5 Ways to Read PVSyst Result Tables | Where Should You Look?

In practical work on solar power system design and generation forecasting, there are many situations where knowing how to read the output tables is more important than running the simulation itself. Even if you prepare the input conditions properly, if you do not know which parts of the output tables to look at, the validity of the design, the accuracy of comparisons, and the persuasiveness of explanations both inside and outside the company will not improve. Especially for practitioners searching for "how to read PVSyst", when faced with output tables full of numbers they are likely to be unsure which items to look at first.

In practice, the results table lists many seemingly important figures such as annual energy production, specific yield, PR, solar irradiation, losses, monthly values, and grid-side energy. For that reason, if you are not familiar with it, you tend to pick out only the numbers that catch your eye and make judgments. However, the results table is not merely a list of numbers. It is a document that organizes, in tabular form, a sequence connecting site conditions, installation conditions, incident light conditions, losses, the DC-side status, and the AC-side status. That is why having an order in which to view it is very important.

For example, a reading that stops at looking only at the annual energy production reveals almost nothing about the background of the results. Conversely, if you first examine loss items in detail, you will misjudge their relative importance unless you understand the underlying solar irradiance and incident conditions. To use the results table correctly, you need to grasp the overall picture first and then dig into the causes. In other words, the order in which you look is as important as what you look at.

In this article, I summarize the five key ways of reading PVSyst result tables that practitioners should grasp first. Rather than simply following the field names on screens and reports, I focus on which numbers to look at and for what purpose to make judgment easier. Ultimately, I present the material in a practical format, including the point that reading the numbers in the result tables is linked to accurately understanding the on-site spatial relationships.

Table of Contents

• Key concepts to keep in mind before reading the results table

• How to read 1｜First, look at the overall picture using annual generation and specific yield

• How to read 2｜Next, check the solar irradiation and incident light conditions

• How to read 3｜Interpret causes from PR and loss items

• How to read 4｜Look at monthly results to see seasonal variations and anomalies

• How to read 5｜Finally, look at the numbers for the grid side and the self-consumption side

• Common misinterpretations when reading the results table

• Organize which items to check in practice according to the objective

• The accuracy of on-site conditions influences how convincing the results table is

• Summary

Key concepts to understand before reading the results table

When reading the PVSyst results table, the first thing to understand is that the numbers listed there are not independent. Solar irradiance occurs at a location, that irradiance reaches the installation surface, is converted into electrical power while being affected by incident-light conditions, shading, temperature, and other factors, is then converted from the DC side to the AC side, and ultimately results in the energy yield and grid injection. The results table lays out this entire sequence as numerical values. Therefore, each number has a contextual relationship with the others.

If you ignore the surrounding context, the results table quickly becomes difficult to understand. Looking only at annual generation, you cannot tell why that value was reached. Looking only at PR, you cannot see which losses are having an effect. Even if you look only at the loss items, it is hard to judge whether a loss is significant or minor unless you know the underlying solar irradiance and incident light conditions. To make effective use of the results table, you need to view the numbers not as isolated points but as a flow.

It is also important to consider that results tables are not documents that show the definitive answer, but materials that provide input for decision-making. In practice especially, it is dangerous to treat the numbers in a results table as if they were correct as-is. This is because the figures shown there depend on the input conditions and the model’s assumptions. The numbers in the results table will change depending on the location settings, orientation, tilt, shading conditions, equipment configuration, and how the demand profile is defined. In other words, a results table is merely an aggregation of the underlying assumptions.

Therefore, the basic order for reading is: first grasp the overall picture using the rough numbers; next check the solar irradiation and incident light conditions; then dig into the reasons using losses and monthly results; and finally look at the final output figures related to feed-in and self-consumption. Having this order makes it easier even for beginners to understand "where they are looking now" and prevents them from being overwhelmed by the numbers. To read result tables consistently, it is important to learn this flow before memorizing individual items.

