What makes PVSyst difficult? Six stumbling points for beginners

PVSyst is photovoltaic simulation software used to examine a solar power system’s energy production, losses, and the validity of its design conditions. Because it can organize practical information—such as plant planning, design, financial analysis, specification comparisons, and report generation—into a single workflow, it is one of the important tools for people involved in solar power generation. However, for beginners, the large number of screen items, the technical nature of input parameters, and the difficulty of knowing what to check on the results screens can make it easy to become confused.

The reason PVSyst feels difficult is not simply that the interface is complicated. Because multiple factors—meteorological data, tilt angle, azimuth, module specifications, inverter conditions, shading, temperature, wiring, losses, energy production, performance ratio, and so on—are interrelated, it is hard to understand how a single setting change will affect the final result. Furthermore, in practice it is not enough to “just get a result”; you must be able to explain those numbers, judge whether the design conditions are reasonable, and translate them into a report that can be understood by stakeholders.

This article is aimed at practitioners searching for "What is PVSyst" and organizes six points where PVSyst beginners are likely to stumble, explaining the background of each and how to overcome them. Rather than just memorizing operational procedures, by understanding what each item means and where judgments are required, you can build a foundation for using PVSyst in practical work.

Table of Contents

• What is PVSyst software used for?

• Challenge 1: Difficult to understand the meaning of meteorological data

• Challenge 2: Hard to grasp the relationship between installation conditions and power generation

• Challenge 3: There are many loss items, making it difficult to prioritize them

• Challenge 4: Easy to get confused when configuring module and inverter settings

• Challenge 5: Easy to struggle with reading the result screens and reports

• Challenge 6: Requires the ability to justify the validity of input values

• How to learn to use PVSyst in practice

• Summary

What is PVSyst used for?

PVSyst is simulation software for predicting the energy output of photovoltaic systems and for checking differences between design conditions and the breakdown of losses. When evaluating solar power generation, simply looking at system capacity does not reveal the annual energy yield. Even systems with the same capacity can deliver very different amounts of energy depending on local irradiance, panel orientation, tilt angle, surrounding shading, temperature, equipment configuration, wiring length, soiling, conversion efficiency, and other factors. PVSyst is used to enter these conditions and to calculate annual or monthly energy production, losses, and performance indicators.

One thing beginners should understand from the outset is that PVSyst is not a tool that automatically produces the "correct answer", but a tool that evaluates power generation based on the assumptions entered. If the input conditions do not match the local situation, the output will also diverge from reality. Conversely, if you organize the rationale for the input conditions and appropriately reflect the site conditions, you can obtain results that are useful for design comparisons and feasibility assessments.

The difficulty of PVSyst lies less in the operation itself and more in understanding the relationship between inputs and outputs. On the screen you enter numbers for each item, but you must judge how well those numbers represent the actual site conditions, whether they are reasonable as general design values, and whether they are over- or underestimates. For example, even a small change in the installation angle can affect annual energy production, monthly generation trends, shading impacts, mounting structure design, and site utilization. It is important to understand these not as isolated items but as design conditions for the entire power plant.

Because PVSyst outputs results as numbers, graphs, and reports, beginners can easily be unsure about "which figures to look at." If you judge based only on annual energy production, you may overlook the causes of losses and weaknesses in the design. By checking together the monthly generation, the performance ratio, the progression from irradiance to effective generation, and the magnitudes of the various losses, the meaning of the results becomes clear.

When learning PVSyst, you don’t need to master every feature perfectly from the start. First, it’s important to follow how different assumptions lead to different results. If you grasp the overall flow—meteorological conditions, installation conditions, equipment conditions, loss conditions, and output results—the detailed setting items will become easier to understand little by little.

Challenge 1: Meteorological data are difficult to interpret

One of the first things beginners in PVSyst tend to stumble over is handling meteorological data. In solar power generation simulations, irradiance forms the foundation of energy production. However, even when we talk about irradiance, there are multiple concepts: irradiance on a horizontal plane, irradiance on an inclined plane, the direct component, the diffuse component, the reflected component, and so on. For beginners, it can be difficult to tell which data they are looking at and which values directly affect the energy output.

