What does the initial setup of PVSyst do? Explaining the first 7 items

Table of Contents

• What to decide first when initially configuring PVSyst

• Item 1: Set the project name and file-saving rules

• Item 2: Configure basic site, coordinates, and time information

• Item 3: Review meteorological data and solar radiation conditions

• Item 4: Enter system size and design conditions

• Item 5: Check photovoltaic module and power conversion equipment conditions

• Item 6: Set orientation, tilt, and layout conditions

• Item 7: Set loss conditions and perform pre-calculation checks

• Common mistakes in initial setup and how to review them

• Approach to linking on-site information with PVSyst settings

• Summary: The accuracy of the initial setup determines the quality of PVSyst utilization

What to Decide First in PVSyst Initial Settings

The initial setup of PVSyst is not simply the task of filling in fields on the screen. It is the work of organizing the planning conditions of a photovoltaic power system into a form that can be reproduced in a simulation. When using PVSyst in practice, looking only at the power generation figures is not sufficient. You need to confirm which location is being assumed, which meteorological data was used, how the system capacity was set, whether the azimuth and tilt match the site conditions, and whether the losses are neither over- nor under-estimated; only then can you explain the calculation results.

In the initial setup, what you should first be mindful of is categorizing the information you input into design conditions, site conditions, and calculation conditions. Design conditions are the information determined as part of the equipment, such as the capacity of the photovoltaic modules, the capacity of conversion equipment, the circuit configuration, the installation tilt, and the number of installation surfaces. Site conditions are information originating from the site, such as the location, latitude and longitude, surrounding terrain, shading factors, ground or roof orientation, and the area available for installation. Calculation conditions are the information treated as assumptions for the simulation, such as meteorological data, loss rates, temperature conditions, output degradation, wiring losses, soiling, and availability.

When you're just starting to learn how to use PVSyst, it can be difficult to see which items have a large impact on the results. However, the factors that particularly affect annual energy production are the site and meteorological data, the orientation and tilt, the system capacity, shading, and loss conditions. In other words, during the initial setup, simply checking these areas carefully can greatly change the reliability of the results. Conversely, seemingly simple items such as the project name or the save location are also important when comparing multiple scenarios, because as the number of simulations with different conditions increases, it becomes hard to tell which is the final option, which is for comparison, and which conditions were changed.

In this article, the initial settings of PVSyst are organized into seven items. You don't need to aim for perfect settings from the outset, but understanding what to check in each item will make it easier to revise and compare. PVSyst may seem to have many input fields when you first start using it, but once you grasp the basic workflow, you can proceed with the same approach for each project.

Item 1: Organize project names and storage rules

The first things you should set up in PVSyst’s initial configuration are the project name and the file-naming/saving rules. In generation simulations, it is common to compare multiple scenarios even for the same project. For example: changing the azimuth, changing the tilt angle, changing the system capacity, revising shading conditions, or adjusting loss rates. If you save these settings haphazardly, when you review them later you will not be able to tell which data is the most recent and which is still under consideration.

It is easier to manage if the project name includes information that indicates the project title, the site, the equipment category, the study stage, the creation date, and any differences in conditions. In practice, there are stages such as initial study, conceptual design, detailed design, revision proposals, and final confirmation, and the purpose differs even for the same project. When using PVSyst calculation results for internal review or for explaining to clients, it is important to make clear which stage of calculation they represent.

The reason for standardizing save rules is not only to help the person doing the work but also to ensure that other team members can review the files later. In the design of solar power systems, multiple people may be involved, such as surveying, layout studies, electrical design, construction planning, and power generation estimation. If PVSyst data ends up looking like an individual's personal work notes, the effort required to confirm conditions during handover increases. Conversely, if the project name and saving rules are well organized, it becomes easier to recheck simulation results and adjust conditions.

Also, at the initial configuration stage, it is important not to treat the first calculation result as the final value. PVSyst is a tool for entering conditions and viewing results, but in practice you rarely finish with a single input; you will adjust it repeatedly to reflect site information and design changes. Therefore, saving versions so that the differences between the initial proposal, the review proposal, and the revised version are clear will improve efficiency in later stages. In particular, when comparing changes such as different tilt angles or capacities, including the distinguishing characteristics of the conditions in the file names makes it easier to compare the result reports without confusion.

When learning how to use PVSyst, you tend to focus on operating the calculation screens, but in practice data management is also an important part of the initial setup. Deciding on the project name and save rules up front makes condition comparisons, internal sharing, preparation of explanatory materials, and later recalculations go more smoothly.

