How to Set the Azimuth in PVSyst | 5 Steps to Interpret Energy Yield Differences

Table of Contents

• Basics to understand before setting the azimuth in PVSyst

• How to think about the impact of azimuth on energy production

• Step 1: Clarify the site's north-south orientation and the design approach

• Step 2: Enter the azimuth in PVSyst's orientation settings

• Step 3: Create multiple cases and compare the differences in azimuth

• Step 4: Interpret monthly changes in energy production and losses

• Step 5: Make the final decision based on site conditions and constructability

• Common mistakes and points to check when setting the azimuth

• How to present azimuths when explaining them in practice

• Summary

Basics to understand before setting the azimuth in PVSyst

When simulating photovoltaic systems in PVSyst, the azimuth setting is an important factor that affects energy production. Solar panels receive different amounts of solar irradiance depending on which direction they face. Even with the same tilt angle, south-facing, southeast-facing, southwest-facing, or east/west-facing arrays will differ in annual energy yield, monthly generation, and hourly generation patterns. Therefore, for practitioners learning how to use PVSyst, the azimuth should be regarded not merely as an input field but as a fundamental parameter for numerically expressing the design intent.

The azimuth angle is the angle that indicates which direction the front of a solar panel faces. In practice, it is often considered in terms of "how many degrees off from true south," evaluating deviations to the east or west with south-facing as the reference. For example, if a roof orientation is shifted slightly west of true south, the layout will receive somewhat more afternoon solar radiation. Conversely, if it is shifted to the east, morning generation tends to be relatively higher. In PVSyst, such azimuth differences can be entered as simulation conditions to check differences in energy production and losses.

One important point to note is that azimuth should not be evaluated on its own. Actual power generation is affected by many factors besides azimuth, including tilt angle, solar irradiance conditions, surrounding shading, the shape of the mounting surface, panel layout, electrical design, and temperature conditions. Even when assessing the difference in energy yield from a slight change in azimuth, you cannot correctly judge the impact of azimuth alone unless you compare cases with other conditions matched as closely as possible. The value of using PVSyst lies in its ability to organize these multiple conditions and quantitatively verify the differences between design proposals.

The optimal azimuth is not always unique. In general, orientations that tend to maximize annual energy production are preferred, but at some sites it may not be possible to install in the ideal orientation due to roof shape, site boundaries, racking layout, access aisles, maintenance access routes, shading effects, the position of power receiving equipment, and so on. Furthermore, for projects that prioritize self-consumption, not only the annual total but also generation in the morning and evening can be important. Therefore, when setting the azimuth in PVSyst, it is important not simply to look for "the orientation that produces the most energy," but to clarify "what to prioritize in this project" before making comparisons.

How to assess the impact of azimuth on power generation

The influence of azimuth on power generation is related to the movement of the sun. Because the sun’s position changes with the seasons and time of day, the amount of solar irradiance a panel receives varies depending on which direction the panel faces. Configurations closer to south-facing tend to receive sunlight more efficiently around midday and thus generally have more stable annual energy production. As the orientation shifts toward the east, morning generation tends to increase; as it shifts toward the west, afternoon generation tends to increase. These differences appear in PVSyst simulation results not only in annual energy production but also in monthly values and hourly trends.

However, the difference in power generation due to azimuth angle also varies depending on the region and the tilt angle. In regions with strong solar radiation, regions where winter solar conditions are severe, or regions where a large share of generation occurs in summer, the same azimuth deviation can produce different apparent results. Also, the effect of azimuth angle can become more noticeable as the tilt angle increases. Conversely, when the tilt is shallow, the differences caused by azimuth may appear relatively small. When comparing with PVSyst, it is necessary not to judge based solely on the azimuth angle, but to evaluate it in combination with the tilt angle.

When interpreting differences in power generation, start by checking the difference in annual energy production. For example, if you shift the azimuth by only a few to a dozen degrees, the difference in annual energy production can be small. However, if it swings significantly in the east-west direction, not only the annual energy production but also the times when generation is concentrated will change. In practice, even if the difference in annual energy production is small, which design is more advantageous can change depending on the times when electricity is used, the conditions for selling power, and the objectives of facility operation. Therefore, when reading PVSyst results, it is important to look not only at the magnitude of energy production but also at differences in generation patterns.

Furthermore, shading effects cannot be separated when comparing azimuths. Even if a direction is theoretically optimal, the presence of buildings, mountains, trees, equipment, or adjacent structures in that direction that cast shadows during certain seasons or times of day will reduce actual power generation. Conversely, an azimuth that looks somewhat unfavorable may be advantageous overall if the layout avoids shading. In PVSyst, reviewing the azimuth settings together with the results of the shading analysis makes it easier to make judgments that closely reflect site conditions.

Step 1: Organize the north–south orientation of the planned site and the design policy

Before setting the azimuth in PVSyst, first clarify the site's north–south direction and the design policy. If you begin entering data with these unclear, you may obtain simulation results but later find it difficult to answer “what reference was used for this azimuth value?” or “does it match the orientation on the drawings?”. In particular, for roof installations, ground-mounted systems, multi-surface installations, and east–west layouts, organizing the azimuth directly affects how easy it is to verify the results.

The first thing to confirm is which “north” is meant by the north shown on drawings and layout plans. In practice, the north on drawings, the north in survey coordinates, and the north verified in the field can be confused. For azimuth settings in photovoltaic systems, you must correctly enter into the simulation the actual direction the panel surface faces. Compare site drawings, layout plans, survey results, topographic data, aerial photographs, and so on, and confirm the facing direction of the panel rows.