The power output of a solar PV system is largely determined by how much solar irradiance reaches the panel surface. The irradiance values provided as meteorological data are generally based on observation sites or estimation models and do not necessarily fully represent the actual local conditions. In mountainous areas, coastal areas, snow-prone regions, fog-prone regions, and urban areas, local meteorological conditions can differ even under the same place name. Therefore, when importing meteorological data into PVSyst, you should not simply select the nearest site; you need to verify whether it closely matches the meteorological characteristics of the target site.

One point that often confuses beginners is that meteorological data are not the sole determinant of power generation, but they do serve as a benchmark for power generation forecasts. In other words, if the meteorological data differ significantly, no matter how finely you adjust equipment parameters and loss settings, the final result will be hard to match to reality. Conversely, even if the meteorological data are reasonable, if settings such as installation angle, shading, or temperature conditions are inappropriate, the power generation forecast will be off.

It is also important to examine monthly variations in solar irradiance. Even if the annual total looks reasonable, the monthly trends may not align with the site’s climate. For example, when considering impacts on energy production from the rainy season, snow cover, winter irradiance conditions, or high summer temperatures, the annual value alone is insufficient. In practical work using PVSyst, you should check not only the annual energy yield but also the monthly energy yields and monthly loss trends, and verify that they are not inconsistent with regional characteristics.

To overcome the challenges of meteorological data, it is important first to understand that "solar irradiance is the gateway to power generation." The calculation of power generation is the flow in which the energy arriving from the sun is received on the panel surface, converted into direct current power, and then further transformed into alternating current power in a usable form. If the assumption about irradiance, which is this gateway, becomes unstable, all subsequent calculations are affected. Beginners should make a habit of treating meteorological data not as mere input items but as the foundation of the entire simulation.

In practice, there are situations where you need to explain the source of meteorological data and the reasons for choosing it. In such cases, simply saying “we used data from a nearby site” may be insufficient. Taking into account the target site's latitude, elevation, surrounding environment, climate trends, and past observation patterns, and organizing why those meteorological conditions were adopted will increase the credibility of the simulation results. Before becoming familiar with operating PVSyst, understanding the meaning of meteorological data is an important first step for beginners.

Challenge 2: Hard to grasp the relationship between installation conditions and power generation

A common stumbling block in PVSyst is the relationship between installation conditions and energy production. The azimuth, tilt angle, mounting height, row spacing, terrain, and surrounding obstacles of the solar panels directly affect the energy yield. However, for beginners it is difficult to intuitively grasp how much each condition influences the results. On the screen you simply enter numerical values, but those numbers are tied to the local design philosophy and construction conditions.

The orientation of the panels affects which times of day’s solar irradiance are prioritized throughout the year. The tilt angle influences seasonal generation patterns, how easily dirt is washed off by rain, and the impact of snowfall. Row spacing determines the balance between land-use efficiency and the impact of shading. If panels are packed too closely in an attempt to make efficient use of the site, installed capacity may increase while losses from inter-row shading can also rise. Conversely, widening row spacing makes it easier to mitigate shading effects, but the capacity that can be installed on the same site may decrease.

Beginners tend to assume when looking at PVSyst results that the larger the system capacity, the more generation will simply increase. Of course, increasing capacity generally makes generation more likely to rise, but you also need to check generation efficiency and any increases in losses. In particular, when placing many panels on a limited site, shading, wiring, and equipment configuration can prevent energy production from increasing as much as capacity does. Because PVSyst lets you quantify these design trade-offs, you should aim for a balanced design instead of a simple maximum-capacity approach.