Item 2: Set basic information for location, coordinates, and time

One of the most important initial settings in PVSyst is the site information. The energy output of a photovoltaic system is greatly influenced by the solar irradiance at the installation site, ambient temperature, latitude, seasonal variations, and solar altitude. Therefore, if the site information is incorrect, no matter how carefully you enter the system parameters, the reliability of the simulation results will decline. Location, latitude and longitude, elevation, and time conditions are items that should always be checked first.

When specifying the site location, it is desirable to use coordinates that are as close as possible to the actual installation area, not just the address or place name of the target site. Even within the same city or municipality, conditions such as solar radiation, temperature, fog, snowfall, and surrounding shading can differ between coastal areas, mountainous regions, plains, and hilly terrain. In particular, for large-scale power generation facilities or projects installed on slopes, the way a representative point is chosen can create discrepancies with actual on-site conditions. For the initial setup, it is practical to use a point near the center of the power generation facility or a location that can represent the installation area as the reference.

Time settings are another item that's easy to overlook. The position of the sun is linked to time and affects meteorological data and shading assessments. When setting the site in PVSyst, check that the time zone and regional settings match the location. For overseas projects or projects spanning regions, discrepancies in time settings can have an impact, so it is important to verify them together with the site location information.

Elevation also indirectly affects power generation calculations. In higher-elevation areas, temperature and atmospheric conditions change, which can influence module temperature and generation efficiency. Of course, elevation alone does not determine energy output, but treating it correctly as part of the site conditions can clarify the assumptions behind the calculation. In particular, in mountainous areas, reclaimed or developed land, sloped sites, and large sites there may be elevation differences within the installation area, so it is useful to organize how representative values are determined.

When using PVSyst, entering the site settings once is not the end; it is important to later check that they do not conflict with the meteorological data or shading conditions. For example, if the site is set as flat ground but there is actually a mountain to the south, the usual solar irradiation conditions alone may not adequately capture the local shading effects. Site information is not just an address entry, but the foundation for translating the actual site into the simulation space. By configuring this carefully, the subsequent meteorological data, layout conditions, and shading assessments will become meaningful.

Item 3: Check meteorological data and solar radiation conditions

In PVSyst's initial settings, the factors that have a major impact on energy production are meteorological data and solar irradiance conditions. The annual energy output of a photovoltaic system is determined not only by system capacity but also by how much sunlight it receives. Therefore, if you proceed with calculations without understanding how to select and verify meteorological data, it will be difficult to explain the results. To master PVSyst for practical work, it is important to treat meteorological data not as mere input fields but as the fundamental data for energy production calculations.

Meteorological data involve horizontal solar irradiance, diffuse solar irradiance, temperature, wind speed, and so on. In practice, you should check the types and accuracy of the data that can be obtained, the distance to the target site, the observation period, and the concept of a representative year. Even if there is an observation point near the target site, its data do not necessarily represent the actual conditions at the installation location. This is because of local factors such as surrounding topography, sea breezes, shading by mountains, the propensity for clouds to form, snowfall, fog, and other region-specific conditions. Especially in mountainous areas or complex terrain, it is important to verify that the meteorological data are consistent with on-site, real-world conditions.

When checking solar irradiation conditions, it is important to look not only at annual values but also at monthly trends. Even if the annual energy production appears reasonable at first glance, if the monthly generation deviates significantly from the local seasonal patterns, you should review the meteorological data and shading conditions. For example, in regions affected by snow or low solar elevation in winter, areas strongly influenced by the rainy season, or regions prone to output reductions due to high temperatures in summer, confirming monthly trends is important.

Also, when configuring meteorological data, it is important not to choose overly favorable conditions. When there is an incentive to make projected energy production appear higher, solar irradiance conditions may be set optimistically. However, in practice it is important to be able to explain the validity of the calculation results, and if it later turns out they do not match the on-site conditions, it will affect the credibility of the overall design. Because PVSyst can perform detailed calculations, the more clearly the justification for the input values is documented, the more persuasive the results become.

In the initial setup, it is useful to record the reasons for selecting the meteorological data as a work memo. Making them explainable later — for example, that the data are close to the target site, have a small elevation difference, match regional characteristics, or adhere to the company’s standard conditions — will be helpful during reviews. As you become familiar with using PVSyst, you will realize that choosing meteorological data is not merely a preprocessing step but a decision that determines the quality of the simulation.

Item 4: Enter the system size and design conditions

After setting the site and meteorological data, the next step is to verify the system size and design conditions. Here you enter the overall system capacity, the number of installation surfaces, the circuit configuration, and the basic concept of the assumed power generation system. In PVSyst’s initial setup, you first create a broad outline of the installation, and then proceed to configure modules, power conversion equipment, and loss conditions in detail.

