Five Basics for Solar PV Design Without Getting Lost in the PVSyst Manual

PVsyst is a specialized software used for design studies, system sizing, energy production simulation, and loss assessment of photovoltaic power generation systems. In this article, to match the notation commonly used in searches, it will mainly be written as PVSyst in the body of the text.

When working on the design of a solar power plant or running power generation simulations, even if you open the PVSyst manual or the official help, you may be unsure where to start looking.

There are many settings and a lot of specialized terminology, so trying to understand everything from the beginning can actually make it easier to lose sight of the overall picture of the work.

The important thing is to grasp the basic workflow—design conditions, meteorological data, equipment settings, loss conditions, and result verification—before learning detailed operations. This article, aimed at professionals who use the PVSyst manual in practice, lays out five basic points in solar PV design that are easy to get confused about.

Table of Contents

• Read the PVSyst manual not as an operating procedure but as a checklist for design conditions

• Basic 1: Firmly establish the project conditions and design objectives first

• Basic 2: Align the meteorological data and installation conditions with the on-site conditions

• Basic 3: Verify the module and PCS settings in accordance with the specifications

• Basic 4: Set the loss conditions to reflect the actual conditions at the site

• Basic 5: Do not judge the results screen based only on energy production

• How to proceed with checks to apply the PVSyst manual in practice

• Summary: A trouble-free solar design starts with organizing the conditions

Read the PVSyst manual as a confirmation document for design conditions, not as operating instructions.

When reading the PVSyst manual, the first thing to keep in mind is not to treat it merely as a step-by-step guide to button operations, but as a resource for verifying the design conditions of a solar power plant. Simulation software displays calculation results based on the conditions entered. Therefore, even if you can complete the settings on the screen, if the input conditions deviate from the actual site conditions or the design intent, the output results will be difficult to use as-is for practical decision-making.

In solar design, many factors are involved, such as expected power generation, system capacity, installation tilt, azimuth, shading effects, wiring losses, equipment conversion efficiency, and temperature-related losses. The PVSyst manual describes the meaning of each item and how to enter them, but what is important in practice is understanding which items can potentially affect the results and how. The goal is not merely to fill in input fields, but to be in a position to explain the design conditions.

A person handling it for the first time tends to try to read the manual from the beginning in order and often gets hung up on terminology and formulas along the way. However, in practice it is not necessary to understand every item with equal weight. First grasp the flow of the project's location, system size, module layout, PCS configuration, loss conditions, and how to interpret the results, and then delve deeper into the necessary sections — that approach makes it easier to proceed.

Also, when reading the PVSyst manual, it is important to compare it with the design standards used internally and the assumptions specified by the client. The general explanations in the manual are not necessarily the same as the configuration settings required for actual projects. For example, the handling of tilt and azimuth angles, the consideration of snow and soiling, the scope of shading analysis, and the set values for electrical losses should be verified with supporting evidence for each project.

In other words, to avoid getting lost in the PVSyst manual, it’s important to read it according to the flow of design decisions rather than being guided by the sequence of screens. Being able to explain which conditions you entered and why you chose those values leads to solar PV designs that are usable in practice.

Basic 1: Firmly establish the project conditions and design objectives at the outset

The basic things to confirm first in solar design are the project conditions and the design objectives. Even when working while referring to the PVSyst manual, if you begin configuring settings while the project's purpose is unclear, your judgments can easily shift midway. The scope of checks required varies depending on whether you want to estimate power generation, compare designs, prepare briefing materials for financiers or clients, or perform a final verification before construction.

In the initial study phase, the focus is on grasping the expected power generation and equipment capacity. In this case, it is more important to organize the installable area, assumed module capacity, local meteorological conditions, and approximate azimuth and tilt angle than to detail precise wiring conditions or fine shading characteristics. Conversely, when the work is to be used for detailed design or pre-contract verification, it is necessary to check more specifically the module model, PCS configuration, series/parallel counts, cable conditions, effects of shading, maintenance conditions, and so on.

