7 Basic Rules When Entering Site Information in PVSyst

Table of Contents

• Why the accuracy of site information input in PVSyst becomes important

• Basic Rule 1: Clarify the purpose of the input and the project's assumptions first

• Basic Rule 2: Do not be vague about the installation site's location information

• Basic Rule 3: Do not separate your understanding of terrain and elevation from meteorological conditions

• Basic Rule 4: Do not create contradictions with orientation, tilt, and surrounding conditions

• Basic Rule 5: Do not mix provisional conditions with confirmed conditions

• Basic Rule 6: In comparison cases, make common conditions and differences explicit

• Basic Rule 7: After inputting, perform a reverse check from the calculation results

• Thinking to connect PVSyst site information input to practical accuracy

Why the accuracy of site information input in PVSyst becomes important

For practitioners running generation simulations with PVSyst, entering site information is not just an initial setting. Rather, it is a crucial step that establishes the foundation for the entire calculation—covering later-entered equipment configuration, loss assumptions, and approaches to orientation and tilt. If this step is left vague, no matter how carefully you set up the system conditions later, the reliability of the final results will remain unstable.

In practice, attention tends to focus on visually apparent items such as capacity, module layout, and loss settings. On the other hand, site information, once entered, tends to remain fixed as an assumption and therefore is less likely to be revisited. In reality, however, even a slight discrepancy in the installation site's location, sense of terrain, elevation, or understanding of surrounding conditions can change the choice of meteorological data, the monthly generation profile, and the evaluation of comparison options. That is why site information input should be handled carefully from the start.

Also, when using PVSyst professionally, the important thing is not just being able to run calculations but being able to explain why a number turned out as it did. Whether for internal reviews, design comparisons, preliminary commercial judgments, or explanations to clients, clarity of assumptions is required. If site information is poorly organized, the numerical results may exist but the explanation of underlying assumptions will be weak. In practice, the rationale behind the numbers is more important than how large the numbers are.

Furthermore, site information often becomes the starting point for revisions as a project progresses. A location condition that was provisionally set in the initial stage often becomes more concrete after site visits or drawing reviews. Each such update may require reexamining the entire simulation. For that reason, from the first input stage it is important to be aware of which assumptions are provisional and which are confirmed. Below are seven basic rules to pay particular attention to when entering site information in PVSyst.

Basic Rule 1: Clarify the purpose of the input and the project's assumptions first

The first thing to confirm when entering site information in PVSyst is the purpose of the simulation. Whether it is a rough estimate for comparing candidate sites, a plausibility check for a single option, or a preliminary organization of assumptions ahead of detailed study will change the required accuracy and handling of site information. If you start entering data while the purpose is ambiguous, you may waste time entering unnecessary detail or, conversely, be too coarse and struggle to explain the results later.

In practice, multiple purposes often coexist within the same project. It is not uncommon for someone inside the company to want a rough estimate first while the design lead wants to see layout direction. In such cases it is important to organize in advance how far the current input is intended to cover. For example, in the candidate selection stage it makes sense to proceed using a representative point, while in the detailed comparison stage you need a setup closer to the actual site. Clarifying the purpose at the outset makes it easier to determine the depth of site information input.

Also, if you enter site information without organizing the project's assumptions, it becomes unclear what to revise later. If you do not distinguish whether the location is provisionally set, whether elevation sense is near-final, or whether understanding of surrounding conditions is only approximate, you will be unsure where to look when a result feels off. The key to PVSyst site information input is not the act of entry itself but creating a state that is easy to review.

A practical measure is to briefly state the project's purpose before inputting. Simply being able to say whether the input is for candidate comparison, rough explanation, or layout planning reduces confusion. Additionally, consciously separating provisional assumptions from confirmed assumptions makes it easier to reorganize later when conditions change. The basic principle of site information input is not only to enter accurate values but also to clarify what those assumptions are intended for.

Basic Rule 2: Do not be vague about the installation site's location information

Next, it is important not to be vague about the installation site's location information. In PVSyst you set the site point as the entry to site information, but if that point recognition is ambiguous, subsequent meteorological data selection and interpretation of generation output will become unstable. In practice, you may use a representative point near a candidate site, but even in that case you need to be clear in your own mind which point you are treating as the project's site.

The problem with vague location information is not merely concern about map-level errors. In reality, how you pick the point affects meteorological assumptions, sense of orientation, understanding of terrain, and priorities for site visits. For example, within the same region, moving a short distance can change impressions of openness, elevation sense, or whether a site is inland or coastal. In PVSyst, those differences subtly influence how you interpret results.

