PVSyst: 6 Initial Setup Checks to Avoid Mistakes in the Manual

Table of Contents

• Why initial settings in PVSyst are important

• Check 1: Correctly align project conditions and site information

• Check 2: Confirm how to select meteorological data and the data loading conditions

• Check 3: Prevent input errors for azimuth and inclination angles

• Check 4: Ensure the basic conditions for modules and inverters are in place

• Check 5: Do not leave the loss settings at their default values

• Check 6: Review the assumptions before generating the report

• Common mistakes and countermeasures in initial setup

• Tips for Using the PVSyst Manual in Practical Work

• Summary

Why the initial setup of PVSyst is important

When simulating the power output of a photovoltaic system using PVSyst, the initial settings are the most easily overlooked yet have the greatest impact on the results. Even if you think you are operating while referring to the PVSyst manual, small discrepancies in the site information, meteorological data, azimuth, tilt angle, equipment conditions, or loss assumptions can significantly change the final annual energy production, the performance ratio, and the appearance of monthly generation.

The difficulty of the initial setup lies less in the complexity of the input screen itself than in the fact that each field is linked to on-site conditions and design assumptions. For example, even if you use the same solar panels, the energy production will vary if the meteorological data for the installation site differs. If the tilt angle or azimuth of the mounting structure is different, the way it receives solar irradiation changes, and if shading is handled inadequately, generation estimates can be more optimistic than reality. While PVSyst allows very detailed condition settings, that high degree of freedom can lead to input errors or oversights.

Additionally, PVSyst simulation results are used in a variety of situations—internal reviews, explanations to the project owner, briefings for financial institutions, discussions with EPC companies, and comparisons of design proposals. Therefore, simply being able to operate the software is not sufficient. You need to be able to explain which assumptions the calculations were based on, why those settings were chosen, and under what conditions the figures in the report apply. Carefully checking the initial settings is an important preparation to prevent later rework and insufficient explanations.

By reading the PVSyst manual, you can verify the input fields on each screen and the way the calculations are performed. However, in practice it is important not just to follow the manual verbatim but to decide which items to prioritize based on your specific project. Especially for those using PVSyst for the first time or for people inheriting and editing a predecessor’s data, it is reassuring to set checkpoints for the initial settings before running the simulation.

This article organizes six initial settings to check to avoid failures for those working with the PVSyst manual as a reference. Rather than merely providing operational steps, it explains why each setting is important, what kinds of mistakes are likely to occur, and how to review them in practical work.

Check 1: Ensure project conditions and site information are correctly aligned

In PVSyst's initial setup, the first items to check are the project conditions and the site information. Solar power simulations are performed based on the installation site's latitude, longitude, elevation, time zone, site name, and meteorological conditions. If there are errors here, no matter how accurately you later enter the module or inverter specifications, the reliability of the results will be reduced.

What you should pay particular attention to is not to judge solely by the project name or the site name. In PVSyst you may be able to select similar place names or nearby locations, but the simulation site does not necessarily match the actual planned installation site. If you select a location only because the prefecture or municipality name is similar, differences such as coastal, mountainous, or inland conditions may not be reflected. In solar power generation, not only the annual solar irradiation but also temperature and seasonal weather patterns have an impact, so location information must be handled carefully.

When setting a site while consulting the PVSyst manual, first reconcile the project's basic information with the actual installation conditions. Verify that the latitude and longitude match maps and design documents, that the elevation is not drastically different, and that the time zone is correct. Pay particular attention for overseas projects or projects spanning multiple regions, as time zone discrepancies can affect monthly and hourly analyses.

Also, the project conditions should include clarifying the purpose of the simulation. The level of accuracy required for the initial settings varies depending on whether it is a preliminary estimate, the basic design phase, or an analysis close to detailed design. In the preliminary phase, it may be possible to proceed using meteorological data from representative locations, but if the results are to be used for business feasibility evaluations or as pre-contract documentation, more careful data selection and definition of conditions are necessary.

