10 Tips for Reading PVSyst Reports｜Organized for Beginners

PVSyst reports can be overwhelming the first time you open them because of the sheer amount of numbers, making it hard to know where to start. Annual energy, specific yield, PR, irradiation, losses, array output, inverter output, energy exported to the grid, and other seemingly important values all appear together, so trying to follow everything from the start can actually make it harder to grasp the overall picture. The official PVSyst tutorial likewise presents the report in an order that is easier to understand: main results, the loss diagram, and monthly/daily graphs.

What's important in practical work is not memorizing every abbreviation. First look at the figures closest to the conclusion, then trace back the background conditions and the reasons for the losses. The official PVSyst help is divided into pages such as meteorology and solar irradiation, grid-connected system, PR, normalization indicators, and loss diagrams, each organizing which part of the results it explains. In other words, as long as you have an order to read them, PVSyst reports become very practical materials.

This article explains, in 10 items, the key points beginners should first grasp when reading a PVSyst report. Focusing on how to read the annual energy production, it systematically organizes topics from the solar irradiance conditions and losses underlying the results to monthly biases and points to note for self-consumption projects. It is compiled to be useful not only for those who are about to start using PVSyst, but also for those who check reports for internal reviews or to explain them to clients.

Table of Contents

• 1 Check the project conditions at the beginning of the report

• 2 Grasp the conclusions in Main results

• 3 Confirm the installed capacity and layout

• 4 Check GlobHor and weather conditions

• 5 Understand the difference between GlobInc and GlobEff

• 6 Read Produced Energy correctly

• 7 Understand Specific production and PR separately

• 8 Use the Loss Diagram to see where losses occurred

• 9 Distinguish between EArray, EOutInv, and E_Grid

• 10 Look for anomalies in the monthly results and Daily Input/Output

• Summary

1 Review the project conditions at the beginning of the report

The first thing to look at is the project conditions summarized at the beginning of the report. This section contains information that forms the basis for the results, such as site conditions, orientation and tilt, and the array’s capacity and configuration. The PVSyst tutorial also explains that it’s important to check the summary of simulation conditions before viewing the results, so you can spot any obvious input errors early. In other words, before checking the generation figures, confirming “what this report actually calculated” is the starting point for reading a PVSyst report.

What beginners often overlook is that they look only at the annual power generation without first confirming whether the capacity and orientation match their assumptions. For example, if a project you thought faced south is actually split across east- and west-facing surfaces, or if the configuration has a smaller capacity than assumed, no amount of reading the generation figures on later pages will prevent a misinterpretation. In other words, verifying the conditions at the start of the report is not a mere formality but the foundation for correctly interpreting the results.

Also, by noting the project conditions here, when you later look at the Loss Diagram or the monthly results it will be easier to connect whether "this loss is natural because it's on east- or west-facing surfaces" or "this winter's dip is due to the tilt conditions." PVSyst can be used adequately by looking only at the results, but reading them together with the conditions makes their meaning much clearer. In other words, having the project conditions in mind in the first few dozen seconds will greatly affect how quickly you understand things afterward.

2 Draw conclusions from Main results

The next thing to look at is the Main results. In PVSyst’s official tutorial, the Main results page is treated as the centerpiece of the simulation results, and it explains that energy production, specific yield, and PR are summarized and displayed there. In other words, this is the first conclusion page when reading PVSyst.

The first things to look at in Main results are three points: how much generation is expected annually, what it looks like per unit of installed capacity, and how the system performs as an integrated whole. By looking at these you can grasp the project's overall outline. Even without proceeding to root-cause analysis, you can organize it as: "This project is expected to generate this much per year, this is how it appears per unit of scale, and the system is finished to this degree." In other words, Main results is the starting point for verifying the answers.

A common mistake beginners make here is judging performance solely by the annual energy production figure. In PVSyst reports, alongside the total energy production there are values normalized by capacity and the PR, so if you only look at the total amount the difference in system size will appear directly as a difference in results. In other words, if you understand that Main results is not a place to look at a single number but a place to grasp multiple perspectives together, it becomes easier to read.

