4 Ways to Read a PVSyst Report on One Page | Summary of Key Points

Table of Contents

• Don't try to read the entire PVSyst report from the beginning

• One-page reading method 1: Confirm the conclusions using energy production and PR

• One-page reading method 2: Check major losses in the Loss Diagram

• One-page reading method 3: Verify that input conditions match on-site conditions

• One-page reading method 4: Line up the values to compare and look for anything that seems off

• Items that are particularly easy to overlook in a PVSyst report

• Organizing steps to make it readable on one page

• Judgments to avoid when reading a PVSyst report

• Accuracy improves when combined with on-site verification

• Summary

Don't try to read the entire PVSyst report from the beginning

When reading a PVSyst report, the first thing many people stumble on is the sheer amount of information. It lists various items such as generated energy, PR, irradiance, temperature, array losses, inverter losses, wiring losses, shading, temperature losses, mismatch, IAM, soiling, grid-side losses, and so on. Moreover, because it also includes simulation conditions, module specifications, inverter specifications, azimuth, tilt, meteorological data, and layout conditions, trying to read everything from top to bottom makes it hard to tell what is important.

However, if you establish a way to read PVSyst reports, you can grasp the key points in a short time. In particular, for internal checks, client explanations, reviewing documents for bank submissions, comparing analyses from other companies, and comparing before-and-after design changes, it is more practical to first summarize the key points on a single page than to read all the detailed conditions from the outset.

By "readable on a single sheet" we do not mean that the PVSyst report itself is confined to a single page. It means extracting from the entire report the items necessary for decision-making and arranging generation, PR, major losses, input conditions, and comparison points so they can be read as a single verification sheet.

The purpose of reviewing PVSyst analysis results is not simply to know the annual energy production figure. It is important to verify under what conditions that production was calculated, which losses are significant, whether it conflicts with the design or site conditions, and where it differs compared with other analysis results.

Therefore, when reading a PVSyst report, it is easier to organize your review by looking first at the conclusion, then at the losses, then at the conditions, and finally at the comparisons. Before tracing each detailed item one by one, it is important to grasp the overall picture.

This article explains four methods for reading a PVSyst report at a glance. To make it easier for beginners to avoid getting lost, it organizes which numbers to look at, the order in which to check them, and what kinds of anomalies to watch for.

How to Read on One Page — Method 1: Confirm the Conclusion with Power Generation and PR

When reading a PVSyst report, the first things you should look at are the annual energy production and the PR. Annual energy production shows how much electrical energy the plant is expected to generate in one year. PR stands for Performance Ratio and is an indicator of how efficiently the system converts available solar irradiance and its installed capacity into electrical energy.

If you look only at annual power generation, the figures tend to be larger for bigger power plants, so it can be hard to judge whether the results are good or bad. By looking at the PR, you can check whether the analysis results are within a reasonable range relative to the system size and solar irradiation conditions.

For example, even with the same annual generation of 1,000 MWh, a plant with a small installed capacity and favorable insolation conditions can be rated more highly. Conversely, a plant with a large installed capacity may fall short of expectations. It is important to use annual generation as an indicator of the absolute result and PR as an indicator of the result’s efficiency.

In a PVSyst report, annual energy production, specific yield, and PR are summarized. Specific yield can be viewed as the annual energy production per 1 kWp, and it is useful when comparing projects with different plant capacities. When comparing multiple options with different plant sizes, you should always check specific yield as well as total energy production.

What should be noted here is that a high PR is not necessarily an indication of a good design. PR depends on the settings for solar irradiance and losses. If shading settings are too optimistic, soiling losses are underestimated, wiring losses are set too low, temperature conditions are overly favorable, or output limits are not reflected, PR can appear higher than it actually is.

Conversely, a low PR does not necessarily mean the design is poor. If factors such as snowy regions, highly shaded terrain, sloping sites, long wiring runs, output curtailment, conservatively estimated soiling losses, and conservative temperature losses are correctly reflected, the PR can appear low. The important thing is not to judge by the PR number alone, but to verify the reasons from the loss breakdown.

When organizing on a single page, arranging annual energy generation, specific yield, and PR across the top row makes it easier to read. In internal reviews and client presentations, simply showing these three items first is enough to share the broad outline of the analysis results.

Annual energy production is directly linked to project profitability. Specific yield can be used to compare design proposals and other projects. PR serves as an entry point to check the strictness of analysis conditions and the validity of losses. By looking at these three first, reading the entire PVSyst report becomes much easier.