How to Read 1｜First, view the overall picture by looking at annual electricity generation and specific yield

When you open the results table, the first thing you want to see is the annual power generation. This is the clearest figure for grasping the overall scale of a project. By checking up front how much generation can be expected, you can get a rough sense of the project's position. In internal briefings and when giving an overview to clients, this number is often the entry point.

However, you must not end your evaluation based solely on annual power generation. This is because annual power generation directly reflects differences in installed capacity and site conditions. Projects with larger capacity tend to have higher annual generation, and figures naturally tend to be higher in regions with better solar irradiation. Therefore, while annual power generation is a figure you should look at first, it alone does not determine the quality of a project.

So what we want to look at together is specific power generation. By looking at specific power generation, it becomes easier to understand how much electricity is being generated per unit of installed capacity. If annual generation is a figure of scale, specific power generation is a figure that captures a sense of performance. For example, even if there is a difference in annual generation between two projects, the difference may not be that large when viewed in terms of specific power generation. In that case, the difference in annual figures may be mainly due to differences in scale or site conditions, and may not indicate a difference in the quality of the design.

In practice, the reason for looking at these two metrics first is that they show where in the results table you should dig deeper. If the annual energy production is sufficiently high but the specific yield is not improving, the project may have scale but be lacking in performance. Conversely, if the annual energy production is not that large but the specific yield is stable, it becomes easier to conclude that the design is well put together even under challenging conditions. The first step is to put annual energy production and specific yield side by side and grasp the overall outline of the project.

How to Read 2｜Next, Check Solar Radiation and Light-Receiving Conditions

Once you have grasped the overall picture from annual generation and specific yield, the next things to check are solar irradiation and the light-receiving conditions. This is the work of examining the foundation of the generation results. If you only look at how much power is being generated, you cannot fully interpret the figures unless you know how much solar irradiation the site receives and how well the installation surface is capturing that irradiation.

First, what you should check is site conditions such as solar irradiation on a horizontal plane. This indicates how much solar resource the project originally has. If a site has favorable irradiation conditions, the annual energy output will tend to be higher; conversely, if a site has poor irradiation conditions, no matter how much you optimize the design, the upper limit of what can be achieved is to some extent fixed. Therefore, when viewing the results table, it is important to understand those underlying irradiation conditions before looking at the final energy output.

Next to check are the irradiance conditions—how much solar radiation a tilted surface receives. Even at the same location, the amount of solar radiation received by the equipment varies depending on the azimuth and tilt settings. In other words, even if the site conditions are the same, different installation conditions will change the power output. By looking at the solar radiation–related items in the results table, the connection between site conditions and installation conditions becomes easier to understand.

Viewed in this order, you get a much clearer sense of the annual power generation and specific yield figures. It becomes easier to separate whether a high annual generation is due to inherently strong solar irradiation at the site or to efficient installation conditions. Conversely, if the solar irradiation is not poor but the results are not high, you should turn your attention to the incident light conditions and the loss structure. Checking the solar irradiation and the incident light conditions early when reading the results table also prepares you to interpret the losses later.

Reading method 3｜Inferring causes from PR and loss items

Next, you should look at PR and the loss items. This is the first point where you begin to read into the reasons why those results occurred. PR is a number that often attracts attention in results tables; it’s easiest to understand if you think of it as a single value that makes the overall cohesion of the system easy to see. However, if you judge only by whether PR is high or low, the background will be obscured. That is why the loss items are necessary.

In the results table, the loss items list various factors such as shading, temperature, mismatch, wiring, and conversion. The important point here is not to treat all losses as having the same weight. Losses that reduce received light in an earlier stage are fundamentally different from losses that reduce AC output in a later stage. Losses related to shading and incident-light conditions reduce the baseline, while wiring and conversion losses eat into the energy that remains afterward. For this reason, when examining loss items it is necessary to be aware at which stage the loss is taking effect.

To make PR a practical, usable metric, it's important to always return to the loss components after looking at PR. If PR is high, verify why by checking which losses are small. If PR isn't improving, look at which losses are dragging it down. By doing this, PR becomes not just an evaluation score but an entry point for interpreting the losses. This is the approach that is useful in practice.