Furthermore, installation conditions are also influenced by the accuracy of on-site surveys and drawing information. If information such as site boundaries, ground elevation differences, locations of obstacles, existing structures, and surrounding trees remains unclear, the layout in the simulation may be tidy yet differ from actual field conditions. The orientation, tilt, and shading settings in PVSyst cannot be separated from the organization of on-site information. Adjusting only input values while site conditions remain unclear is unlikely to produce results that are reliable in practice.

The difficulty of defining installation conditions also lies in the fact that there is no single correct answer. Appropriate design conditions change depending on whether you want to maximize annual energy production, prioritize winter energy production, suppress peak output, prioritize site efficiency, or emphasize constructability.

PVSyst is easier to understand when used as a tool to compare those differences. Beginners should not judge based on a single simulation result; by comparing multiple cases with different orientations, tilt angles, and layout conditions and checking which factors are affecting energy production, their understanding will deepen.

When using PVSyst in practice, installation conditions also affect consensus-building among stakeholders. Designers, construction personnel, project owners, and maintenance staff each view things from different perspectives. You need to consider not only energy yield but also ease of construction, ease of inspection, future management, and adaptability to terrain. PVSyst settings are not merely numbers in a simulation; they directly influence decisions about how to actually build the power plant. Keeping this awareness makes the input of installation conditions more practically meaningful.

Difficulty 3: There are many loss items, making it difficult to set priorities

One of PVSyst's features is that it lets you examine in detail the losses leading up to the energy output. However, that very level of detail becomes a major hurdle for beginners. To understand how the final energy production is ultimately reduced—irradiance losses, shading losses, temperature-related losses, mismatch, wiring losses, conversion losses, soiling, degradation, downtime, and curtailment—you need to interpret multiple items in sequence.

Beginners often become unsure which loss items they should prioritize when they look at them. Ideally, all losses would be minimized, but in practice there is a balance with cost, constructability, site conditions, equipment selection, and maintenance planning. For example, widening row spacing to reduce shading losses can reduce installed capacity. It may also be necessary to optimize equipment layout to reduce wiring losses. Temperature losses are influenced by regional conditions and installation methods, so they cannot be resolved simply by changing set values.

What’s important when understanding PVSyst is not to lump losses together as simply “bad.” In solar power generation, a certain amount of loss will inevitably occur. The key is to distinguish whether those losses are within a natural range or indicate a design issue. For example, it is natural for temperature-related losses to be larger in regions with high temperatures, but if shadows from surrounding obstacles are larger than anticipated, the layout and shading conditions should be reviewed. If wiring losses are large, the equipment placement, cable routing, and alignment with the electrical design need to be checked.

When reading the loss items, it is effective to view the flow to see at which stage the generated power is decreasing. First there is solar radiation energy, which is received at the panel surface, becomes DC power, is then converted to AC power, and finally becomes the usable generated power. Checking where in this flow the largest reductions occur makes it easier to identify the source of the problem. Rather than looking only at individual loss rates, it is important to check how much impact they have on the total generated power.

Also, losses are related to both the input values and the output results. Beginners tend to look only at the losses shown on the results screen, but those stem from the input conditions. Shading losses are tied to the shading-condition settings, temperature losses to the weather conditions and installation method, wiring losses to the electrical design, and soiling losses to the local environment and maintenance plan. In other words, you should not stop at looking at the losses; you need to go back to the input conditions and check why those losses occurred.

To determine the priority of loss items, the basic approach is to first check the largest losses. However, a large numerical value does not necessarily mean it is a problem. You need to distinguish whether the loss is hard to avoid due to natural conditions, can be improved through design, or can be managed through operation. Once you can make this distinction, PVSyst’s results become not just a calculation table but material for decision-making on design improvements.

Difficulty 4: It's easy to get confused when configuring module and inverter settings

In PVSyst, configuring the conditions for solar modules and inverters is also important. What is difficult for beginners is that they must not only enter the equipment specification values but also understand how the combination of those values affects energy production and losses. Because many electrical conditions are involved—module output, temperature characteristics, voltage, current, string configuration, inverter capacity, input range, conversion efficiency, and the concept of oversizing—personnel with limited design experience often stumble here.