When determining the system size, don’t simply line up as many PV modules as will fit; consider site conditions, grid connection conditions, power conversion equipment capacity, maintenance access routes, shading effects, and electrical constraints. In PVSyst you can enter a capacity, but in real‑world design the area available for layout changes depending on terrain and structures, clearances, working space, slopes, drainage, and access roads. Therefore, during the initial setup stage you need to be mindful of whether the planned installed capacity is consistent with the on‑site layout plan.

In the design conditions, the relationship between DC-side capacity and AC-side capacity is also checked. Depending on how the capacity of the power conversion equipment is set relative to the total capacity of the photovoltaic (PV) modules, the power generation and the tendency for output curtailment will change. Designs that make the DC side larger may see output limited during periods of strong solar irradiance, while they can also take advantage of operation during low-irradiance periods. Because PVSyst can reflect these relationships in the simulation, it is important to be mindful of the capacity balance at the initial setup stage.

Also, when entering design conditions, not all details may be finalized from the outset. At the preliminary study stage, calculations are performed using provisional capacities and standard configurations, and as the design progresses these are updated to match the actual equipment and layout conditions. What is important here is not to confuse provisional settings with finalized ones. When checking PVSyst calculation results, you need to be aware of which items are provisional and which are finalized.

As a way of using PVSyst, entering the system size is the central step for producing the energy output, but it is also an opportunity to uncover inconsistencies in the design conditions. If, during input, the capacity balance looks unnatural, the number of circuits is unrealistic, or the number of modules seems too large for the available layout area, review the design conditions before proceeding with the simulation. By confirming such discrepancies at the initial setup stage, you can more easily prevent major rework in later steps.

Item 5: Verify the Conditions of Solar Cell Modules and Power Conversion Equipment

In PVSyst's initial setup, confirming the conditions of the photovoltaic modules and the power conversion equipment is also indispensable. In energy yield simulations, module output characteristics, temperature characteristics, converter efficiency, input range, and capacity ratio all affect the results. If these are left at rough/default settings, the simulated generation for the same installed capacity may not reflect what a real design would produce.

When configuring photovoltaic modules, pay attention not only to the rated output but also to how output changes with temperature. In solar power generation, higher solar irradiance generally increases power production, but module output tends to decrease as module temperature rises. Therefore, in regions with high ambient temperatures or in installation conditions with poor ventilation, temperature effects cannot be ignored. PVSyst can perform calculations that reflect these characteristics, so it is important to verify in the initial setup that the module conditions are appropriate.

When configuring the converter, check the compatibility of capacity, input voltage range, conversion efficiency, and circuit configuration. In practice, you need to verify that the number of modules in series and in parallel falls within the converter's allowable range and that voltage conditions at low and high temperatures do not cause problems. If errors or warnings appear in PVSyst, they may indicate a design mismatch rather than a simple input mistake. Instead of ignoring warnings and proceeding with calculations, it is important to make a habit of checking what is causing them.

Also, the combination of modules and power conversion equipment affects not only energy production but also operational aspects. Depending on how capacities are configured, the time periods when output clipping is likely to occur, the start-up behavior under low irradiance, the effects of partial shading, and the variability between circuits will change. In PVSyst’s initial settings, first perform calculations using a standard combination, and, if necessary, create simulations under different conditions to make comparisons easier.

What practitioners should be aware of when using PVSyst is not to treat equipment parameters as mere model selections. Even with the same installed capacity, differences in module characteristics or in the configuration of conversion equipment will change the energy yield and the breakdown of losses. Examining the effects of conversion losses, temperature losses, limits due to oversizing, mismatch, and so on in the calculation results makes it easier to verify the validity of the initial settings.

Item 6: Set orientation, tilt, and placement conditions

In PVSyst's initial setup, orientation, tilt, and layout conditions are extremely important. The amount of solar irradiance a photovoltaic system receives changes depending on the direction and angle at which it is installed relative to the sun's movement. In particular, for fixed installations, orientation and tilt directly affect annual energy production. Because roof-mounted, ground-mounted, and slope-mounted installations have different conditions, inputs must be tailored to the on-site installation plan.

When setting the orientation, check that the direction on the drawings matches the actual direction on site. Even if the design appears neatly south-facing, the actual site may be slightly rotated to fit road boundaries, topography, grading direction, or building shape. A difference of a few degrees does not necessarily change the results greatly, but for equipment with multiple faces or east–west layouts, differences in orientation settings will affect the power generation curve.