In PVSyst settings you work through the project, the site, the meteorological data, and the system configuration in sequence, but in practice preparing the project details beforehand makes the work more stable. By confirming in advance the site's address and latitude/longitude, the orientation and tilt of the installation surface, any land or roof constraints, the conditions at the connection point, and the expected operational period, you will be less likely to hesitate when entering data on the screen.

Also, when the design objective is unclear, it affects how the results should be interpreted. The output metrics to focus on differ depending on whether you only want annual generation or want to check monthly generation trends. If you want to assess the impact of oversizing, you need to check the times when the PCS limits output and how losses manifest. When evaluating the effects of shading, check not only simple annual values but also how losses manifest by time of day and by season.

The important thing here is to document the design intent in writing. For example, "This simulation is for preliminary study and was created to confirm the approximate annual power generation" or "This simulation is for checking conditions before detailed design and reflects equipment specifications and layout conditions." Making the purpose clear in this way will reduce misunderstandings when reviewing the results later.

Before consulting the PVSyst manual for setup instructions, the first step to a well-directed solar design is to decide what you are performing the simulation for. Clarifying the conditions before you begin interacting with the interface is the foundation that supports the reliability of the results.

Basic 2: Align meteorological data and installation conditions with local conditions

Next, it is important to verify the meteorological data and installation conditions. In photovoltaic simulations, meteorological conditions such as solar irradiance and ambient temperature affect power generation. Depending on the data and settings used, conditions like wind speed may also be relevant to temperature calculations and thermal assumptions. When checking how meteorological data are handled in the PVSyst manual, it is important not only to decide which data to use but also to assess how well that data represents the local site conditions.

The power output of a solar power plant varies by region even with the same installed capacity. Areas with high solar irradiance and those with low irradiance show different annual generation trends, and in regions with high ambient temperatures, losses due to increased module temperature can be significant. In addition, generation trends change depending on the surrounding environment—such as mountainous areas, coastal areas, snowy regions, and urban areas. Therefore, when selecting meteorological data, it is desirable not simply to choose data from the nearest point but also to consider topography, elevation, and the surrounding environment.

For installation conditions, the azimuth and tilt angles are fundamental. Even if the layout is close to south-facing, the actual site shape, roof geometry, racking arrangement, walkways, and surrounding equipment may prevent achieving the ideal orientation. When configuring while referring to the PVSyst manual, it is important to check the input units for azimuth and tilt angles, the sign convention, and the definition of the mounting surface. If these are handled incorrectly, the way the results appear can change significantly.

Also, for installation conditions, confirm whether the system is fixed or tracking, and whether it has a single mounting surface or multiple mounting surfaces. For rooftop installations, the orientation and tilt may differ for each roof surface. Even for ground-mounted installations, slight differences can occur from row to row depending on site elevation differences and grading conditions. In practice, dividing everything too finely makes management difficult, while consolidating too much into representative conditions can diverge from actual site conditions. How far to subdivide should be determined according to the design objectives and the required level of verification accuracy.

Furthermore, the treatment of surrounding shading is also an important aspect of site conditions. Buildings, trees, slopes, adjacent equipment, utility poles, signs, and mountain shadows can all affect power generation. Because the impact of shading varies by season and time of day, you cannot judge simply by “there is shade” or “there is no shade.” When reviewing the shadow-related explanations in the PVSyst manual, it is important to consider how far shadows are modeled, how near-field and far-field shading are treated, and how the shading conditions you input are reflected in the results.

Meteorological data and installation conditions are the entry point for a simulation. If these are set inconsistently with on-site conditions, even carefully adjusting equipment settings and loss parameters later will reduce the overall validity of the results. When using the PVSyst manual, it is important to first reconcile local information with the installation conditions and proceed while documenting the rationale for the input values.

Basic 3: Verify that the module and PCS settings conform to the specifications

One area where many people responsible for solar design become uncertain is the configuration of modules and PCS. Because PVSyst often treats the equipment equivalent to PCS as an inverter, even if you use the term PCS in internal documents, confirming how it corresponds to the terminology in the manual can prevent confusion. The PVSyst manual outlines the flow for selecting modules and inverters and setting the number of modules in series, the number of strings in parallel, the capacity ratio, and so on. However, in practice you should not judge only by whether something can be selected on the screen; you need to verify that the specifications of the equipment you will actually adopt are consistent with the design conditions.