A common tendency for practitioners is to reference the location data of nearby previous projects and treat the current project's point as roughly the same. While efficient in initial studies, this approach makes it easy for assumption differences to creep in when you compare options. If you want to evaluate design differences but the point conditions differ as well, the meaning of the numbers becomes unclear. Therefore, it is important to eliminate ambiguity about location information from the start.

As a countermeasure, make sure you can explain which point you used as the input reference. Whether it is the planned site's center, a representative location of an area to be developed, or a convenience representative point for a rough estimate—if you can articulate the reason, subsequent review and comparison become easier. In PVSyst site information input, the clarity of why a location was adopted is as important as the precision of the location itself.

Basic Rule 3: Do not separate your understanding of terrain and elevation from meteorological conditions

When entering site information, it is important not to treat your understanding of terrain and elevation in isolation but to consider them as connected assumptions with meteorological conditions. In practice the workflow often goes: set location information, choose meteorological data, then refine equipment conditions. If you proceed without a sense of terrain and elevation, you cannot fully judge the validity of meteorological assumptions. Although PVSyst displays site information and meteorological data as separate items, in reality they are deeply linked.

For example, differences in elevation and surrounding terrain affect not only the impression of the location but also how you interpret temperature conditions and seasonal trends. You do not need to grasp everything precisely at the initial stage, but you should at least have a general sense of the site's terrain environment. Whether you treat the land as flat or consider it to include undulation, whether the surroundings are open or enclosed—all these change how you interpret meteorological data and orientation conditions later.

If you ignore this rule, you are likely to judge meteorological data by numbers alone. In practice, even if meteorological data look favorable, unless they are tied to an understanding of terrain and elevation, the consistency with installation conditions and loss settings will be weak. In other words, terrain and elevation are not just reference items for site information but are materials for deciding how to use meteorological conditions. When using PVSyst you may be tempted to consider each input field separately, but in real projects conditions are interconnected.

As a countermeasure, once you decide on the location, succinctly verbalize the site's terrain and elevation sense. If you organize whether it is flat, has level differences, or features characteristic surrounding terrain, it becomes easier to reconcile meteorological data and orientation assumptions. To avoid mistakes in PVSyst site information input, adopt a mindset of entering numbers while understanding the kind of place the point represents.

Basic Rule 4: Do not create contradictions with orientation, tilt, and surrounding conditions

Entering site information correctly for the point alone is not sufficient. What matters is not creating contradictions with the orientation, tilt, and surrounding conditions that you will set later. PVSyst separates site information, installation conditions, and loss conditions into different fields, but in practice they are a single integrated set. If the way you think about site information does not align with the installation policy you adopt later, the simulation may produce results but will be difficult to explain.

A frequent oversight is assuming that premise organization is complete once site information entry is finished. In reality, if orientation or tilt does not match actual site conditions, or if your understanding of surrounding conditions differs from the site information, you will sense discrepancies in later simulations. For example, if you want to assume an ideal orientation but the actual site does not allow it, you need to revisit how you treat site information. It is important to recognize that site information does not stand alone.

Contradictions with surrounding conditions also affect shadowing and layout thinking. If you lightly assume the surroundings when entering site information, you may later be forced to artificially correct for shade impacts or equipment placement, resulting in a mismatched set of simulation premises. As you progress through PVSyst inputs, attention tends to shift to adjusting individual conditions, but you must always check whether the initial site information aligns with later design conditions.

To address this rule, after entering site information briefly confirm what orientation, tilt, and surrounding conditions you are assuming under that site premise. Even if it is not a detailed design, knowing the general direction makes it easier to spot contradictions early. When handling site information in PVSyst, do not aim merely to finish the input; create an entry that connects with subsequent conditions.

Basic Rule 5: Do not mix provisional conditions with confirmed conditions

A very common issue in practice is mixing provisional conditions and confirmed conditions with equal weight. Site information input is often done at an early stage of the project, so not everything is confirmed. Location may be rough, elevation sense approximate, and surrounding conditions speculative. The problem is failing to recognize that state and later treating provisional assumptions as if they were confirmed.

PVSyst produces neat results, so even provisional assumptions can make the numbers look convincing. However, if you have not organized where provisional assumptions remain, you will not know which results to revise when conditions change later. Using provisional assumptions at the candidate comparison or rough estimate stage is normal. What matters is being clear about what those provisional assumptions are and how close they are to being confirmed.

For example, if you can organize that the representative installation point is provisional, the understanding of surrounding terrain is approximate, and orientation assumptions may vary, you will read results with appropriate caution. Conversely, moving forward to reports or internal presentations without that organization allows numbers to take on a life of their own. Failures in PVSyst site information input are more often due to poor management of provisional assumptions than to input mistakes per se.

