6 Steps to Start Power Generation Simulation with the PVSyst Manual

Table of Contents

• Overview to Understand Before Reading the PVSyst Manual

• Step 1: Organize the project conditions and determine the purpose of the simulation

• Step 2: Create the project and set the location information

• Step 3: Select meteorological data and set the assumptions for power generation calculations

• Step 4: Set up the modules and power conditioner

• Step 5: Incorporate azimuth, tilt angle, shading, and loss conditions

• Step 6: Interpret the simulation results and use them to make improvements

• Common Pitfalls in the PVSyst Manual

• Precautions when using power generation simulations in practical work

• Summary

Overall picture to understand before reading the PVSyst manual

Many people searching for a PVSyst manual want to start simulating the energy yield of a photovoltaic installation, but they are unsure which screen to enter data on, which parameters to decide first, and where to look in the results report. PVSyst is a specialized simulation software used for PV system design, energy yield forecasting, loss analysis, and report generation, and rather than simply entering the system capacity and expecting correct results automatically, it is important to build up the consistency of input conditions step by step.

The official PVsyst Version 8 tutorial covers the design procedures for grid-connected projects, parameter settings, energy balance calculations, and analyses that take site conditions and losses into account. Furthermore, Project design and simulation is described as the central function for project evaluation, performing annual simulations that include meteorological data, system design, shadow analysis, loss settings, and economic assessment.

What matters here is understanding the flow of the energy-yield simulation before reading the PVSyst manual in detail from start to finish. In practice, checking in the order of site, meteorology, equipment configuration, installation angle, shading, various losses, and output results makes it easier to spot missing inputs or contradictory conditions. Conversely, if you merely follow the screen order, you won’t understand why each item is entered and will be unable to assess the validity of the results.

Power generation simulations in PVSyst are not a process that yields the correct design in a single attempt. First you calculate under standard conditions, then you adjust shading, losses, equipment configuration, installation angle, and so on while comparing multiple design options. The PVSyst project tutorial also recommends running a new simulation at each step and, in particular, checking the effects by analyzing the Loss diagram.

This article explains the workflow of energy yield simulation in six practical steps so that even readers approaching the PVSyst manual for the first time can grasp it. The explanation is organized around the concepts that are commonly important across projects, without relying too much on specific screen names or version differences.

Step 1: Organize the project conditions and decide the purpose of the simulation

Before opening the PVSyst manual, the first thing you should do is clarify the purpose of the simulation. Whether you want to estimate energy production, compare design proposals, or prepare supporting documentation for financial institutions or internal approval processes will change the required input accuracy and the items you need to verify. If you start entering conditions into PVSyst while the purpose is unclear, you may later lose track of what decisions the results were meant to inform, which leads to more re-entry and recalculation.

First, what we need to sort out are the basic project details. Confirm the assumptions such as the installation location, the expected system capacity, whether it is ground-mounted or roof-mounted, whether it is self-consumption type or full-feed-in type, whether it includes batteries, and whether there are any grid-connection conditions. In generation simulations, these conditions affect not only the generation amount but also losses, output curtailment, PCS capacity, wiring design, and the impact of shading. For example, even with the same module capacity, roof-mounted and ground-mounted installations cannot be compared using the same input values because tilt angle and orientation, shading, temperature conditions, and maintenance conditions differ.

Next, determine which stage of the study you are at. For an initial study, an approximate plant capacity and standard loss conditions may be sufficient. In contrast, at a stage closer to detailed design, you need to make module type, PCS type, string configuration, tilt angle, azimuth, shading, wiring losses, soiling, temperature conditions, and so on closer to reality. When you read the PVSyst manual you will find many input items, but you do not need to decide every item strictly from the outset. What matters is judging, according to the study stage, how accurately you should input things now.

Also, in power generation simulations it is essential to keep the input conditions in a state where they can be explained later. If you cannot explain why you used a particular meteorological dataset, why you adopted a certain loss rate, or why you chose a specific tilt angle, the reliability of the results will be reduced. While PVSyst can produce detailed calculation results, if the input conditions are inappropriate it can result in a report that only looks superficially well-prepared. Organizing the project conditions at the initial stage and making notes of the rationale for the inputs will greatly affect the quality of subsequent processes.