3 Check the installed capacity and surface configuration

The third thing to check is the installed capacity and the array configuration. When reading PVSyst results, it’s easy to focus only on the annual energy in kWh, but underlying that is the installed capacity in kWp and the configuration of how much is mounted on each surface. In the variable list for grid-connected systems, PnomArray is the basis of installed capacity and is treated as an important value that also appears in the denominator of EArrRef and PR. In other words, to understand energy generation you need to avoid misreading the capacity.

Surface configuration is also important. Whether it is a single south-facing surface, distributed across east–west surfaces, or has multiple orientations, the time-of-day characteristics of generation and the way losses occur will differ even for the same capacity. In PVSyst, the irradiance conditions through azimuth and tilt are reflected in GlobInc, so if you overlook the surface configuration you won't understand "why this amount of generation" occurs. In other words, capacity only becomes meaningful when you look not just at the number but at how it is distributed across the surfaces.

Also, this perspective is indispensable when looking at comparative cases. Even if you are comparing 10kWp and 10kWp, if one is mainly south-facing and the other includes east-west dispersion or north-oriented surfaces, a difference in the total of the Main results is natural. If you compare only the results without reading the installed capacity and surface configuration, PVSyst becomes usable only as "hit-or-miss" material. In other words, installed capacity and surface configuration are fundamental information for reading generation results in context.

4 Check GlobHor and meteorological conditions

The fourth thing to examine is the meteorological conditions centered on GlobHor. In PVSyst’s official help, GlobHor is defined as the global horizontal irradiance read from the meteorological data file. This is the basic value that indicates how much solar radiation is received from the sky at that location. In other words, the foundation of power generation lies first in the meteorological conditions of the site.

What you should be checking here is whether the results are being strongly affected by meteorological conditions before equipment-related factors. When annual power generation is lower than expected, it's tempting to immediately assume a problem with equipment performance or design, but it may be that the site's solar irradiation is inherently poor. Conversely, if meteorological conditions are good but generation doesn't rise, you should suspect subsequent losses or issues on the equipment side. In other words, GlobHor is a figure that tells you the starting point — how much solar irradiation you can expect at this location.

Also, because PVSyst’s weather-related results can be broken down by month or by hour, they provide an entry point for looking at seasonal differences as well as annual totals. Whether summer is strong, whether there is a large drop in winter, or whether production is relatively even throughout the year will significantly change how you interpret the later monthly generation figures. In other words, grasping the weather conditions makes it easier to read the other pages of the report as “generation under those conditions” rather than simply “generation for that year.”

5 Understand the differences between GlobInc and GlobEff

The fifth thing to look at is the difference between GlobInc and GlobEff. In PVSyst, GlobInc is defined as the global irradiance incident on the receiving surface, while GlobEff is defined as the effective irradiance after subtracting optical losses. In other words, it is helpful to think of GlobInc as "light that reached the surface" and GlobEff as "light that effectively reached the cell."

This difference is important because it makes losses that cannot be explained by orientation and tilt alone easier to discern. In the official help, values are shown in the order GlobHrz, GlobShd, GlobIAM, GlobSlg, GlobEff, corresponding to far-field shading, near-field shading, IAM, soiling, etc. In other words, even if GlobInc is sufficient, a drop in GlobEff indicates significant shading or optical losses.

Beginners often find themselves puzzled when there is plenty of solar irradiation but little power generation. However, PVSyst allows you to clearly separate these differences. Simply comparing GlobInc and GlobEff can significantly narrow down whether the problem is due to site conditions, roof conditions, or optical losses. In other words, it’s important to develop the habit of looking at what is happening at the point where light enters the system, rather than just looking at the generation results.

Also, this perspective is useful when explaining the effects of shading. In projects with nearby shading, GlobInc may not be that bad, but GlobEff can fall below expectations. Being able to explain such differences makes it much easier to communicate with clients and within the company. In other words, GlobInc and GlobEff are important intermediate indicators that link results and causes.

6 Understand Produced Energy, Specific Production, and PR Separately

The sixth thing to look at is to understand Produced Energy, Specific production, and PR separately. In PVSyst's official tutorial, these three are presented as the main results, and it makes clear that each plays a different role. Produced Energy is the total energy generated; Specific production is the energy produced per unit of installed capacity; PR is a way of evaluating system quality relative to solar irradiation conditions. In other words, they are not similar numbers but three indicators with distinct meanings.