The same applies to the tilt angle. The tilt angle is related to annual energy production, seasonal generation trends, the effects of snow and soiling, wind loads, constructability, and so on. In PVSyst you can input the angle, but in practice there are trade-offs with mounting conditions, roof pitch, terrain slope, and maintainability. In initial settings, you should not simply look for the angle that seems to maximize energy production; you also need to consider whether that angle is actually constructible and easy to maintain.

In layout planning, check the spacing between module rows, the subdivision of the mounting surface, surrounding obstructions, inter-row shading, and terrain-related shading. In particular, for ground-mounted installations, narrow row spacing makes shadows from the front rows more likely to fall on the rear rows in winter and at dawn and dusk. If you look only at energy output you may be tempted to increase system capacity, but if row spacing is too tight shading losses increase and the expected energy production may not grow as much as anticipated. When using PVSyst, an effective workflow is to compare a proposal that increases capacity with one that suppresses shading losses and judge which is more practical.

Also, when there are multiple installation surfaces, it is necessary to adopt the approach of setting each orientation and tilt separately. If each roof plane faces a different direction or the site is divided into multiple blocks to match the terrain, summarizing the whole under a single condition can diverge from reality. Simplification may be acceptable in initial assessments, but in detailed studies reflecting the conditions of each installation surface as much as possible will increase the explanatory power of the results.

Item 7: Perform Loss Conditions and Pre-Calculation Checks

The final items to check in PVSyst’s initial setup are the loss conditions and the pre-calculation checks. In solar power simulations, not all of the incident solar irradiance is converted into electricity. Energy production is reduced by various factors such as temperature rise, wiring resistance, conversion losses, soiling, shading, variability in equipment characteristics, degradation over time, downtime, and power curtailment. Because PVSyst treats these as losses, it is important to verify them accurately—without under- or over-estimation—at the initial setup stage.

What to be careful about with loss conditions is not to use standard values as-is but to consider whether they fit the characteristics of the project. For example, in areas with a lot of dust, locations heavily affected by birds, regions with snowfall, sites near the sea, places with many surrounding trees, or sites where maintenance frequency is limited, the way you account for soiling and temporary reductions in power generation changes. Conversely, for installations with well-established maintenance systems where cleaning and inspections are easy, applying overly conservative losses can lead to underestimating power generation.

Wiring losses and conversion losses are related to electrical design. Losses vary depending on cable length, cross-sectional area, circuit configuration, and the placement of conversion equipment. In the early stages, approximate values may be used, but as you move into detailed design, those values need to be revised to match the actual wiring plan. By checking the loss breakdown in PVSyst's calculation results, you can identify which losses are largest. If losses are larger than expected, this prompts a review of the design conditions and input values.

In the pre-calculation check, confirm the consistency of the input values. Verify that the site location and meteorological data are correct; that the system capacity matches the installation area; that the orientation and tilt match the drawings; that there are no warnings in the equipment settings; that the shading settings reflect on-site conditions; and that the loss assumptions are not excessively high or low. While you may be eager to view the results screen until you become familiar with PVSyst, carefully performing these pre-calculation checks will reduce the time spent later troubleshooting unexplained discrepancies.

In the initial setup phase, it may not be possible to determine all losses completely. In that case, it is practical to make it clear that they are provisional settings and to leave them as items to be reviewed later. The important thing is not to simply enter loss values and be done, but to be in a position to explain the reasons for adopting those values.

Common Mistakes in Initial Setup and How to Review

A common mistake in the initial setup of PVSyst is refining only some input values in detail while overlooking the overall consistency. For example, module and inverter parameters may be set carefully while site and meteorological data remain at an approximate level. Also, being overly focused on increasing system capacity can lead to insufficient consideration of inter-row shading and maintenance space. Because PVSyst handles many conditions, making only one aspect accurate while other assumptions remain vague does not increase the reliability of the results.

Another mistake is treating the initial settings and the simulation results as separate. If the power generation is higher or lower than expected, you should not simply accept the result; you need to check which settings are affecting it. Looking at monthly generation, the breakdown of losses, shading losses, temperature losses, conversion losses, and so on makes it easier to find where a setting feels off. Checking the results is also a way of verifying the initial settings.

Also, be careful when reusing settings from past projects. As you become familiar with PVSyst, you may duplicate a previous project and use it for a new one. This approach is efficient, but there is a risk of forgetting to change items such as location, meteorological data, capacity, azimuth, tilt, loss conditions, and the saved file name. Be especially cautious with items that appear to calculate correctly at first glance. When reusing settings, first check the project-specific items and review whether any previous conditions remain.