In photovoltaic power systems, the direct current (DC) power generated by the modules is converted to alternating current (AC) power by the inverter. If the output characteristics of the modules are not matched to the input conditions of the inverter, efficient power generation cannot be achieved. If the number of modules connected in series per string or the number of parallel strings is not appropriate, the available voltage range may become limited, and under certain conditions output limiting may occur. PVSyst lets you check the effects of such combinations, but beginners may take time to understand the meaning of warnings and loss displays.

One area that often causes confusion is the relationship between installed capacity and inverter capacity. In solar power generation, module capacity and inverter capacity do not necessarily have to be the same. Combinations of capacities are considered based on solar irradiance and temperature conditions, the frequency of generation peaks, economic considerations, and design strategy. However, choosing the wrong combination can result in increased output clipping during peak periods and reduced efficiency under low-irradiance conditions. Checking output clipping and conversion losses in PVSyst results makes it easier to judge whether the equipment configuration is appropriate.

Module temperature characteristics are another factor that beginners often overlook. Solar modules tend to generate more power when solar irradiance is strong, but their output generally decreases as temperature rises. In other words, on clear, hot days irradiance may be high, yet temperature-related output losses also occur. If you do not understand this relationship, you cannot explain why energy production does not increase as much as expected despite high summer irradiance. In PVSyst, because temperature conditions affect energy yield, it is important not to look at irradiance alone but to check temperature losses as well.

Also, equipment conditions are related to actual procurement and design changes. If the equipment assumed at the planning stage differs from the equipment actually adopted, the simulation results may also change. If module or inverter specifications change, output, voltage range, conversion efficiency, temperature characteristics, and the way losses occur will also change. In practice, you should treat the rough simulations performed in the early planning stage separately from the simulations in the detailed design stage, and update input values as equipment conditions are finalized.

For beginners to get past this sticking point, it’s important not to view equipment specifications as mere tables of numbers, but to understand them along the flow of power generation. Sunlight is received and DC power is produced; that DC power enters the inverter and is output as AC power. If you map out where voltage, current, capacity, and efficiency come into play within this flow, the PVSyst settings screens become much easier to read. You may be overwhelmed at first by detailed technical terms, but by learning to connect the flow of generation with the roles of the equipment, the meaning of the settings will gradually become clearer.

Challenge 5: Users often struggle with interpreting the results screen and reports

When you run a simulation in PVSyst, various results are displayed, such as energy production, losses, performance indicators, monthly data, and reports. For beginners, a major challenge is knowing what to look at here. If you only check the annual energy production and stop there, you will not be able to fully understand the quality of the design conditions or the causes of losses. What is needed in practice is the ability to read the results, explain them, and, when necessary, review the input conditions.

First, you should check whether the annual energy generation deviates significantly from the assumptions in the plan. However, annual generation is the final result and does not tell you the reasons. Whether generation is higher or lower than expected, you need to check solar irradiation conditions, installation conditions, shading, temperature, equipment configuration, and the breakdown of losses. If the results differ from expectations, it is important not to simply adjust the numbers but to verify which assumptions are affecting the outcome.

Monthly generation is also an important item to check. Even if the annual total looks reasonable, the monthly variations may not match local conditions. For example, in regions where snow accumulation or low insolation has a large impact in winter, if the winter generation appears unnaturally high, you should review the meteorological conditions and loss settings. If generation struggles to increase in summer, losses due to high temperatures or output limitations may be the cause. Reading monthly trends makes it easier to spot issues that are not visible from annual values alone.

The performance ratio is another metric that beginners may take time to understand. The performance ratio is used as an indicator to assess how effectively a system is generating electricity relative to the solar irradiance conditions. However, the performance ratio should not be used alone to judge good or bad; it needs to be considered together with regional conditions, design parameters, and the nature of losses. A high performance ratio does not necessarily mean an excellent design, nor does a low performance ratio necessarily mean a poor design. It is important to be able to explain why a given value has been obtained, taking into account conditions such as shading, temperature, output limitations, and soiling.