If you proceed with the initial settings while leaving project conditions vague, later you will need to confirm questions such as "Which location does this figure assume?" and "Does it match the conditions of the planned installation site?" In that case, you may have to not only rerun simulations but also revise comparison materials and explanatory documents. Firming up site information at the outset is important for improving the overall work efficiency of PVSyst.

Check 2: Verify the selection of meteorological data and the conditions for loading it

In PVSyst power generation simulations, the selection of meteorological data directly determines the results. Conditions such as solar irradiance, ambient temperature, and wind speed greatly affect a photovoltaic system’s annual energy yield and loss assessment. Even if you can follow the PVSyst manual to load meteorological data, choosing the wrong dataset can cause the simulation results to diverge from reality.

The first thing to check with meteorological data is the type of data. Depending on the project, you may use representative-year data, satellite-based data, observations from nearby monitoring stations, or external data imported by the user. Each data type has advantages and limitations; none is universally perfect. For example, satellite-derived data are easy to handle over wide areas but can struggle to adequately reflect local terrain effects, snow cover, sea breezes, or fog. Observation-station data provide the reassurance of actual measurements, but if the station is some distance away, differences from the local site can occur.

The next thing to verify is whether the imported meteorological data align with the simulation site. Check that the latitude and longitude are nearby, that the elevation difference is not too large, and that there are no anomalies in the monthly solar radiation trends. In particular, in mountainous or coastal areas, weather conditions can change noticeably over short distances. Just because you could select the data in PVSyst does not mean it is the best choice for the project.

Care must be taken with the units and formats of meteorological data. When importing external data, verify that items such as global horizontal irradiance, direct normal irradiance, diffuse irradiance, and temperature are correctly mapped. If the meanings of columns or the units are mistaken, simulation results can deviate significantly. While referring to the relevant sections of the PVSyst manual, it is important to carefully check the data formats, time intervals, and how missing values are handled.

In the initial setup, it is helpful for later stages to note why a particular set of meteorological data was adopted. When explaining the results afterward, being able to explain "why this meteorological data was used" increases the credibility of the simulation. This is especially important when comparing multiple design options: if the meteorological data are not standardized, you may end up comparing differences in weather conditions rather than differences in equipment conditions.

PVSyst lets you handle a lot of meteorological data through its interface, but what matters in practice is not whether the data could be loaded, but whether it is reasonable as an assumption for the project. Carefully checking the meteorological data during the initial setup makes it easier to avoid later numerical corrections and having to redo explanations.

Check 3: Prevent input errors for azimuth and tilt angles

The power output of a photovoltaic system varies greatly depending on which direction the solar panels face and at what angle they are installed. Therefore, confirming the azimuth and tilt angles is essential in PVSyst’s initial settings. Even when entering data while referring to the PVSyst manual, if you misunderstand the azimuth reference or sign convention, you can end up simulating conditions that differ from the intended installation orientation.

A common mistake with azimuth is confusing the notation on design drawings with the input rules in PVSyst. In typical design documents, directions such as true south, true north, and east–west are often described in words, and the angular reference can vary between documents. In PVSyst, however, you must enter the azimuth according to the software’s definitions. If you mix up how you treat south-facing versus east–west-facing orientations, or eastward tilt versus westward tilt, the energy yield and the monthly output trends will change.

Also confirm that the design tilt angle and the entered value match. For ground-mounted installations, this is the rack tilt angle; for roof-mounted installations, it is the roof pitch; for agrivoltaic or special racking, the structural angle is relevant. When converting roof pitch from materials shown as a dimensional ratio into an angle, conversion errors are likely to occur. If slope notation, degree notation, and percent notation are mixed, be sure to unify them before entering them into PVSyst.

Furthermore, for installations with multiple faces, check whether it is acceptable to treat all of them as having the same azimuth and tilt angle. Factory roofs and commercial facility roofs may be divided into multiple installation faces, such as south, east, and west. Even for ground-mounted installations, site conditions can cause some arrays to have different orientations or tilt angles. Treating these as a single face can result in deviations from the actual power generation characteristics.