Especially when comparing multiple PVSyst reports, you need to look not only at differences in annual generation but also at differences in PR and specific yield. This is to distinguish whether the reason for higher generation is simply that the installed capacity is larger, that the irradiation conditions are better, or that the loss settings are smaller.

The first point when reading a PVSyst report at a glance is to grasp the concluding figures first. Before delving into the detailed loss items, check the annual energy production, specific yield, and PR, and get an intuitive sense of whether those results are high or low.

How to Read on One Page — Method 2: Check Major Losses with a Loss Diagram

The next thing to look at is the Loss Diagram. One of the most important pages in a PVSyst report is this loss diagram. By looking at the Loss Diagram, you can see where and how much loss occurs as solar irradiance reaches the module, becomes DC power, is converted to AC power, and is ultimately delivered to the grid.

When reading a PVSyst report at a glance, the Loss Diagram should always be included in the summary. This is because annual energy production or PR alone do not tell you why the results are high or low. By looking at the Loss Diagram, you can determine whether shading losses, temperature losses, inverter losses, or wiring losses are significant.

PVSyst losses are easier to understand if broadly grouped into losses related to solar irradiation, module-side losses, electrical conversion losses, and grid-side losses. Losses related to solar irradiation include near shading, far shading, IAM, soiling, reflection, and the effects of terrain and layout. Module-side losses include temperature losses, low-irradiance losses, mismatch, degradation, and quality variability. Electrical conversion losses include inverter losses, clipping, and MPPT constraints. Grid-side losses include AC wiring losses, transformer losses, and auxiliary equipment losses.

When consolidating onto a single page, you do not need to list every loss in detail. The important thing is to identify, in descending order, the losses that most strongly affect power generation. For example, prioritize calling out items such as significant temperature loss, significant shading loss, significant wiring loss, significant inverter loss, and significant losses due to output limits.

One thing to be careful about in the Loss Diagram is that the basis for loss rates differs by item. Some losses are shown as a percentage of the energy at the previous stage, while others may be expressed relative to the final energy output and therefore may not correspond to the intuitively apparent percentages. For that reason, it is risky to simply add up all the loss percentages and treat that as the total loss. You should understand that PVSyst’s Loss Diagram shows losses step by step along the flow of energy.

One thing beginners particularly tend to overlook is confusing losses that have a large impact on power generation with losses whose numbers simply look conspicuous. Before scrutinizing small loss items in detail, you should first identify and address the major loss items. When explaining differences in annual power generation, it is also easier to explain the causes if you examine the large losses first, in order.

For example, if there is a difference in PR between another company's report and your company's report, comparing the Loss Diagram will show which loss items are different. If the meteorological data are the same but energy production differs, differences in settings for shading, temperature, wiring, inverters, soiling, auxiliary equipment, transformers, etc. can be the cause. Conversely, even if the loss settings are almost the same, if irradiance differs you need to look at differences in meteorological data and site conditions.

When reading a Loss Diagram on a single page, it is important not to simply transcribe the loss items, but to extract only those that are relevant to decision-making. For example, organizing the top five losses, losses that differ significantly from other projects, losses that can be improved by design changes, and losses that require validation against site conditions will make the document easier to read.

If the purpose of reading a PVSyst report is design improvement, the Loss Diagram is used to identify areas for improvement. If shading losses are large, review the layout and spacing; if wiring losses are large, review cable lengths and sizes; if clipping is significant, check the DC/AC ratio and inverter capacity; if temperature losses are large, check the mounting method and ventilation conditions.

On the other hand, in presentations to customers and in materials for banks, the Loss Diagram serves as a means to explain whether the analysis is conservative or not overly optimistic. Demonstrating that loss items have been appropriately included can enhance the reliability of the power generation forecast.

How to Read on One Page 3: Confirm That Input Conditions Match On-site Conditions

PVSyst analysis results can vary greatly depending on the input conditions. Therefore, when reading a report, you need to check not only the energy production and losses but also whether the input conditions match the on-site conditions. No matter how good the reported energy production looks, if the input conditions differ from reality, the analysis results cannot be trusted.

The input conditions to check in a PVSyst report are meteorological data, installation location, azimuth, tilt angle, module specifications, inverter specifications, DC capacity, AC capacity, string configuration, shading conditions, soiling losses, wiring losses, transformer losses, auxiliary equipment losses, and so on. These directly affect the energy yield.

The first thing to check is the meteorological data. PVSyst may use meteorological data such as Meteonorm or SolarGIS. If solar irradiance or temperature change, the annual energy production will change significantly. Especially when comparing multiple analysis results, even for the same location, differences in the meteorological data sources used can be the cause of differences in energy production.