In module settings, parameters such as rated output, open-circuit voltage, short-circuit current, maximum power operating voltage, maximum power operating current, and temperature coefficients are important. These values relate not only to power generation but also to the number of modules connected in series and the combination with the PCS. In particular, voltage rise at low temperatures and voltage drop at high temperatures are key design checkpoints. By confirming that the series string voltage does not exceed allowable limits at low temperatures and that high temperatures do not push the PCS outside its operating voltage range, you can more easily assess both safety and power generation performance.

In PCS settings, check the rated capacity, input voltage range, maximum input current, number of input circuits, conversion efficiency, and how output limiting is handled. How large the PCS capacity should be relative to module capacity depends on expected generation, output limiting, and design policy. When oversizing is applied, annual energy production may increase, but during periods of high solar irradiance the PCS may limit output. In simulations, you need to check to what extent this limiting occurs and whether it matches the design intent.

The settings for the number of series and the number of parallels are also important. If the number of series is too low, the PCS may not fall sufficiently within its operating voltage range. Conversely, if the number of series is too high, an increase in voltage at low temperatures may exceed the allowable range. Increasing the number of parallels also affects constraints on input current and the number of circuits. When checking how to configure these in the PVSyst manual, it is important not only to see whether warnings appear but to be able to explain why you chose that particular series/parallel configuration.

When configuring modules and PCS, also verify that the values registered in the database match the values in the specification sheets actually being used. Even if model names are similar, outputs and electrical characteristics may differ. In practice, it is desirable to perform the settings while cross-checking with equipment specifications, design drawings, single-line wiring diagrams, and layout drawings. Even when using database values as-is, confirming they do not conflict with the specifications adopted for the project will make explanations in later stages easier.

Additionally, when there are multiple module orientations or multiple PCS configurations within the same power plant, care must be taken in how the system is divided. Combining everything into a single representative condition makes the work simple, but it may not adequately reflect actual generation trends. Conversely, dividing it too finely increases input errors and management burden. It is important to decide, according to the design objectives, which scope should be treated as having the same conditions.

Module and PCS settings are the central part of solar PV design. When reading the PVSyst manual, proceed while checking not only the operating procedures but also electrical consistency, conformity with equipment specifications, and the relationship to the design intent, so you move closer to a simulation that can be explained in practice.

Basic 4: Set loss conditions to reflect actual field conditions

In photovoltaic system design using PVSyst, the settings for loss conditions influence the results. In generation simulations, the energy theoretically obtainable from solar irradiance does not directly become the final generated energy. Depending on the extent to which you account for factors such as temperature losses, soiling, shading, mismatch, wiring losses, PCS conversion losses, equipment downtime, and degradation over time, the way the results appear will change. When checking loss items in the PVSyst manual, it is important to understand the meaning of each item and configure them with an approach that closely reflects actual site conditions.

A common problem with loss conditions is using initial values or values from past projects without justification. Initial values are convenient as a starting point for inputs, but they are not necessarily suitable for every project. For example, in locations with a lot of dust, areas with snowfall, places prone to bird activity, sites with many surrounding trees, or locations affected by sea breezes, the considerations for soiling and maintenance change. The expected soiling losses can also vary depending on the local management regime and cleaning frequency.

Temperature losses are also important. Modules tend to have reduced output as their temperature rises. The way module temperature increases depends on whether the installation is ground-mounted, roof-mounted, close to roof-integrated, and on the quality of ventilation. When checking temperature-related settings in the PVSyst manual, confirm that the assumptions match the installation type and ventilation conditions. In particular, rooftop installations may have limited rear ventilation, and treating them the same as ground-mounted installations can lead to discrepancies with actual conditions.