Azimuth and tilt angles are items that can be entered relatively easily when operating PVSyst. However, precisely because they can be entered easily, there is a risk of proceeding without verifying them. After configuring them, check again whether the direction and angle are as intended by looking at the array conditions on the screen and the descriptions in the report. Especially when working with multiple people, sharing the correspondence between the notation on the design drawings and the PVSyst input values can prevent misunderstandings during review.

If the azimuth and tilt angles are correctly aligned during the initial setup stage, subsequent shading analysis, loss assessment, and energy yield comparisons will be stable. Conversely, if there is an error at this stage, all later evaluations will be built on incorrect assumptions. While referring to the PVSyst manual, it is essential to always cross-check the input rules against the notations in the project documentation.

Check 4: Establish basic requirements for modules and inverters

In PVSyst's initial setup, the basic parameters of the solar module and inverter are also important. Energy yield simulations are conducted not only based on meteorological and installation conditions but also on the electrical characteristics of the equipment used. Proceeding with provisional selections for modules or inverters, or choosing different products with similar model numbers, can introduce inaccuracies into the results.

What you should check in the module settings are output, temperature coefficient, voltage and current characteristics, the number of modules, and the string configuration. Even if you select a product listed in PVSyst’s database, verify that it matches the actual model number you plan to use. Even within the same manufacturer’s series, there can be differences in output or specification changes. If you accidentally choose a similar model number, the capacity and temperature characteristics may differ from the intended conditions.

In the inverter settings, check the rated capacity, number of MPPTs, input voltage range, maximum input current, conversion efficiency, and so on. If the module string configuration does not match the inverter’s input conditions, it will affect voltage range warnings, clipping losses, and mismatch assessments. Even when working while referring to the PVSyst manual, it is important not merely to select equipment but to verify that the modules and inverter form a valid combination.

Also, the ratio of DC capacity to AC capacity is a point you should check in the initial settings. In designs that assume oversizing, some output curtailment or clipping may occur. That itself is a design choice, but if the system is unintentionally oversized or, conversely, if the inverter capacity is too large, the evaluation of the design proposal will change. When comparing system capacities, verify the DC-side capacity, AC-side capacity, number of modules, and number of inverters together.

In string design, the open-circuit voltage at the lowest temperatures and the operating voltage at high temperatures must also be taken into account. In PVSyst, warnings and check functions may be displayed, but you should not assume that there is no problem simply because no warning appears; it is necessary to verify against the design conditions. Especially for cold regions, high-temperature areas, and large-scale projects, it is important not to underestimate voltage variations due to temperature conditions.

Equipment settings can be changed later, but altering them partway through can change the meaning of comparison results. For example, if the first proposal uses a temporary module and the next proposal uses a module that more closely resembles the actual unit, it becomes difficult to tell whether differences in power generation are due to layout differences or to differences in equipment characteristics. It is important to organize equipment conditions at the initial setup stage and to clearly indicate when settings are provisional.

Check 5: Do not leave the loss settings at their default values

When evaluating energy yield with PVSyst, loss settings are extremely important. In photovoltaic installations, energy output is reduced by various factors such as module temperature, wiring, mismatch, soiling, shading, angle of incidence, inverter conversion losses, shutdowns, and degradation. The PVSyst manual describes the rationale for each loss item, but in practice you must always verify whether it is acceptable to use the default initial values as-is.

A common mistake in loss settings is becoming complacent because initial values are pre-filled. PVSyst may provide default settings based on typical values and standard assumptions, but those are not necessarily suitable for every project. For example, in areas with a lot of sand and dust, regions with snowfall, coastal areas where salt damage is a concern, or roof installations with a low slope where dirt does not wash off easily, the approach to soiling loss should be reviewed on a per-project basis.

Wiring losses are also important. Losses vary depending on the cable lengths on the DC and AC sides, the cable size, and the voltage conditions. In the rough estimate stage, standard values may be used, but as the design approaches the detailed stage, it is necessary to review them according to the actual wiring plan. If wiring losses are underestimated, there is a risk of overestimating power generation.

Temperature losses are influenced by the module mounting configuration and ventilation conditions. The way module temperature rises can differ between ground-mounted, well-ventilated installations and those installed close to a roof. Because module output decreases as temperature increases, special attention is required for high-temperature regions and roof-mounted projects. Verify that the thermal model and installation conditions in PVSyst match the actual project conditions.