Next are the installation conditions. Azimuth and tilt angle greatly affect power generation. Whether the system is close to south-facing or deviates toward the east or west, and whether the tilt angle is shallow or steep, will change the annual energy output and seasonal generation trends. The items to check also vary depending on the installation method — ground-mounted, roof-mounted, on sloped terrain, or tracking mounts.

Module and inverter specifications are also important. Verify that module capacity, number of modules, temperature coefficient, low-irradiance characteristics, inverter rating, conversion efficiency, number of MPPTs, input voltage range, DC/AC ratio, and other parameters are set correctly. In particular, the relationship between DC capacity and AC capacity should always be checked, as it affects clipping losses and PR.

When reading a PVSyst report on a single page, you don't need to write every input condition in detail. However, you should summarize the key conditions necessary for evaluation. For example, including the location, meteorological data, DC capacity, AC capacity, module model, inverter model, azimuth, tilt angle, soiling loss, wiring loss, and shading conditions on one page makes the assumptions behind the analysis easier to understand.

What's important here is not only to append the input conditions beneath the results, but to read them in conjunction with the results. For example, if the PR is low, check the input conditions to see whether the azimuth or tilt angle is unfavorable, temperature-related losses are large, shading is significant, or wiring losses are substantial. Conversely, if the PR is high, verify whether the loss settings are too small, whether shading is being adequately reflected, and whether the soiling and snow conditions are reasonable.

When checking input conditions, special attention should be paid to omissions in reflecting on-site conditions. Grade differences on the developed site, surrounding trees, buildings, utility poles, slopes, shading between mounting racks, snowfall, vegetation growth, maintenance frequency, PCS placement, cable routes, and so on are elements that are easy to overlook when working from desk-based conditions alone. Even if conditions look clean in PVSyst, they can become loss factors on site.

Also, for reports submitted to banks or used to explain matters to customers, whether the input assumptions are conservative is important. Even if overly optimistic assumptions produce high estimated power generation, large discrepancies from actual results will undermine credibility. Especially for long-term projects, power generation forecasts are directly tied to revenue planning, so reasonable settings that reflect local site conditions are necessary.

When preparing a one-page summary, it is important to view the input conditions as the basis for the results. After reviewing energy production, PR, and losses, verify why those results occurred by checking the input conditions. This enables the PVSyst report to be used not just as a set of calculation results but as documentation for design decisions.

One-Page Reading Method 4: Line Up the Numbers to Be Compared and Notice Any Oddities

PVSyst reports are easier to understand when read in comparison rather than on their own. Having something to compare makes it easier to determine which values are higher or lower, which losses are larger, and which input conditions differ.

Comparisons can include alternative proposals for the same project, previous analyses, competitors' analyses, past projects, measured values, and standard conditions. For example, when comparing layout proposal A with layout proposal B, you can identify where the differences in power generation originate. When comparing with a competitor's analysis, you can infer differences in the input conditions from differences in PR and loss components. When comparing with measured values, you can investigate on-site factors that were not included in the analysis.

To present on a single page, it is effective to arrange the values to be compared side by side. Listing annual energy production, specific yield, PR, solar irradiation, temperature loss, shading loss, soiling loss, wiring loss, inverter loss, AC-side loss, and auxiliary equipment loss makes it easier to see which items are showing differences.

However, when making comparisons, it is important to make the conditions consistent. If the meteorological data are different, the system capacity is different, the azimuth or tilt angles are different, the loss settings are different, or the way output limits are handled is different, comparing only the energy generation will not lead to a correct judgment. First confirm the differences in conditions, and then examine the differences in the results.

Especially in PVSyst reports, large differences in energy production can sometimes actually be caused by differences in solar irradiation. Also, even when differences in PR are small, there can be large differences in annual energy production. This is because PR is an efficiency metric, whereas energy production is influenced by solar irradiation and system capacity.

One of the red flags to look for in comparisons is when the PR is too high. If the PR is extremely high, losses may not have been fully accounted for. You should check whether shading loss, soiling loss, wiring loss, temperature loss, inverter loss, and auxiliary equipment loss are not too small.

Another case is when the PR is too low. When PR is low, there may be design issues, but it can also be due to overly strict condition settings. Verify that excessive shading loss, excessive wiring loss, excessive temperature loss, undersized inverter capacity, or overly restrictive output limitations have not been included.