Wiring losses depend on cable length, current, voltage, conductor size, and circuit configuration. In the early stages of design, approximate values may be used, but as the design approaches the detailed (construction) phase, it is necessary to verify them based on single-line diagrams and wiring plans. Underestimating wiring losses can lead to overestimated power generation, while overestimating them can make design evaluations excessively conservative. What is important is not only the values themselves but also clearly documenting the rationale for adopting those values.

Shading losses require particular attention in practical explanations. Shading can affect not only the annual energy yield but also occur concentrated in specific seasons or times of day. Moreover, depending on the electrical connections, shading on some modules can propagate its effects to an entire string or circuit. When reviewing how shading losses are treated in the PVSyst manual, it is advisable to verify not only simple solar irradiance blocking but also the extent to which the chosen settings can reflect electrical impacts.

Consideration of equipment downtime and availability is also something that is easy to overlook. In actual power plants, inspections, failures, grid-side constraints, communication malfunctions, output curtailment, and other factors mean operations cannot always be conducted under ideal conditions. However, if all of these are uniformly assumed to be large, the simulation results can become overly conservative. Depending on the project's objectives, it is necessary to clarify which losses will be handled within PVSyst and which will be evaluated in separate documentation.

When setting loss conditions, it is important not to rely only on vague judgments like “this is generally the case,” but to decide while referring to site conditions, design drawings, maintenance plans, past similar projects, and so on. The PVSyst manual is useful for understanding each item, but the final settings must be determined based on the specific project’s conditions. Carefully organizing the loss conditions improves the ability to explain the expected power generation.

Basic 5: Do not judge the results screen based solely on power output

When you run a simulation in PVSyst, you can check results such as annual energy production, specific yield, performance ratio, and a breakdown of losses. What you should be careful about is not judging quality solely by the energy production figures. When reading the PVSyst manual, it is also important to understand how to interpret the result screens. Energy production is presented as the outcome of many input conditions, and to validate it you need to examine the intermediate losses, warnings, and monthly trends.

Annual energy production is the most easily understood metric. However, the annual value alone does not allow you to adequately determine which months have higher generation, which losses are dominant, or whether design issues are being masked. For example, even if the annual generation is close to expectations, there may be significant shading losses in certain seasons. Also, if PCS output curtailment occurs more than anticipated, relying solely on the annual value can cause you to overlook opportunities for design improvement.

The performance ratio is also an important verification metric. It is used as an indicator of how effectively a system is generating power under solar irradiance conditions. However, a high performance ratio does not necessarily mean a good design. The apparent value can vary depending on regional solar irradiance conditions, temperature conditions, whether the system is oversized, and the assumptions made for loss settings. When checking the performance ratio, it is necessary to view it together with the energy yield, the breakdown of losses, and the design conditions.

The breakdown of losses is the part that should be given particular emphasis when reviewing results. By checking whether temperature loss, shading loss, PCS conversion loss, or wiring loss is large, you can identify areas for design improvement. If a specific loss appears large, distinguish whether that value is reasonable for site conditions, the result of an input error, or something that is hard to avoid by design.

Monthly results should also be checked. Because solar power generation changes with seasonal variations in irradiance and solar altitude, generation trends differ from month to month. Temperature losses may increase in summer, and the impact of shading can be greater in winter. By checking monthly generation and losses, you can identify problems that are difficult to see from annual values. Monthly checks are especially important for projects affected by surrounding shading, snow accumulation, or orientation conditions.

Do not take warnings or error messages lightly. Even if the simulation has completed and the power output is displayed, there may be points in the input conditions that require attention. If warnings appear regarding voltage range, series count, input current, capacity ratio, data inconsistencies, etc., check what they mean and review the settings as necessary. If you ignore warnings and submit only the results, it will be difficult to explain the design rationale later when asked.

When viewing the results screen, thinking in terms of comparisons is also important. Rather than looking at a single simulation result in isolation, comparing results under different conditions makes design decisions easier. By comparing multiple conditions—such as changing the tilt angle, changing the azimuth, changing module capacity, changing PCS capacity, or implementing shadow countermeasures—you can identify which factors are most likely to affect power generation and losses.