Step 2: Create the project and set the location information

After organizing the project conditions, create a new project in PVSyst. For energy yield simulations, the site information set when creating the project is extremely important. Because the energy output of a solar power system is affected by solar irradiation, temperature, latitude and longitude, elevation, and the surrounding environment, if the installation site is inaccurate, the reliability of the results will decrease regardless of how precisely the equipment configuration is adjusted later.

When creating a project, first give it a clear, descriptive name. In practice, because multiple design proposals for the same project are often compared, it is easier to manage if the project name, installation location, date of analysis, and proposal type are clearly indicated. For example, when creating proposals that change the tilt angle, change the PCS capacity, or add shading conditions, ambiguous naming can make it impossible to tell which result is the latest.

Next, enter the site information. Latitude, longitude, elevation, and time zone affect the power generation calculation. Pay particular attention for overseas or wide-area projects, as site mix-ups are likely. Even within the same prefecture or municipality, meteorological and shading conditions can differ between mountainous, coastal, and urban areas. Even when working with the PVSyst manual, do not rely solely on the on‑screen input; it is important to cross-check the planned installation site’s coordinates and terrain conditions against separate documents.

After setting the site information, understand the project's basic conditions and the concept of system variants. In PVSyst, you can manage multiple design proposals within a single project. This makes it possible to compare cases using the same site conditions while varying module capacity, PCS capacity, installation angle, shading conditions, loss conditions, and so on. Instead of drawing conclusions from a single proposal from the start, creating the project with comparison in mind greatly improves the usability of the energy yield simulation.

In practical work, it's easiest to proceed by first creating a baseline plan and then adding improvement and verification plans. In the baseline plan, avoid introducing unnecessarily complex conditions and perform calculations using the basic site, weather, equipment, and installation angle. Using those results as the reference, compare cases such as adding shading, changing the tilt angle, or revising the PCS capacity. This approach makes it easier to understand how much each condition affected power generation.

Step 3: Choose meteorological data and establish assumptions for power generation calculation

When running energy yield simulations in PVSyst, selecting the meteorological data is one of the most important tasks. The energy output of photovoltaic systems is strongly influenced by solar irradiance and ambient temperature. Therefore, which meteorological data you use will affect the annual energy yield, monthly energy yield, performance ratio, and loss analysis results. When reading the PVSyst manual, you will find many sections related to meteorological data, but beginners should first understand that "meteorological data are the foundation of energy yield predictions."

When selecting meteorological data, confirm that it is data close to the installation site, that it suits the purpose of the analysis, and that it can be explained as an input condition. Solar radiation data come in various types, such as monthly averages, hourly data, satellite-derived data, and station-observed data. Rather than assuming any one is absolutely correct, you need to choose the appropriate type based on the project scale, study phase, and required accuracy. Standard data may be used in preliminary studies, but in detailed studies you should select data that are closer to the site or that have greater validity.

When examining meteorological data, it is important to check not only solar irradiance but also temperature. Solar modules lose output when they become hot, so temperature conditions affect energy production. In hot regions, temperature losses tend to be large, while in cold regions handling snow and low-temperature conditions can be problematic. When calculating energy production with PVSyst, even if the annual solar irradiance is high, actual production may be limited by conditions such as high temperature, shading, soiling, or snow.

Also, attention must be paid to the units and period of the meteorological data. If you judge based only on annual values, you will overlook monthly generation trends and seasonal variations. For example, generation profiles vary by location — regions where solar irradiance is high in summer but high-temperature losses are also large, regions where irradiance is low in winter but temperature conditions are favorable, and regions strongly affected by the rainy season or snowfall. To interpret PVSyst results, you need to check what kind of seasonal variation the input meteorological data has.

After selecting the meteorological data, verify its consistency with the project conditions. Check whether the installation site and the meteorological station are far apart, whether the elevation difference is too large, and whether differences between coastal and inland locations have been overlooked. Even if you enter data following the PVSyst manual procedures, if the choice of source data is inappropriate, the simulation results will diverge from reality. Meteorological data should be treated carefully, not merely as an input item but as a prerequisite for power generation forecasts.