When you feel that the power generation is too high or too low, first check the annual solar irradiance. If the irradiance is higher compared with other data sources, generation is likely to be higher as well. Conversely, if the irradiance is lower, the generation may appear low even if the loss settings are correct.

Next, examine the differences in loss items. For example, if shading loss is 2 percent in Plan A and 6 percent in Plan B, differences in layout or terrain conditions may be a major cause. If wiring loss is significantly larger in only one case, check differences in cable length, cable size, voltage conditions, and PCS placement.

Furthermore, by examining inverter losses and clipping losses, you can also verify the appropriateness of the DC/AC ratio. If AC capacity is small relative to DC capacity, peak output may be limited and clipping losses may increase. However, designing for a higher DC/AC ratio is not necessarily bad; it should be judged based on a balance with annual energy production and investment efficiency.

What matters in a comparison is being able to explain the differences. It is insufficient to simply state that Option A has higher energy production or that Option B has a lower PR. The practical value of reading a PVSyst report lies in being able to explain why the differences occurred, which conditions influenced them, whether they can be improved through design, or whether they are unavoidable due to site conditions.

When consolidating onto a single page, it becomes easier to understand if you include, for each comparison, the conclusion, major losses, main differences in conditions, and judgment comments. This allows readers of the PVSyst report to understand which points they should check without having to view every detailed page.

Commonly Overlooked Items in PVSyst Reports

When reading a PVSyst report on a single page, you need to pay attention to items that are easy to overlook. Energy production and PR are conspicuous, so many people check them. However, to determine whether the energy production is reasonable, you must check the underlying settings and losses.

One thing that is easy to overlook is differences in meteorological data. Even for the same power plant, annual solar irradiance and temperature vary depending on the meteorological data used. If irradiance changes, generation changes; if temperature changes, temperature-related losses also change. When comparing multiple analysis results, you must always check the type of meteorological data and the site conditions.

Next is soiling loss. Soiling loss may seem like a small item at first glance, but it has an ongoing effect on annual energy production. Appropriate values vary depending on regional rainfall, yellow sand, windblown dust, snowfall, bird droppings, the surrounding environment, and cleaning frequency. If soiling loss is set too low, the estimated energy production will be overly optimistic.

The handling of shadows is also important. In PVSyst, results change depending on the settings for near-field and far-field shading. If shading from surrounding terrain, trees, buildings, or between racks is not correctly included, estimated energy production may appear higher than it actually is. Checking shading conditions is especially important on sloped sites and in complex layouts.

Wiring losses are also easy to overlook. You need to check to what extent losses are accounted for on the DC side, the AC side, and, in some cases, the medium-voltage side. Wiring losses vary depending on cable length, cable cross-sectional area, current, voltage, and PCS placement. Even if the difference looks small in the report, it can be non-negligible in annual power generation.

Auxiliary losses and transformer losses are also items that tend to show differences when comparing reports. Depending on how monitoring devices, air conditioning, PCS auxiliary equipment, transformer no-load losses and load losses, etc. are handled, the final amount of power delivered to the grid will change. It is especially important to confirm how auxiliaries and transformers are treated when the data will be used for bank submissions or long-term profit-and-loss calculations.

Be careful about output limits and power factor conditions as well. The perceived generation and losses can change depending on the PCS's active power limit, apparent power limit, power factor settings, and grid interconnection conditions. Looking only at the results without checking how things are configured in PVSyst can lead to misunderstandings.

Also, in regions with snowfall, it is necessary to confirm how snow is handled. Power generation varies depending on stoppages caused by snow, albedo effects from reflection, winter solar irradiation conditions, and assumptions about snow removal or melting. If snow losses are not included, winter generation may appear higher than the actual.

These items may be scattered across the detailed pages of the PVSyst report. Therefore, a one-page summary sheet should always include not only energy production and PR, but also the key assumptions and loss settings.

Steps to organize content so it can be read on a single page

To read a PVSyst report at a glance, it is important to decide in advance the order in which you will view its contents. The recommended order is: conclusions, losses, conditions, comparisons, comments. Organizing the report in this order allows the reader to grasp the key points in a short time.

First, list the annual energy production, specific yield, and PR. Here, indicate how much generation the analysis expects. When comparing multiple options, list the figures for each option side by side.

Next, extract the major losses from the Loss Diagram. Rather than transcribing every loss in detail, select the large losses that affect energy generation, losses that differ significantly from the comparison, and losses that are important for decision-making. In particular, shading, temperature, soiling, wiring, inverters, auxiliary equipment, transformers, and output limitations are items that are commonly checked.