The purpose of consulting the PVSyst manual on how to interpret results is not merely to read the numbers, but to be able to explain them as part of the design. By comprehensively checking the energy production, performance ratio, breakdown of losses, monthly trends, and the presence or absence of warnings, the simulation results become usable in practice.

How to Conduct Checks to Apply the PVSyst Manual in Practice

To make practical use of the PVSyst manual, it is effective to decide on a reading order and a standard checking format in advance. Rather than checking every item from the start each time, having a common checking procedure for each project reduces input errors and oversights. Especially when multiple people are involved in design or verification, it is important to record the input conditions and the verification results so that interpretations do not differ between personnel.

In practice, it is clearer to first organize the project's basic conditions, and then proceed in the order of meteorological data, installation conditions, equipment settings, loss settings, and result verification. This flow may not exactly match the sequence of operations on PVSyst's interface, but it is natural as an order of design decisions. By first solidifying the design objectives and site conditions and then translating them into on-screen inputs, the conditions are less likely to shift midway.

After entering data, always take time to perform a self-check. Verify each item one by one: the entered location, azimuth, tilt, system capacity, module model, PCS configuration, series/parallel counts, loss values, shading conditions, etc. Numeric entries in particular are prone to errors in units, sign errors, and digit-entry errors. Because the direction of the azimuth angle, the input of the tilt angle, the ranges of voltage and current, and cable conditions can significantly affect the results, check them carefully.

Also, when submitting results, it is desirable to provide documentation that explains the input conditions together with the results. If you present only the power output, the recipient cannot judge its validity unless they know the conditions under which those figures were obtained. Organizing the installation location, meteorological data, equipment configuration, loss conditions, shading conditions, main results, and points to note will make internal review and explanations to the client smoother.

When changing conditions, it is important to retain the differences between the before and after states. In solar PV design, module layout, PCS capacity, tilt angle, shading conditions, loss settings, and so on are often adjusted many times. Recording how changes to each condition affected energy output and losses makes it easier to explain why the final proposal was chosen. Conversely, if you do not keep those differences, you may be unable to revert to past proposals and the rationale behind decisions can become unclear.

The PVSyst manual can be used not only to look up unfamiliar operations but also to prevent oversights when verifying design conditions. By confirming the meaning of items in the manual, incorporating them into your company’s verification procedures, and recording the rationale for inputs for each project, simulation work shifts from being dependent on individuals to being a reproducible process.

Summary: A straightforward solar design starts with organizing the conditions

To avoid getting lost in the PVSyst manual, it is important not to try to memorize every detailed function from the outset, but to understand it according to the basic workflow of solar PV design. First, solidify the project conditions and design objectives; next, tailor the meteorological data and installation conditions to the site; then confirm the specifications of the modules and the PCS; bring the loss assumptions closer to actual conditions; and finally review the results not only in terms of energy production but also including the breakdown of losses and monthly trends.

PVSyst has many settings, so when you are unfamiliar with it you tend to focus on the on‑screen operations. However, what truly matters in practice is being able to explain which conditions you entered, why you adopted those values, and how you evaluated the results. The manual is a supporting document for that purpose and does not make design decisions for you.

In solar PV design, small differences in input conditions can affect estimated energy production and loss assessments. That is why it is important to organize site conditions, equipment specifications, layout planning, loss settings, and results verification into a single workflow. By checking conditions each time you work, keeping a record of the basis for inputs, and standardizing how results are interpreted, it becomes easier to maintain quality even when personnel change.

The purpose of mastering the PVSyst manual is not merely to become familiar with its operation. Its true aim is to organize a solar power plant’s design parameters, explain them clearly to stakeholders, and improve the accuracy of design decisions. By leveraging simulations after grasping the fundamentals of photovoltaic design, it becomes easier to make consistent decisions from initial studies through detailed design and client presentations.

To carry out solar designs that more closely reflect actual site conditions, it is important to have a system in place that does not rely solely on simulation results but also verifies on-site survey data, layout drawings, equipment specifications, shading checks, maintenance plans, and so on. To make use of results obtained from PVSyst in design decisions, it is essential to clarify the basis for the input conditions and how to interpret the results, and to connect those to the development of site-appropriate solar power plants.