Shadow losses are an item for which you should establish a policy during the initial setup stage. Whether you create a detailed 3D scene, treat nearby obstructions in a simplified way, or how much of the terrain and surrounding buildings’ shadows you include will affect the simulation accuracy and workload. It is not necessary to input everything in detail, but if you proceed with simplified settings on projects where shadows have a large impact, the predicted power generation may be higher than the actual output.

Loss settings are an important explanatory element in PVSyst result reports. By examining not only the final energy production but also how much each loss contributes, you can identify directions for design improvements. Organizing the loss conditions in the initial setup makes it easier to explain the meaning of the figures when you read the report later.

Check 6: Review assumptions before generating the report

When you run a simulation in PVSyst, you can generate a report that includes energy production, performance ratio, loss diagrams, and monthly data. However, before creating the report, it is important to review the assumptions in the initial settings once again. Because reports are often used as explanatory materials, producing them with incorrect assumptions can give stakeholders the wrong impression.

What you should check first is the project information displayed in the report. Verify that the project name, location, system capacity, modules, inverters, azimuth, tilt angle, and meteorological data are as expected. Even items entered while referring to the PVSyst manual can retain old conditions after repeated duplication or editing. In particular, when creating a new project by copying data from a past project, the project name, location information, and some loss settings may remain from the previous project.

Next, check the overall picture of the simulation results. Verify whether the annual energy production is not unreasonably high or low relative to the system capacity, and whether the monthly generation trends do not strongly contradict the region’s solar irradiation conditions. Because PVSyst calculates based on the input conditions, it can produce reports that look plausible even when there are errors in the inputs. That is why a visual, human check of the results’ validity is indispensable.

Checking the loss diagram is also important. The loss diagram allows you to trace the flow from solar irradiance to the final AC output, so it can help you find mistakes in the initial settings. For example, you might notice that temperature losses are larger than expected, wiring losses are extremely small, shading losses are hardly reflected, or inverter losses and clipping differ from what was assumed. It’s important to look not only at the numbers but also at the balance of losses.

Also, when submitting a report externally, check that explanations of the assumptions are not lacking. If the source of meteorological data, the design stage, whether provisional settings were used, the scope of shading analysis, the approach to loss conditions, and similar items remain ambiguous, you will receive more questions later. PVSyst reports are convenient, but they do not necessarily provide a complete practical explanation on their own. Preparing supplementary materials or a memo of assumptions as needed makes it easier to align understanding with stakeholders.

The review before generating a report is not merely a final check. It is a review process to verify consistency from the initial settings through to the simulation results. By taking this extra step, you can more easily prevent submitting incorrect materials or having to redo calculations.

Common Mistakes and Countermeasures in Initial Setup

One common mistake in PVSyst initial setup is forgetting to update some conditions when reusing data from past projects. In PVSyst it is common to duplicate an existing project to create a new one, but if the site, meteorological data, loss settings, equipment configuration, report name, and so on remain from the previous project, you may end up running simulations under incorrect conditions. Reusing data is an efficient method, but after duplicating you must verify each project-specific condition individually.

Another common issue is the mixing of provisional settings with finalized settings. In early-stage studies, because equipment and layouts have not been decided, temporary modules, temporary inverters, and estimated loss values may be used. That in itself is not a problem. However, if you proceed without recording that these settings are provisional, those figures can later be treated as finalized values. It is important to note which conditions are provisional in PVSyst notes and filenames and in internal management documents.

Selecting the wrong weather data is also a common mistake. There are cases where a location that appeared nearby was chosen, but in reality its elevation and terrain were very different. Especially in mountainous areas, snowy regions, and coastal zones, nearby data cannot necessarily be used as-is. Comparing multiple datasets and checking for any inconsistencies in monthly solar radiation and temperature trends can reduce errors in the initial stages.

Be careful about sign errors in the azimuth. If you enter the east–west orientation or the deviation angle from south reversed, not only the annual energy yield but also the generation profile by time of day will change. In self-consumption projects, because the balance of generation between morning and afternoon affects alignment with demand, mixing up the azimuth can also impact economic analysis. After entering data, always verify it against the drawings and layout plans.