Also, because the results table lists many small loss rates, beginners tend to focus only on the items with large numbers. However, large does not necessarily mean important. If you don't consider whether a loss can be reduced or should be accepted, you'll misprioritize in practice. By looking at PR together with the loss items, the meaning of the numbers becomes much more concrete.

Interpretation 4｜Check Monthly Results for Seasonal Differences and Anomalies

When reading result tables, beginners tend to overlook the monthly results. However, in practice, the monthly results are very important. Seasonal differences and anomalies that cannot be seen from annual totals become quite clear when viewed month by month. Annual power generation and PR are useful as overall summaries, but the monthly results show the details.

The first thing to check is the shape of the peaks and valleys. We look at which seasons see increases in power generation and which seasons see declines. This reveals whether shading effects are concentrated in winter, temperature effects are impacting performance in summer, or whether the output is stable overall. If you only look at annual figures, a project may appear "reasonably good," but on a monthly basis there can be significant weaknesses in specific seasons.

Monthly results are also useful for noticing inconsistencies in the input conditions. If summer generation does not increase as expected given the solar irradiation conditions, you should suspect temperature effects or downstream losses. If the winter drop is unusually large, check for shading or orientation conditions. In other words, monthly results serve as a checkpoint for verifying the consistency of the entire results table.

In practice, monthly results are useful when explaining to customers or internal stakeholders. Even if annual power generation alone is abstract, showing monthly trends makes it easier to convey when a project is strong and when caution is needed. As a way of reading the results table, simply having the habit of checking the monthly breakdown at the end will allow you to understand the meaning of the annual figures much more deeply.

How to Read 5 | Finally check the numbers on the grid side and the self-consumption side

What you want to see at the end of the results table are the figures for the grid side and the self-consumption side. By "grid side" here I mean the figure for how much electricity was ultimately sent to the grid. For self-consumption projects, the figures for how much was used on the demand side and how much was supplied by the grid are also important. In other words, this is the stage of looking not only at the amount generated but at how that electricity was ultimately used.

For projects focused on selling power, the figures for the amount of electricity sent to the grid tend to directly influence business decisions. By looking at the difference between generated output and the amount injected into the grid, it becomes easier to understand the impact of downstream losses and equipment configuration. For self-consumption projects, examining the user's demand, the portion of that demand met by solar, and the amount drawn from the grid to cover the shortfall makes it easier to assess the viability of self-consumption.

The reason to look at this last, in this order, is that the figures for the grid side and for self-consumption are close to the final result. If you look at this section alone first, you won't understand why those numbers were reached. However, if you first look at annual generation, solar irradiation conditions, incident light conditions, PR, losses, and the monthly results, it becomes easier to give meaning to these output figures. In other words, when reading the results table, it's clearer to view the output figures last.

In practice, figures such as the amount of electricity sold or self-consumed are very easy to explain, so people tend to focus on them first. However, if you use the results table correctly, those figures are conclusions rather than starting points. It is important to accept those numbers as the outcome of the flow you have read up to this point.

Common Misreadings in Result Tables

One common misreading of result tables is evaluating a project solely by its annual energy production. Annual energy production is easy to understand, but it is a figure that mixes site conditions, plant scale, and loss structure. Therefore, if you judge the quality of a design by that alone, you will not be able to isolate the causes.

Another common tendency is to treat PR as a universal evaluation metric. PR is useful, but its significance becomes shallow if you don’t look at the context behind it. If you judge based only on PR without considering solar irradiance conditions and loss factors, you are likely to be swayed by the superficial numbers.

Moreover, treating all loss components as equally significant is dangerous. Losses occurring near the light-receiving stage and those from downstream wiring or conversion require different mitigation approaches and carry different weights. When reading the results table, it is important to be mindful of the stage at which each loss occurs.