Next, we will organize the input conditions. We will list the location, meteorological data, DC capacity, AC capacity, azimuth, tilt angle, modules, inverters, string configuration, shading settings, soiling losses, wiring losses, and so on. This will make the assumptions behind the results clear.

If comparisons are required, clearly state the differences. Verify differences from the previous analysis, from other companies' analyses, between design proposals, and from measured values. If discrepancies appear, comment on which conditions or losses are likely causing them.

Finally, write an assessment comment. For example: the power generation appears to be within a reasonable range; because the PR is high, check the shading and soiling settings; because wiring losses are large, recheck the cable conditions; the difference in solar irradiance is considered to be the main cause of the power generation difference.

Organizing it this way lets readers of the PVSyst report know where to look without checking every detailed page. Especially for meeting materials or client presentations, it is efficient to present the key points on a single page and, if necessary, refer to the detailed PVSyst report.

Judgments to avoid when reading PVSyst reports

When reading a PVSyst report, what you should avoid is judging performance solely by energy production. Energy production is an important indicator, but it is influenced by system capacity, irradiance, loss settings, output limitations, and site conditions. It is risky to simply conclude that high energy production is good and low energy production is bad.

Also, you should avoid making judgments based solely on PR. PR is a useful metric, but how it appears changes depending on the analysis conditions. If the loss configuration is lenient, PR will be higher; if it is strict, PR will be lower. PR should be viewed as an entry point to the results, and the final judgment needs to be made together with the loss composition and the input conditions.

You should also avoid simply adding the loss rates in the Loss Diagram. Because PVSyst calculates losses stepwise, summing the displayed percentages and treating them as the overall loss can be misleading. It is important to follow the energy flow to see what is being reduced at each stage.

Furthermore, when comparing reports from other companies, you should avoid evaluating differences without first aligning the conditions. If weather data, installed capacity, azimuth, tilt, loss settings, output limits, or the treatment of auxiliary equipment and transformers differ, it is only natural that the results will differ. When making comparisons, first check for differences in conditions, and then look at differences in generation and PR.

Accuracy improves when combined with on-site verification

The PVSyst report is the result of a desk-based analysis. Therefore, when read in conjunction with on-site conditions, it enables more practical decision-making. Shadows, terrain, nearby obstacles, cable routes, construction status, snowfall, soiling, and vegetation growth—factors that cannot be determined from drawings or aerial photographs alone—need to be supplemented by an on-site inspection.

In particular, it is important that the shading losses and wiring losses shown in the report are consistent with the actual site conditions. Actual losses vary depending on the racking layout, the location of the PCS, the position of junction boxes, cable routes, and the presence or absence of surrounding structures. Even if PVSyst is configured under ideal conditions, there may be different constraints on site.

In recent years, combining smartphones, GNSS, point clouds, and AR can improve the efficiency of on-site verification. For example, using a system that combines an iPhone with a high-precision GNSS, like LRTK, makes it easier to accurately determine site positions while checking consistency with drawings and survey data. For design and construction verification of solar power plants, linking desktop PVSyst analysis with on-site positional information can improve the accuracy of checks for shading, layout, site grading, and equipment locations.

Comparing the PVSyst report with on-site conditions, rather than relying on the report alone, is important for improving the reliability of generation forecasts. If the analysis results seem questionable, you should not judge solely by the figures in the report but return to verify them against the actual site conditions.

Summary

PVSyst reports contain a large amount of information, so if you try to read everything from the start you can easily lose sight of the important points. In practice, it is effective to organize annual energy production, specific yield, PR, major losses, input conditions, and comparison points on one page and read them.

First, confirm the conclusion based on annual energy production and PR. Next, check for major losses in the Loss Diagram. Then, verify input conditions such as meteorological data, system capacity, azimuth, tilt angle, modules, inverters, wiring, soiling, and shading. Finally, compare with other proposals, other companies' analyses, and measured values to see where the differences lie.

When reading a PVSyst report, the important thing is not to take the figures at face value, but to be able to explain why those figures are what they are. If you can organize the reasons why energy production is high or low, why the PR changes, and why losses are large, the PVSyst report becomes a practical resource for design decisions and for explaining results to customers.

The key points for reading on a single page are four: conclusion, losses, conditions, and comparisons. If you organize information in this order, even detailed PVSyst reports become easy to understand in a short time. The basic rule for correctly reading a PVSyst report is to not judge based only on energy production, but to check the loss breakdown and the input conditions as well.