Loss settings are often overlooked. In particular, soiling loss, wiring loss, shading loss, and temperature conditions are items that tend to differ between projects. Even when using the default values, make sure you can explain why those values are acceptable. Values you cannot explain are likely to be flagged during later reviews.

Finally, there is a failure that comes from feeling reassured by looking only at the report. Although PVSyst's reports are well organized and easy to read, they do not automatically detect errors in the input conditions. Because the results are presented in a neat format, the content can appear to be correct. When reviewing a report, it is important to check the consistency between the assumptions and the results, rather than judging by appearance.

Practical Tips for Using the PVSyst Manual

To use the PVSyst manual in practice, it is important to consult it according to your workflow rather than simply reading it from start to finish. In the initial setup there is a practical order of checks—site information, meteorological data, system configuration, loss settings, and report verification. Even while reading the manual's screen explanations, using it with an awareness of what you need to check for your own project will deepen your understanding.

For beginners, it is recommended to start with a single standard project and experience the full workflow from the beginning through to report output. Trying to fully understand every item can easily lead to confusion along the way. At first, grasp the overall flow, and then dive deeper into individual items such as meteorological data, equipment settings, loss settings, and shading analysis so that the operations and the underlying theory become easier to connect.

On the other hand, to enable practitioners to work efficiently, creating an internal checklist is effective. The PVSyst manual provides detailed explanations, but it's inefficient to search for the verification points for each project from scratch every time. Organizing checklist items according to the types of projects your company frequently handles—such as ground-mounted, rooftop, self-consumption, battery-integrated, and agrivoltaic systems—stabilizes the quality of reviews.

Also, when working with PVSyst, it is important to keep a habit of recording the rationale for input values. Recording why you chose a particular weather data set, why you selected certain loss values, and why you chose specific equipment makes it easier to review later. Even if the person in charge changes, understanding the intent behind the settings can reduce rework. The quality of a simulation is determined not only by the calculation results but also by the management of the underlying assumptions.

When comparing multiple proposals, it is also important to standardize the comparison conditions. For example, if you only want to compare module capacity but the meteorological data and loss settings are changed as well, the comparison will not be valid. When creating multiple scenarios in PVSyst, make clear which items were changed and which were not. When preparing comparison materials, also ensure you can explain which conditions were held constant and which were varied so that decision-making becomes easier.

The PVSyst manual is not just material for learning how to operate the software. It is a foundational resource for understanding the meaning of settings and for being able to explain the results. In practice, applying the manual’s content to project conditions and using it as checklists and review procedures yields greater effectiveness.

Summary

To successfully perform the initial setup in the PVSyst manual, it is important not only to follow the on-screen input procedures but also to understand how each setting affects the simulation results. In particular, project conditions and site information, meteorological data, azimuth and tilt angles, modules and inverters, loss settings, and pre-report assumption checks are key items that should definitely be reviewed at the initial stage.

PVSyst is an advanced simulation software that, when used correctly, becomes a powerful tool for design studies and business feasibility assessments. However, if input conditions are incorrect, a well-presented report can still produce results that differ from reality. For that reason, verifying the initial settings should be treated not as mere administrative work but as a step that underpins the reliability of the entire simulation.

First, check the installation site and meteorological data, then review the azimuth and tilt angles, equipment conditions, and loss conditions in that order. Before generating the report, verify the consistency between the assumptions and the results. Simply making this sequence a habit can greatly reduce the common initial setup errors that occur in PVSyst.

Even if you are using PVSyst for the first time, you don't need to try to understand everything at once. While referring to the PVSyst manual, it is realistic to first cover the basic checkpoints and then increase the items you check for each project. The important thing is not just to fill in input values, but to be able to explain why you chose those values.

In solar PV simulations, not only numerical accuracy but also transparency of assumptions is required. By carefully configuring PVSyst’s initial settings and producing well-founded simulation results, you can create more reliable documentation for internal reviews, customer explanations, design comparisons, and business decisions.