them in the order of generated energy, irradiation, PR, Loss Diagram, main losses, input conditions, and comparison conditions, it becomes easier to understand the overall structure of the report.

Tip 1: Don't judge solely by the power generation figures

The most common mistake when interpreting PVSyst is evaluating it based solely on annual energy production. Annual energy production is an important figure that indicates the final output, but you cannot judge the quality of a design by that alone. This is because energy production is heavily influenced by the size of the power plant.

For example, even if a power plant has high annual generation, it may simply have a large DC capacity. Conversely, a plant that appears to have low annual generation may actually have a high generation per unit of installed capacity. Therefore, when looking at generation figures, you should always check them in relation to installed capacity.

In practice, it is easier to make assessments by looking at the annual specific yield—the annual energy generation divided by DC capacity—i.e., an indicator such as kWh/kWp. This value allows you to normalize, to some extent, for differences in power plant size and compare them. Furthermore, by taking into account regional solar irradiation conditions, snow cover, temperature, tilt angle, and azimuth, you can more accurately assess the plausibility of the generation output.

Also in PVSyst, not only the energy yield results but also which solar radiation dataset is used is extremely important. Even with the same system specifications, the energy yield can change significantly if the meteorological data differ. Depending on which data are used—Meteonorm, SolarGIS, nearby observational data, or custom-corrected data—the annual solar radiation and monthly trends may vary.

If the power generation is higher than expected, first check whether the solar irradiance is too high. If the power generation is lower than expected, check whether the solar irradiance is too low or whether shading or other losses are excessively affecting it. Rather than judging 'good' or 'bad' only by the power generation, it is important to verify the assumptions that led to that generation.

When reading PVSyst, it's fine to first look at the annual energy production. However, immediately afterward, check "for which capacity this production figure applies," "which meteorological data it is based on," and "what losses it has passed through." Simply forming this habit will greatly reduce misreadings of PVSyst.

Energy production is the final result, not the cause. The quickest way to understand PVSyst is to treat energy production as the starting point and then trace back to check the underlying conditions.

Tip 2: Check where the loss is decreasing in the Loss Diagram

One of the most important pages for learning how to read PVSyst is the Loss Diagram. The Loss Diagram is a figure that shows, step by step, where and by how much solar energy is reduced before it becomes the final AC output. If you want to understand PVSyst as quickly as possible, being able to read this Loss Diagram is the quickest way.

In the Loss Diagram, horizontal-plane irradiance and tilted-plane irradiance are displayed first. From there, through near-field shading, far-field shading, IAM losses, soiling losses, and so on, the effective irradiance entering the module is determined. After that, module temperature losses, low-irradiance losses, mismatch losses, wiring losses, PCS losses, output limiting, and so on are sequentially applied, bringing the result closer to the final generation at the grid interconnection point.

Understanding this flow makes it easier to identify the causes of low power generation. For example, if temperature losses are large, you need to check the local ambient temperature, the mounting structure type, ventilation conditions, and the heat dissipation conditions on the back of the modules. If shading losses are large, check the terrain, adjacent rows, surrounding obstacles, array spacing, and 3D scene settings. If wiring losses are large, check cable length, conductor cross-sectional area, current, voltage, and the DC-side and AC-side settings.

What is important in a Loss Diagram is not just looking at items with large loss rates, but understanding at which stage the losses occur. Whether the losses occur before sunlight reaches the module, on the DC side after the module has generated power, or on the AC side after the PCS, the appropriate countermeasures differ.

Also, the figures in the Loss Diagram do not simply add up to give the total loss. Each loss is calculated step by step, with the next loss applied to the result of the previous stage. For that reason, the way loss rates appear and the reference basis can differ from item to item. When you are not yet familiar with reading PVSyst, it is important to read the values with an awareness of “which reference the loss rate is relative to.”

Even when reviewing comparison reports, the Loss Diagram is extremely useful. If annual energy production differs between your company's analysis and another company's analysis, the first thing to look at is not the difference in final energy output but where on the Loss Diagram the difference is being generated. Breaking down whether the difference is due to solar irradiance, shading losses, temperature losses, or PCS losses makes discussion much easier.

To learn PVSyst as quickly as possible, read the Loss Diagram not as a "list of losses" but as the "calculation pathway" by which the energy output is generated. Once you can follow the flow to the final energy output, your understanding of the entire report will rapidly improve.

Tip 3 Read PRs together with the conditions, not in isolation

In PVSyst reports, PR is often highlighted. PR stands for Performance Ratio and is a representative indicator of the performance of a solar power generation system. Simply put, it is a value that shows how effectively the system actually generates electricity compared to the theoretically obtainable energy.

However, PR is not a number that can be used on its own to judge whether something is good or bad. You cannot simply say that a high PR indicates a superior design or that a low PR indicates an inferior design. PR is influenced by weather conditions, temperature conditions, loss settings, PCS capacity, output limits, snow, shading, soiling, degradation, wiring conditions, etc.