Moreover, it is a common mistake to conclude an explanation based only on annual values without checking the monthly results. Biases or anomalies that are not visible in the annual figures can become clear in the monthly data. The results table can only be used effectively by reading it back and forth between the annual and monthly values.

Organize what to look for in practice by purpose

How to read the results table shifts slightly depending on the practical purpose. For example, in the initial comparison of projects it can be sufficient to grasp the overall picture from the annual energy production and specific yield, and to judge rough relative strengths and weaknesses from PR and the main losses; at this stage it is more important to quickly understand where a project stands than to dig into details.

On the other hand, during detailed design and review stages, it is necessary to carefully examine solar radiation conditions, incident-light conditions, loss items, and monthly results. In particular, it is important to determine in which seasons the effects of shading and temperature are most pronounced, and which losses have room for improvement. The result tables should be used as materials for identifying parts of the design that need to be revised.

In customer explanations, it's easier for clients to understand if you show not only the annual power generation but also monthly trends and figures closer to actual electricity sales and self-consumption. However, if the underlying solar irradiance conditions and losses haven't been clarified, the explanation will remain superficial. Ultimately, in practice and for any purpose, the foundation is being able to read result tables as a coherent flow.

In short, where you should look changes depending on your purpose, but the underlying order in which you read remains the same. If you keep the sequence—first the overall picture, then the foundation, then the causes, and finally the exit—you’ll be less likely to get lost even when you shift your emphasis according to each objective.

The accuracy of on-site conditions affects the credibility of the results table

The result table is just numbers on a screen, but how convincing they are depends heavily on the accuracy of the understanding of on-site conditions. In particular, shadows, orientation, tilt, the positional relationship with obstacles, equipment layout, and cable routes directly affect the figures in the result table. In other words, correctly reading the result table requires an understanding of the site as a prerequisite.

For example, when shading losses are large, to distinguish whether they truly originate on site or whether the 3D conditions or layout inputs are lax, you need to have an accurate grasp of the on-site spatial relationships. AC-side losses, too—if the sense of distance to the board or the injection point is vague, the validity of the numbers in the results table is weakened. Whether the figures in the results table are convincing depends on the realism of the inputs.

In this sense, having a means to grasp the on-site positional relationships with high accuracy is also linked to how you read the results tables. If you can confirm equipment positions, obstacle positions, orientation, and spacing with high precision, it becomes easier to organize the assumptions to enter into PVSyst, and you will have greater confidence in the figures in the results tables. The ability to read results tables and the ability to grasp the site are not separate.

From that perspective, it naturally leads to LRTK, an iPhone-mounted GNSS high-precision positioning device. By making on-site position checks, distance assessments to obstacles, and orientation organization easier to carry out with high accuracy, it becomes easier to tighten the assumptions related to shadows and placement. In practical work where you want results that are convincing not just by staring at the numbers in a results table but also by including those underlying assumptions, measures like LRTK are effective.

Summary

When reading PVSyst result tables, it is easy to follow a five-step sequence: first grasp the overall picture from the annual energy production and specific yield, next confirm the foundation with solar irradiation and incidence/illumination conditions, then identify causes from the PR and loss items, check seasonal differences and any anomalies in the monthly results, and finally look at the output figures on the grid side and the self-consumption side. Simply having this flow makes it much clearer where to look in the result tables.

What matters is reading the results table not as a list of numbers but as a document that depicts the flow of power generation. Looking at it in the order of the overall picture, the foundation, the causes, and the outputs brings even beginners closer to a way of reading that can be used in practice. Understanding the numbers in the results table is not simply knowing the figures, but being able to explain why those figures came about.

And to further enhance that explanatory power, it is essential to grasp the positional relationships on site with high precision. If you want to organize shadows and layout conditions more accurately, it can be useful to consider using the LRTK, an iPhone-mounted GNSS high-precision positioning device. By combining the ability to correctly read result tables with the ability to accurately understand the site, it becomes easier to arrive at more convincing design decisions and power generation forecasts.