Even when it comes to reading reports, beginners can easily stumble. A PVSyst report organizes many input conditions and results, but when explaining to stakeholders in practice, you don’t need to treat every item with the same weight. What matters is extracting the information necessary for the purpose of the analysis. Which items you should look at depends on whether you want to check the power generation, explain the breakdown of losses, demonstrate the validity of the design conditions, or compare multiple options.

To learn how to read the results screen, you need to develop a habit of going back and forth between the input conditions and the results. Rather than judging based only on the results, return to the input conditions to check why those results were obtained. If shadow losses are large, check the shadow settings; if temperature losses are large, check the meteorological conditions and the mounting configuration; if conversion losses are a concern, check the inverter conditions. By repeating this back-and-forth, PVSyst reports become not merely output documents but can be used as a record of design studies.

Challenge 6: The ability to explain the validity of input values is required

When using PVSyst in practice, the most important—and yet where beginners often stumble—is the ability to justify the validity of input values. PVSyst allows many conditions to be entered, but which values to adopt is in part left to the user's judgment. Meteorological data, shading conditions, soiling, wiring losses, downtime rate, degradation, temperature conditions, and so on need to be considered according to local conditions and design policy. If the input values lack justification, the output results will not be convincing.

Beginners tend to focus first on completing the simulation, and organizing the rationale for input values often gets postponed. However, in practice there are occasions when you will be asked, "Why did you choose those values?" For example, you need to explain how much soiling loss you expect, how you set the effects of shading, whether the temperature conditions match the site, and whether the wiring losses are consistent with the electrical design. If you cannot present the rationale here, confidence in the simulation results themselves will be weakened.

When assessing the validity of input values, combine local site conditions, design drawings, equipment specifications, maintenance plans, general design standards, and past similar projects to make your judgment. You may not be able to fully grasp every condition, so it is important to document what assumptions you used to fill in any unknowns. When reviewing PVSyst results later, if the rationale for the input values has been retained, it will be easier to trace why the simulation produced those results.

Also, input values can be set conservatively or optimistically. If you try to make estimated power generation look high by understating losses too much, the gap between expected and actual performance during operation can become large. Conversely, overly conservative assumptions can lead to an unnecessarily low estimate of project viability. The important thing is to adopt assumptions appropriate to the objective. In the preliminary stage, it is useful to consider a range of possibilities, and in the detailed design stage, to improve accuracy based on site information and equipment specifications.

Ensuring the validity of input values is important even when comparing multiple cases. For example, when comparing a case with a changed installation angle, a case with a changed equipment configuration, and a case with changed shading conditions, if common conditions and changed conditions are not clearly distinguished, it becomes unclear what caused the differences in the results. In comparative evaluations, it is important to organize the items that were changed and to keep all other conditions as consistent as possible. By adhering to this basic principle, the reliability of design comparisons using PVSyst is improved.

Ultimately, what matters in PVSyst is not producing results but being able to explain them. Ideally, you should be able not only to state how much energy will be generated but also to explain which assumptions led to that estimate, which losses are significant, where there is room for improvement, and whether the results are consistent with on-site conditions. Beginners can develop practical, job-ready skills by, at the same time as learning how to operate the software, cultivating the habit of recording the rationale for their input values.

How to Learn PVSyst to Use It in Professional Practice

To become proficient with PVSyst in practical work, it is more effective to repeatedly review the basic workflow than to try to understand all the advanced features from the start. First, understand the sequence of selecting the meteorological data, entering the site conditions, setting the equipment parameters, checking the losses, and reading the results. By going through this sequence many times, you will naturally see how each item connects to the others.