For example, in cold regions temperature losses tend to be smaller, so PR can appear higher. Conversely, in hot regions temperature losses tend to be larger, so PR can appear lower. In snowy regions, PR varies depending on how winter solar radiation and snow losses are treated. In other words, PR is strongly influenced not only by the plant’s design but also by site conditions.

The PCS capacity setting also affects the PR. If the PCS capacity is small relative to the DC capacity, output can become capped during periods of strong solar irradiance, causing clipping losses. In such cases, designers may intentionally increase the DC capacity to maximize annual energy production, but this can reduce the PR. If one looks only at PR, economically rational oversized designs may be judged unfavorably.

Also, in PVSyst the PR changes depending on how the loss settings are entered. Wiring losses, module quality losses, mismatch losses, LID, ageing/degradation, PCS efficiency, transformer losses, auxiliary losses, etc.—the results vary depending on which losses are included. Therefore, when comparing PRs you must confirm that you are comparing the same range of losses.

To learn PVSyst as quickly as possible, view PR not as a "single report card" but as a "conditional efficiency metric." If PR is high, check why it is high. If PR is low, check which losses are affecting it. Do not draw conclusions based solely on the PR number; it is important to assess it together with the Loss Diagram and the input conditions.

In practice, when reviewing PR, checking annual energy production, specific yield, solar irradiation, temperature losses, PCS clipping, and wiring losses at the same time improves the accuracy of your assessment. PR is important, but approaching the data with the premise that PR alone cannot explain many aspects is the quickest way to properly understand PVSyst.

Tip 4 Confirm meteorological data and design conditions first

When reading PVSyst results, it's easy to focus on the loss items, but in fact there are things you should check first. Those are the meteorological data and the design conditions. PVSyst's energy production depends heavily on the input conditions. If the inputs change, the results will of course change as well.

In meteorological data, we check annual solar radiation, monthly solar radiation, temperature, wind speed, and so on. Particularly important is whether the meteorological data are appropriate for the power plant's location. If the site is offset, the elevation is substantially different, coastal and inland climates differ, or snow conditions are not reflected, the estimated power generation can vary greatly.

Monthly trends are also important. Even if the annual solar irradiation is about the same, generation characteristics differ between regions with more irradiation in summer and those with more in winter. When irradiation is concentrated in high-temperature periods, temperature losses tend to be larger, and when irradiation is greater in cold periods, PR may appear relatively high. In snowy regions, it is also necessary to check whether winter generation and loss settings are appropriate.

In the design conditions, check module capacity, PCS capacity, DC/AC ratio, azimuth, tilt angle, array configuration, string configuration, shading settings, terrain, racking spacing, and so on. In PVSyst, results can change even if these conditions differ only slightly. Especially when comparing multiple proposals, you must confirm that the design conditions are the same; otherwise, the comparison will not be valid.

For example, if a report shows high energy production, it may simply be because the azimuth or tilt angle are set favorably. If another report shows low energy production, it may be because shading has been modeled more conservatively. Which is correct needs to be determined in light of the site conditions and the design intent.

To learn PVSyst as quickly as possible, it is important to develop the habit of "reading the input conditions" before looking at the results. When something feels off about the energy generation or PR, rather than immediately digging into the loss items, first check the weather data and design conditions. If the input conditions are different, it is only natural that the results will differ.

If you follow this order, the way you read PVSyst becomes more consistent. First, look at the site location and meteorological data. Next, check the system capacity and PCS capacity. Then look at the azimuth, tilt angle, shading, and loss settings. After that, review the annual energy production and PR. Reading in this sequence clarifies the meaning of the numbers.

Tip 5: Use the same assumptions when comparing

PVSyst is often used not only to read a single report but also to compare multiple scenarios. For example, when changing the racking angle, PCS capacity, module type, shading settings, or loss rates. Also, multiple PVSyst reports are sometimes compared among project developers, design firms, third‑party agencies, and financial institutions.

What matters most is to standardize the comparison conditions. PVSyst results can easily change depending on differences in input conditions; if the weather data are different, the capacity is different, the loss settings are different, the way shading is treated is different, the way degradation is applied is different, or the handling of output control is different, then simply comparing energy generation or PR is of little meaning.

When comparing, first separate and organize the conditions that are the same and those that differ. Check the power plant location, meteorological data, DC capacity, PCS capacity, modules, PCS, azimuth, tilt angle, loss settings, shading settings, transformers, auxiliary losses, output limits, and so on. Then examine where the differences in power generation originate.

For example, when there is a difference in power generation, we break down whether that difference is due to differences in solar irradiance, differences in design capacity, or differences in loss settings. It is especially important not to conflate differences in solar irradiance with differences in loss rates. If the solar irradiance is different, power generation will change even with the same design. If the loss settings are different, power generation will change even with the same solar irradiance.

When making comparisons, it is risky to look only at PR. Even if PR is the same, annual energy generation can differ, and even if annual energy generation is the same, PR can differ. This is because solar irradiation conditions, installed capacity, and loss composition are different. The indicators you should examine also vary depending on whether the purpose of the comparison is a business feasibility assessment, design improvement, or a third-party review.