When reviewing initial settings, it is important not to judge solely by the energy production figures. Even if the annual energy production falls within the expected range, monthly trends or the breakdown of losses may be inconsistent. Conversely, even if the annual value is lower than expected, it may be a reasonable result if the site has strong shading or high-temperature conditions. PVSyst results should be evaluated not as standalone numbers but together with the input conditions.

As a practical review method, it’s easiest to follow the sequence of first checking the site and meteorological data, then the system capacity and orientation/tilt, and finally the shading and loss conditions. By checking the items that have the greatest impact on energy production first, you can more efficiently identify the cause. Before diving into detailed settings, verifying that the major assumptions are correct is the basic principle for using PVSyst in practice.

Approach to Linking Site Information and PVSyst Settings

To make PVSyst's initial settings useful in practice, it is important how accurately you can reflect on-site information in the simulation conditions. PVSyst is a powerful tool for calculating power generation, but it does not automatically understand the site. The installation area, topography, azimuth, tilt, obstructions, shading, elevation differences, and surrounding environment need to be organized from on-site surveys, drawings, and survey data and reflected as input conditions.

When site information is lacking, the initial settings will be provisional. The energy production obtained under these conditions is only a guideline for preliminary assessment. As on-site surveys and design progress and more accurate layout and topographic information become available, the PVSyst parameters should be updated. Assuming this update process in advance makes the transition from preliminary to detailed assessment smoother. As a way to use PVSyst, it is practical to first confirm the overall direction with rough conditions and then incorporate site information to improve accuracy.

Particularly important are information on orientation, tilt, and shading. These can vary greatly depending on site conditions. Even with the same installed capacity, the expected power generation outlook differs between a flat site with few obstacles and a sloped site with surrounding trees and buildings. When shading factors are present, you must not simply look at solar irradiation data; you need to determine on site when, from which direction, and over what extent shadows will fall.

Also, the accuracy of on-site information affects post-construction management. If the design-phase conditions and the actual installation positions diverge, comparing simulation results with actual power generation becomes difficult. When analyzing differences in power output—whether they are due to weather variations, shading effects, differences in installation angle, or incorrect assumptions about loss conditions—you need a basis for the initial settings.

In this sense, the initial settings of PVSyst cannot be completed by desk work alone. Properly handling location information and terrain data obtained on site and linking them to design data increases the value of simulations. When considering power generation facilities, the accuracy of positioning and assessment of current site conditions directly affects layout planning, shading analysis, and construction management. Those using PVSyst should always be aware not only of the input fields on the screen but also of the on-site conditions behind them.

Summary: The accuracy of initial settings determines the quality of PVSyst use

The seven items you should check first in PVSyst’s initial setup are the project name and saving rules, site/location and coordinates and time, meteorological data, system size, PV modules and conversion equipment, orientation, tilt and layout conditions, and loss conditions. These may appear to be independent input items, but in reality they are interrelated. If the site changes, the meteorological conditions change; if the orientation or tilt changes, the way solar radiation is received changes; if the layout changes, the appearance of shading and losses changes. The important point when using PVSyst is not to fill in each item independently, but to arrange them so they form a consistent set of conditions as a whole.

Careful initial setup gives the power generation figures credibility. You will be able to explain why the generation came out as it did, which conditions influenced the results, which items are provisional settings, and which items are confirmed conditions. This is useful for internal approvals, customer explanations, design comparisons, pre-construction reviews, and post-operation performance comparisons. Conversely, if the initial settings remain vague, it becomes difficult to explain the basis for the results when they appear, and it takes extra effort to review the conditions later.

PVSyst is a practical tool for numerically evaluating plans for solar power generation. However, to produce reliable simulations, organizing on-site information is indispensable in addition to operating the software. In particular, the more accurately you can determine the installation location, terrain, orientation, tilt, and shading factors, the closer PVSyst’s initial settings will be to reality. Correctly measuring site conditions and linking them to design parameters leads to improved accuracy of energy yield simulations.

When planning or managing the construction of photovoltaic power systems, if you want to obtain high-precision location information on site, using LRTK (an iPhone-mounted GNSS high-precision positioning device) can streamline the acquisition and recording of on-site coordinates. As a preliminary step before evaluating energy yield in PVSyst, accurately understanding the installation area and site conditions helps with layout planning, shadow assessment, and post-construction management. To configure PVSyst initial settings under conditions closer to actual practice, it is important to combine simulation with on-site surveying.