Step 4: Configure the modules and power conditioner

After setting the meteorological data, next set the solar modules and power conditioners. This step is the core of the power generation simulation. Module capacity, conversion efficiency, temperature characteristics, PCS capacity, input voltage range, string configuration, and so on affect the system’s overall energy production and losses. Even if you proceed while checking the equipment-configuration screen in the PVSyst manual, you must verify that the chosen model from the database actually matches the real design conditions, rather than simply selecting it.

First, select the solar module. The module’s nominal output, number of modules, installed capacity, temperature coefficient, and voltage-current characteristics are reflected in the power generation calculations. Even with the same installed capacity, temperature losses and behavior under low irradiance can vary depending on the characteristics of the modules used. In preliminary assessments, calculations may be performed using representative module conditions, but in detailed design it is preferable to use conditions that closely match the specific models intended for adoption.

Next, configure the power conditioner. The PCS is the device that converts the DC power generated by the modules into AC, and its capacity, efficiency, input voltage range, and MPPT configuration affect energy production. If the PCS capacity is too small, clipping may occur, where output is curtailed during periods of strong irradiance. On the other hand, increasing PCS capacity is not necessarily always advantageous; you also need to consider the balance with equipment cost and operating conditions. In PVSyst, you can compare design proposals while checking such capacity ratios and conversion losses.

String configuration is also important. Check whether the number of modules in series and the number in parallel fall within the PCS input range, whether the open-circuit voltage at low temperatures does not exceed the upper limit, and whether the operating voltage at high temperatures does not fall below the lower limit. If a warning appears in PVSyst, do not simply proceed with the calculation; review the design conditions. Inconsistencies in string configuration affect not only energy yield but also safety and constructability, so it is worth verifying them early during the energy yield simulation stage.

When configuring modules and the PCS, you need to be careful about how system capacity is presented. Confusing DC capacity with AC capacity can lead to errors in estimating energy generation and interpreting performance ratios. In photovoltaic power generation, the reference may be the DC capacity on the module side or the AC capacity on the PCS side. When explaining PVSyst results internally or externally, it is important to clarify which capacity is being used as the reference. Leaving this ambiguous when making comparisons will cause discrepancies in kWh/kW and capacity utilization assessments.

Step 5: Reflect azimuth, tilt angle, shading, and loss conditions

Once you have configured the equipment, reflect the installation conditions and loss parameters. This step is one of the parts of the PVSyst manual where practical differences frequently arise. In energy yield simulations, even when using the same modules and PCS, results can vary greatly depending on azimuth, tilt angle, surrounding shading, wiring losses, soiling, temperature, mismatch, conversion losses, and so on. In other words, how closely you can match these to the actual site conditions determines the quality of the simulation.

First, check the azimuth and tilt angles. It is not sufficient to rely on the simple notion that the closer a system faces south the higher the energy production will be. Depending on the project, the way you think about the optimal angle changes—for example, when prioritizing morning and evening generation, matching the roof shape, minimizing racking costs, or accounting for snow and wind loads. In PVSyst you can create multiple scenarios with different angles and compare changes in annual generation, monthly generation, and losses. For initial studies it is convenient to calculate using representative angles, and for detailed studies to set the angles according to design drawings and site conditions.

Next, check the shading conditions. Shading includes horizon shading caused by distant mountains or buildings, and near-field shading from adjacent buildings, trees, between rows of mounting structures, rooftop equipment, and so on. The effects of shading relate not only to reduced energy generation but also to nonuniformity and mismatch at the string level. If shading is underestimated, simulations may show higher energy output while actual operation could fall short of expectations. It is especially important not to neglect verification of shading conditions for rooftop installations and projects with complex terrain.

Loss conditions should also be set carefully. In PVSyst, multiple losses—temperature loss, wiring loss, module quality loss, mismatch loss, soiling loss, IAM loss, PCS loss, and others—are reflected in the energy production. Beginners may find this difficult because there are many loss items, but it becomes easier to understand if you think of it as “how much reduction that occurs in real power generation equipment you should anticipate.” The energy production calculated under ideal conditions differs from the energy production calculated under conditions closer to reality. By appropriately including losses, you get closer to a more realistic energy production forecast.