To learn PVSyst as quickly as possible, it's helpful to fix the axes when creating comparison tables. Lining up annual energy production, specific yield, PR, annual irradiation, temperature losses, shading losses, IAM losses, soiling losses, wiring losses, PCS losses, and clipping losses makes it easier to see the causes of the differences. You don't need to examine every item in detail, but it's important to identify the main factors causing the differences.

The purpose of comparison is not to decide by intuition which figure is correct. It is to clarify which assumptions differ and how much those differences affect the results. With this way of thinking, comparing PVSyst reports becomes much easier to read.

Practical Study Method to Learn PVSyst in the Shortest Time

If you want to learn how to read PVSyst in the shortest possible time, you don't need to try to memorize every item perfectly. What matters in practice is being able to decide where to check when you look at a report.

The first thing to check is the assumptions of the simulation. Confirm the power plant’s location, meteorological data, installed capacity, modules, PCS, azimuth, and tilt angles. If there are major inconsistencies at this stage, it is of little use to scrutinize the subsequent power output or PR in detail.

Next, review the annual generation and specific yield. By looking not only at total generation but also at generation per unit of capacity, you can adjust for differences in plant size when evaluating. Additionally, examining monthly generation makes it easier to notice seasonal characteristics and anomalies.

Next, check the PR. If the PR is higher or lower than what is generally expected, do not draw immediate conclusions; return to the Loss Diagram. Any discrepancy in PR should be broken down and checked for temperature loss, shading loss, soiling loss, wiring loss, PCS loss, clipping loss, etc.

In the Loss Diagram, check the loss components in order from the largest. However, even components with small loss rates warrant attention if their assumptions are unrealistic. For example, if the wiring loss is extremely low, verify that the cable length and cross-sectional area settings are realistic. If there is almost no shading loss, check that terrain and surrounding obstructions have been properly included.

Finally, when there are items to compare, clarify the differences in conditions. When comparing PVSyst results, it is important to look not only at differences in outcomes but also at differences in assumptions. If you can explain why the energy production differs, you will be close to a practical, professional level in reading the report.

The shortcut to learning PVSyst is to read it in the same order every time. Even if it takes longer at first, by checking the same sequence repeatedly you will naturally begin to notice numbers that feel off. For example, it becomes easier to judge when temperature losses are too large, wiring losses are too small, PCS clipping is larger than expected, or PR is too high for the conditions.

Also, PVSyst results are influenced by on-site construction and survey information. Even if the design assumes minimal shading, actual terrain, surrounding structures, racking positions, or construction tolerances can change the outcomes. Therefore, in addition to desk-based simulations, combining on-site inspections, positioning data, drawings, and point cloud data will enable a more realistic assessment.

Combining a mechanism that leverages an iPhone and GNSS, like LRTK, to verify on-site position information and as-built conditions makes it easier to check differences between design conditions and actual site conditions. PVSyst is a powerful tool for evaluating power generation, but the higher the accuracy of the underlying on-site information, the easier it is to enhance the reliability of the simulation results.

Summary

To learn how to read PVSyst as quickly as possible, it's more important to establish a fixed reading order than to memorize detailed terms one by one. First, don't judge based solely on energy production; check the meteorological data, system capacity, and design conditions. Next, use the Loss Diagram to follow the flow from solar irradiation to the final energy production. Then, interpret PR not in isolation but together with the loss conditions and site conditions.

PVSyst is not just software for producing a final energy yield. It is also a document for checking which assumptions were made, which losses were anticipated, and how generation is expected to decline. Therefore, when reading the report, it is important not only to look at the magnitude of the numbers but to examine the reasons those numbers were produced.

The tip for learning in the shortest time is to review in the order of annual energy production, specific yield, PR, Loss Diagram, meteorological data, design conditions, and comparison conditions. If you make this order a habit, when you look at a PVSyst report it will be easier to see what is important and what should be examined more deeply.

When power output is high or low, do not draw immediate conclusions; break it down and check solar irradiance, temperature losses, shading losses, wiring losses, PCS losses, clipping losses, etc. When making comparisons, always confirm that they are being compared under the same assumptions. If you compare only the results when the assumptions differ, you may make an incorrect judgment.

Reading PVSyst gets faster the more you use it. Even if it seems difficult at first, once you understand the flow of energy and the order of losses, it becomes easier to grasp the meaning of the entire report. The basics are the same in every situation: design, feasibility assessment, third‑party review, documents submitted to banks, explanations of differences in power generation, and so on.

The ability to correctly interpret PVSyst is important for improving the decision-making accuracy of solar power projects. Furthermore, by combining it with on-site surveys, drawing checks, and post-construction as-built inspections, you can grasp the differences between the simulation and the field more concretely. Incorporating on-site verification using LRTK, GNSS positioning, and cross-checking with drawings can bring PVSyst’s assumptions closer to actual site conditions and help improve the reliability of power generation estimates.