In the early stages of learning, it is effective to change one parameter at a time and observe how the results change. By narrowing the items you alter—changing only the tilt angle, only the azimuth, only the shading conditions, or only the soiling loss—you can more easily understand how each change affects the outcome. If you change multiple conditions at once, it becomes difficult to tell which factor caused the difference in energy production. Because PVSyst is software used for comparative analysis, it is especially important to carefully track the implications of each condition change.

Also, when reviewing simulation results, it is good practice to check not only the annual power generation but also the monthly generation, the breakdown of losses, and performance indicators together. Even if the annual power generation is large, if there is an unusual trend in a particular month, there may be a problem with the input conditions. If the breakdown of losses is skewed, there may be room for design improvements. If performance indicators differ from expectations, you should recheck the irradiance conditions and loss conditions. Reading the results from multiple perspectives rather than relying on a single figure contributes to practical skills.

Furthermore, it is important to record the input conditions. Keeping a record of which meteorological data were used, which drawings the installation angle and orientation were based on, which on-site information the shading conditions reflected, and which assumptions underlie the loss settings will make later review and explanation easier. In practice, simulations are not run just once and finished; they are often updated repeatedly in response to design changes or revisions to the conditions. If the assumptions are vague each time, comparing results becomes difficult.

When learning PVSyst, it is more important to think about why a result occurred than to immediately judge whether the result is good or bad. If energy production is lower than expected, check one by one whether solar irradiance conditions are low, shading is significant, temperature losses are large, or the equipment configuration is having an impact. Likewise, if production is higher than expected, verify that no overly optimistic assumptions have been included. By repeating this verification, operating PVSyst becomes not just a data-entry task but a process for making design decisions.

For practitioners, the ability to explain PVSyst results to stakeholders is indispensable. Instead of simply listing technical terms, you need to clearly communicate what assumptions the generation estimates are based on and how much each loss affects them. Clients and internal stakeholders want to know not the detailed on-screen settings but how those results relate to design and business decisions. When learning PVSyst, being conscious not only of the ability to read reports but also of the ability to explain them will make it easier to apply the knowledge in practice.

Summary

PVSyst is simulation software for evaluating the energy production, losses, and design conditions of solar power systems. What is difficult for beginners is not just operating the interface. The hard part is that it involves many practical judgments required in real work, such as understanding the meaning of meteorological data, the relationship between installation conditions and energy production, how to read loss items, module and inverter settings, interpreting result screens and reports, and explaining the validity of input values.

What is particularly important is to use PVSyst not as "software to produce results" but as "a tool to organize the assumptions and to check their impact on power generation." If the input values do not match the actual site conditions, the output results will be hard to trust. Conversely, if you can organize the meteorological conditions, installation conditions, equipment conditions, and loss conditions together with their supporting rationale, the simulation results will become useful documentation for design review and for explaining the project to stakeholders.

Beginners should start by understanding the basic workflow and then check how changing each condition one by one affects the results. Rather than looking only at annual energy production, review monthly production, the breakdown of losses, and performance indicators together; by going back and forth between input conditions and results as you learn, your view of PVSyst will change significantly. If you know the points where people commonly stumble in advance, you won’t be overwhelmed by the number of items on the screen and can more easily focus on the checks required in practical work.

Also, improving the accuracy of PVSyst requires not only software settings but also a thorough understanding of on-site conditions. If information such as the site’s location, orientation, elevation differences, obstacles, and surrounding environment remains unclear, there are limits to assessing shading and layout conditions. In the design and simulation of solar power generation, it is important to connect desk-based settings with actual on-site measurement data.

If you want to streamline on-site surveys and position data acquisition and improve the accuracy of the assumptions reflected in PVSyst, using LRTK, an iPhone-mounted high-precision GNSS positioning device, can also be effective. Being able to obtain high-precision position data on-site makes it easier to organize site conditions and measurement point information, which leads to better on-site understanding and higher-quality design review before simulation. To use PVSyst effectively in practice, in addition to understanding the software, it is also important to establish systems for accurately handling field data.