However, it is not necessarily better to assume excessive losses. Stacking unsubstantiated conservative settings can lead to overly cautious estimates of power generation and may result in a misjudgment of a project. Conversely, conveniently underestimating losses increases the risk in the business plan. What matters is being able to explain the rationale for each loss. You should take a stance of selecting reasonable values based on past performance, design conditions, site environment, maintenance policies, manufacturer documentation, internal standards, and so on.

Step 6: Interpret Simulation Results and Use Them to Make Improvements

After setting the conditions, run the simulation and interpret the results. PVSyst produces various figures in report format, but what beginners should look at first are the annual energy production, monthly energy production, performance ratio, loss diagram, and the system's warnings or inconsistencies. It is important not to stop at just the energy production numbers, but to verify why those results occurred.

Annual power generation is a basic indicator for understanding the expected generation of the entire project. However, the annual figure alone does not reveal seasonal variations or problems in specific months. By looking at monthly generation, you can determine whether high-temperature losses are significant in summer, whether solar irradiance is low in winter, whether generation drops during the rainy season, or whether the effects of snow and shading are likely to appear. For business planning and evaluating self-consumption, monthly and time-of-day generation trends can be important in addition to the annual total.

Performance ratio is an indicator for assessing how efficiently a system generates electricity relative to solar irradiance conditions. If the performance ratio is extremely low, check whether there are problems such as shading, temperature, wiring, PCS, string configuration, or loss settings. Conversely, if the performance ratio is too high, caution is also necessary. The input conditions may be more favorable than reality—for example, losses are insufficiently accounted for, shading is not reflected, or the meteorological data are overly optimistic.

The Loss diagram is particularly important when reviewing PVSyst results. By looking at the loss diagram, you can see at which stages and by how much losses occur from solar irradiance to the final AC output. If you can determine whether shading loss, temperature loss, PCS loss, or wiring loss is large, you can identify directions for design improvement. Rather than simply concluding that "power generation is low," it is important to analyze "which loss is causing the low output."

After reviewing the simulation results, improvement proposals are developed. For example, possible measures include changing the tilt angle, revising the azimuth, modifying the PCS capacity, adjusting the string configuration, arranging the layout to avoid shading effects, and reducing wiring losses. Because PVSyst allows creating multiple variants, the standard proposal and improvement proposals are compared while comprehensively evaluating energy yield, losses, and the feasibility of the design. The proposal that produces the maximum energy yield is not always the optimal one. Decisions must be made taking into account a balance of constructability, cost, maintainability, grid conditions, and site constraints.

Common Pitfalls in the PVSyst Manual

Even when working while reading the PVSyst manual, many people stumble over the same points. The most common issue is proceeding without understanding the meaning of the input fields. PVSyst is specialized software, and the items displayed on the screen are directly tied to the assumptions used in energy production calculations. Leaving unknown items at their default values is not inherently wrong, but using those defaults without checking whether they suit your project makes it difficult to explain the results.

The next common stumbling block is managing projects and variants. When you create multiple proposals for the same project, you can lose track of which is the standard plan, which is the shaded variant, and which is the final plan. To prevent this, it is effective to include the conditions in each proposal's name and to record the changes made. Power generation simulations are not a one-time task but an iterative process of comparison and revision. Simply using clear, easy-to-manage names and leaving notes makes it much easier to trace results later.

Handling weather data can be confusing. Even if you think you have selected data close to the installation site, the elevation or regional characteristics may not match. Also, if you use data without being aware of its source or time period, it becomes difficult to explain the basis for the results. The reliability of power generation simulations is heavily dependent on the validity of the weather data. It is desirable not only to check the procedures in the PVSyst manual but also to document in the project records why that data was adopted.

Loss conditions are another area where beginners often get confused. Because there are many loss items, it can be difficult to judge how much to enter. However, losses are necessary elements to represent real power generation facilities. If you completely ignore soiling, temperature, wiring, PCS, shading, mismatch, and so on, generation estimates tend to be overly optimistic. Conversely, if you set everything overly conservatively, you may underestimate a project's profitability more than necessary. What is important is to make reasonable settings appropriate to the project stage and to document the rationale.