Produced Energy is the clearest figure showing how much electricity was ultimately obtained from that project. However, because it is a total amount, projects with larger installed capacity tend to look more favorable. Looking at this alone, larger installations appear better. In other words, it is useful for comparing total quantities, but somewhat unsuitable for comparisons across different equipment scales.

Specific production is an indicator obtained by dividing Produced Energy by the installed capacity. In the PVSyst tutorial, this is also described as “Produced energy divided by the nominal power of the array.” In other words, it’s a figure that shows how much energy is generated per 1 kWp per year, making it easier to compare projects. Because differences in azimuth, shading, and losses become visible across different system sizes, it’s an indicator that is very easy for beginners to use.

PR also has another role. In the official help, PR is defined as E_Grid / (GlobInc × PnomPV) and is described as an indicator akin to overall efficiency that includes optical losses, array losses, and system losses. Unlike Specific production, PR is less directly dependent on meteorological conditions and plane orientation, making it easier to compare the "coherence" of systems across different sites and orientations. In other words, PR is neither a measure of total output nor of scale, but a figure for assessing equipment quality.

The important point here is not to confuse these three. A large Produced Energy does not necessarily imply a high PR, and a high PR does not necessarily mean a large total energy production. In other words, it is better to understand that PVSyst's Main results is not a single ranking table but a page that shows the three separately: "total", "per unit of size", and "quality". Simply knowing this will greatly reduce misinterpretation of the report.

7 Use the Loss Diagram to see how power output declines

The seventh thing to look at is the Loss Diagram. According to PVSyst’s official documentation, this diagram is meant to quickly grasp the quality of the system design and is used to identify the main sources of loss. Furthermore, it is always displayed in the annual report and can be checked on a monthly basis. In other words, the Loss Diagram is the central diagram for seeing why the energy production turned out the way it did.

In this figure, you can see in sequence where solar irradiance is reduced, where it is reduced in the array, and where it is reduced in the inverter and on the AC side. The tutorial also explains that the Loss Diagram shows the energy balance and all losses and is a powerful indicator for judging the quality of a design. In other words, if the Main results are the conclusion, the Loss Diagram is the page that shows the reasons for that conclusion at a glance.

What beginners should focus on here is not memorizing every detailed variable name, but grasping where the output drops significantly. It is enough to know whether optical losses are large, temperature losses are large, mismatch or wiring are having an effect, or whether losses are occurring in the inverter. In other words, the Loss Diagram is easier to read when used not for rote memorization of details but as a figure for identifying weak points.

The Loss Diagram is also very well suited for comparing design options. When comparing a south-facing option with an east–west option, or options with and without shading, you can see not only the difference in annual power generation but also at which stages the differences arise. This provides clues for design improvements. In other words, looking at a Loss Diagram not only helps you understand the results, but also leads you to consider where to make improvements next.

Summary

When organizing a PVSyst report for beginners, the first things to grasp are the project conditions at the start of the report, the Main results, the installed capacity and system/layout configuration, GlobHor, GlobInc and GlobEff, the differences between Produced Energy, Specific production and PR, and the Loss Diagram. Reading in this order makes it less likely to confuse the meaning of the numbers and makes it much easier to interpret the energy production. PVSyst reports contain many numbers, but if you follow them in sequence—from conclusions to background and then to the reasons for losses—the reports are by no means difficult.

The important thing is not to think of PVSyst as just a collection of acronyms, but to regard it as a document for reading the flow of energy. Look in order at how much solar radiation enters, how much effectively reaches the system, where and by how much it is lost, and ultimately how many kWh can be extracted. If you grasp this flow, even beginners will be able to capture the main points of the report quite well.

Also, if you truly want to improve the accuracy of interpreting these reports, the precision of the input conditions is essential. If roof edges, obstructions, elevation differences, or the way nearby shading occurs are ambiguous, the figures in the Loss Diagram and Main results can fluctuate. In particular, shading and effective-area conditions directly affect GlobEff and the way losses appear.

In that respect, as a means of accurately capturing on-site spatial relationships, the LRTK—an iPhone-mounted GNSS high-precision positioning device—is extremely effective. Because it makes it easier to accurately record the positions of roof edges and obstacles on site, it becomes easier to improve the accuracy of the input assumptions for PVSyst. If you want to read PVSyst reports in a form that is truly usable in practice, firmly capturing on-site conditions with measures like LRTK is a major advantage that improves even the precision of result interpretation.