As a countermeasure, distinguish provisional assumptions and confirmed assumptions when entering site information. You do not need to manage everything separately, but at least clearly mark items likely to strongly affect the current results as provisional or near-confirmed. Doing so speeds up future revisions and makes it easier to explain assumption differences when creating comparison cases. Using provisional assumptions is not the problem; treating provisional assumptions as confirmed is.

Basic Rule 6: In comparison cases, make common conditions and differences explicit

When using PVSyst in professional contexts, you frequently compare multiple options, not just a single case. In such situations, a key consideration when entering site information is to make clear which conditions are common and which are different. If you increase options without clarifying what you are comparing, it becomes unclear whether result differences are due to installation conditions or differences in site information. The more options you create, the more important this organization becomes.

In practice, comparisons may vary orientation only, change layout only, or compare entirely different candidate sites. Ideally, conditions unrelated to the evaluation point should be kept consistent, but in reality site information can gradually drift as you add options. Then multiple reasons for generation differences accumulate, and it becomes unclear which differences to evaluate. Because PVSyst produces numbers, this mixing is particularly hard to spot.

To prevent this issue, clarify before starting comparisons which conditions will be common and which will be variables. For design comparisons within the same site, it is better to keep site information and meteorological assumptions common; for candidate site comparisons, organize site information using consistent adoption criteria. In short, the important point in comparison cases is not only the correctness of each option but also keeping the differences readable.

Also, following this rule greatly simplifies creating reports and explanatory materials. If common and differing conditions are organized, you can briefly explain what differs in each option and why results changed. If not, documents require extra caveats and reviews and corrections take longer. When entering site information in PVSyst, organize it not only as a premise for a single case but as an assumption that supports comparative operation.

Basic Rule 7: After inputting, perform a reverse check from the calculation results

The final rule is: do not treat site information entry as finished once input is complete. In PVSyst, once you enter assumptions and see results, it is easy to be reassured by the numbers. What is truly important is to use the results to reverse-check the validity of the assumptions. Because site information is entered at the start, it is less likely to be questioned and more likely to retain blind spots. Therefore, you need the perspective of reviewing assumptions through the results.

In practice, people sometimes accept annual generation figures if there is no major discomfort. However, if monthly trends look unnatural, if differences between options do not match expectations, or if losses appear inconsistent, you should return not only to equipment conditions and loss settings but also to the site information itself. The way you picked the location point, your sense of the terrain, and alignment with orientation and surrounding conditions may be too loose.

As a countermeasure for this rule, always include a perspective of returning to assumptions when reviewing results. Check annual values, monthly trends, comparative differences, and the appearance of losses in a consistent order, and if anything feels off, develop a habit of returning to the site information input. PVSyst makes it easy to review assumptions from the results, and performing this round trip stabilizes simulation quality.

Having this reverse-checking perspective also facilitates team reviews. If another team member sees a discrepancy in the results, they can raise site information as a candidate for review as well as equipment conditions. To avoid failure in PVSyst site information input, you need not only initial caution but also the flexibility to question assumptions after seeing results. Input accuracy and ease of revision are equally important in practice.

Thinking to connect PVSyst site information input to practical accuracy

What ties together the seven basic rules above is not treating site information as mere initial settings. By including clarifying the purpose of input, making location information explicit, connecting terrain and elevation to meteorological conditions, ensuring consistency with installation conditions, distinguishing provisional and confirmed assumptions, organizing common and differing conditions for comparisons, and reverse-checking from results, PVSyst site information input moves closer to assumptions usable in practice. Treat site information not just as conditions for calculating generation but as the starting point for design decisions.

For practitioners the priority is not producing the most flattering numbers. The important thing is being able to explain why those assumptions were chosen and to perform inputs that withstand later revisions and comparisons. If site information is poorly organized, equipment comparisons, loss assessments, and report preparation all become unstable. Conversely, if the approach to site information is well organized, PVSyst results are easier to read and easier to explain internally and externally.

If you truly want to improve the accuracy of site information input, do not confine yourself to desk-based entry. Accurate understanding of the installation point, site orientation, surrounding terrain, layout constraints, and potential shading is weakened when field information is vague. Site information does not exist solely within the software screen; its accuracy is determined together with field understanding. In other words, input accuracy is deeply linked to the accuracy of on-site comprehension.

In that sense, when you want to make on-site position confirmation and coordinate acquisition more reliable, it is also effective to utilize iPhone-mounted GNSS high-precision positioning devices such as LRTK. If you can better organize the location information and site conditions gathered on site, it becomes easier to improve the accuracy of the site information you enter in PVSyst. Creating a workflow that refines desk-based simulation accuracy with PVSyst and supports field understanding with LRTK turns site information input from a mere task into a field-rooted design decision. Carefully entering site information not only refines generation forecasts but also enhances the practical capability that connects the desk and the field.

cm精度 -> cm level accuracy (half-inch accuracy)