Care is also needed when interpreting the result report. If you judge based only on annual energy production, you may overlook design issues. It is important to comprehensively check the Loss diagram, monthly energy production, performance ratio, warning indications, and whether clipping occurs. In particular, if the output results are better than expected, you should suspect that you may have forgotten to include shading or other losses. Simulation results are not complete once the numbers are produced; they only become usable documents after you verify their validity against the input conditions.

Precautions when using power generation simulations in practice

When using PVSyst's power generation simulations in practice, it is important not to accept the software's results as the final conclusion, but to organize them into a form that can be used for project decision-making. If you prepare so that energy production, performance ratio, losses, and design conditions can be explained together, it will be easier to use for internal reviews, customer presentations, materials for financial institutions, and consideration of design changes.

First, it should be noted that simulation results are based on assumptions. Power generation varies depending on weather data, equipment configuration, installation angle, shading, and loss conditions. Therefore, rather than presenting the results alone, you must clearly state under which conditions the results were calculated. In particular, when comparing multiple scenarios, it is important to separate and explain the conditions that were changed from those that were kept fixed. If all conditions change at once, you cannot tell which factor affected the power generation.

Next, verify consistency with on-site surveys and design drawings. Even if shadows and layouts are set in PVSyst, if local buildings, trees, utility poles, surrounding terrain, rooftop equipment, or potential future obstructions are not reflected, the actual power generation may differ. Simplification may be acceptable in preliminary assessments, but in detailed studies cross-checking with on-site information is essential. In particular, shading conditions can be difficult to judge from drawings alone, so combining photographs, survey data, 3D models, and on-site inspections improves accuracy.

Also, it is important to use PVSyst results as input for design improvements. When the energy yield is low, rather than simply changing conditions to favorably increase the numbers, analyze the causes of the losses and consider realistic countermeasures. If shading losses are large, review the layout and spacing; if temperature losses are large, check the racking conditions and ventilation; if PCS clipping is large, consider the DC/AC ratio; if wiring losses are large, review the wiring plan. Simulations should be used to improve design decisions, not to generate numbers.

Finally, attention should be paid to how the results are presented. For experts, detailed loss analyses and the rationale for settings are required, but for decision-makers it is important to clearly show annual energy production, the main expected losses, differences between comparative options, and the reasons for the chosen option. When staff who understand the PVSyst manual translate technical calculation results into language that can be used for practical decision-making, the value of the simulation increases.

Summary

When starting a power generation simulation in the PVSyst manual, simply memorizing the screen operations in order is not enough. It is important to first clarify the project conditions and objectives, create the project, prepare the site information and meteorological data, configure the modules and power conditioners, and—after incorporating azimuth, tilt angle, shading, and loss conditions—understand the workflow for analyzing the results.

What is particularly important is to treat PVSyst results not as "the answer for energy production" but as "material for design decisions based on the input conditions." If the meteorological data changes, the results change; if the shading or loss settings change, the energy production changes. For that reason, you need to be able to explain which conditions were adopted, why those values were chosen, and which parts of the results should be paid attention to.

The fundamentals of energy-yield simulation are to create a baseline case, check losses and shading, compare improvement scenarios, and thereby approach reasonable design conditions. When reading the PVSyst manual, rather than rote-memorizing detailed operations, deepen your understanding by focusing on how each input item affects energy production. By examining annual energy yield, monthly energy yield, the performance ratio, and the Loss diagram together, you can carry out analysis that leads to design improvements instead of merely verifying numbers.

If you are going to start an energy yield simulation in PVSyst, it is recommended to first create a small baseline case and then proceed in the order of meteorology, equipment, installation angle, shading, losses, and result checking. In addition, by changing one condition at a time and comparing multiple cases, you will find it easier to connect the contents of the PVSyst manual to practical work. Energy yield simulation, with correct inputs and careful result verification, becomes a powerful means to improve the design quality and explanatory power of solar power projects.