Next, decide the purpose for comparing azimuth angles. The cases you should create will differ depending on whether the objective is “maximizing annual energy production,” “evaluating feasible designs that match the roof surface,” or “increasing site utilization with east–west layouts.” If you only want to look at annual energy production, compare multiple angles centered around a south-facing orientation. For projects on existing roofs, use the measured azimuth of the roof surface as the baseline case and examine whether there is room to change it. For ground-mounted installations, also consider the orientation of racking rows, access aisles, the extent of grading, and the direction of shadows.

At this stage, deciding in advance which azimuth candidates to compare will make the work in PVSyst easier to organize. For example, you might create multiple cases with different intents—such as the baseline design, a layout rotated to the east, one rotated to the west, one matched to the roof surface, and one that avoids shading. The important point is not to change numbers arbitrarily, but to give each case a clear purpose. When you later explain the results internally or to the client, being able to say "this case prioritizes annual energy production," "this case prioritizes constructability," or "this case prioritizes avoiding shading" will make the comparison results easier to communicate.

Also, before setting the azimuth angle, confirm the tilt angle and the classification of installation surfaces. If there are multiple roof surfaces or installation surfaces within the same project, representing them all with a single azimuth can deviate from reality. When south, east, and west faces are mixed, each installation surface needs to be treated separately. How to represent multiple surfaces in PVSyst depends on the project conditions, but at a minimum it is important to organize which surface will be treated as which azimuth before entering the data.

Step 2: Enter the azimuth in PVSyst's orientation settings

In PVSyst, when entering an azimuth angle you first open the orientation settings for the design case in question and set the tilt and azimuth angles. The azimuth angle entered here is the basic parameter that indicates which direction the panel surface faces. Because the interface configures tilt and azimuth together, even if you think you only changed the azimuth you need to check that the tilt value has not differed from the previous case. If the purpose of the comparison is to examine differences in azimuth, it is standard to keep tilt, capacity, equipment conditions, and loss conditions the same.

One thing to pay particular attention to when entering data is the sign of angles and the reference direction. In the software’s azimuth notation, deviations toward the east and deviations toward the west may be represented by positive and negative values. If you get this wrong, what you intend to be southeast-facing may end up southwest-facing, or the simulation may run in the opposite direction. After entering numbers in PVSyst, always check the on-screen orientation display and the schematic to ensure it shows the intended direction. Don’t rely solely on the numbers; comparing the visual display with the orientation on the drawings is a basic practical step to prevent configuration errors.

When installing on a roof, it is often the case that you enter the roof surface azimuth as-is. However, a roof edge may not be perfectly straight, or the orientation in the drawings may differ slightly from the on-site orientation. For that reason, recording whether you adopted measured values, drawing values, or estimated values makes later review and explanation easier. In particular, for roofs of existing buildings, relying solely on the site plan can result in a discrepancy with the actual orientation, so on-site verification or corrections using positioning data can be helpful.

For ground-mounted installations the freedom to choose azimuth is relatively high, but they are subject to constraints such as site shape, earthworks, access paths, drainage, neighboring boundaries, and maintainability. Even if PVSyst shows good results for an ideal azimuth, in practice arranging the mounting frames in that orientation may not fit the site, may make access paths difficult to provide, may increase shading effects, or may complicate construction. Therefore, it is important to always work with awareness of whether the entered azimuth can be realized as a practical layout.

When you enter the azimuth, it’s helpful to include clear information in the setting or case names. For example, instead of simply calling them "Case 1" and "Case 2", use names that indicate the content, such as "south-facing reference", "east tilt", "site roof azimuth", or "west tilt". Because PVSyst often handles multiple cases, doing this makes it easy to see which case corresponded to which azimuth when you later view comparison screens or reports, improving the efficiency of verification.

Step 3: Create multiple cases and compare the differences in azimuth

To assess the difference in energy output due to azimuth angle, a single simulation result is not sufficient. By creating a baseline case and several comparison cases that change only the azimuth angle, you can verify how large the differences are. When using PVSyst, a clear workflow is to duplicate an existing case and run simulations after changing only the azimuth value. At that point, if you also change other conditions, you will not be able to determine whether the cause of the energy output difference is the azimuth angle or another factor, so keeping the comparison conditions consistent is important.

When creating comparison cases, first determine the reference azimuth. For ground-mounted installations where orientation is flexible, the reference is often an option close to due south. For roof installations, use the azimuth that matches the actual roof surface as the reference. From there, create options rotated toward the east, rotated toward the west, and options adapted to site constraints. The angular increment depends on the project's objectives, but making it too fine makes it difficult to organize the results. In preliminary studies it is practical to look for trends with larger increments, and in the final analysis to compare more finely within the feasible range.

What matters in comparisons is to look at the differences in simulation results not only in absolute terms but also as percentages. Even if the difference in annual energy production appears small numerically, when the system size is large the impact on the overall project can be non-negligible. Conversely, the difference may be small in percentage terms, and the benefits in constructability or land use may be judged more important. When reviewing PVSyst results, evaluate the differences in energy production, differences in losses, month-by-month variations, and compatibility with operational objectives together.

When the azimuth is changed, note that the timing of peak power generation also shifts. East-facing orientations tend to increase generation in the morning, while west-facing orientations tend to increase generation in the afternoon. Even if the difference in annual generation is small, the generation pattern by time of day can be important depending on demand patterns, contractual conditions, or the purpose of self-consumption. If you can check hourly or monthly output in PVSyst, verifying how generation is distributed over time, not just the aggregate totals, enables decisions that are closer to practical operations.

Also, when creating comparison cases, you must be clear whether you will keep the shadow conditions the same or change the shadow conditions to match actual layout modifications. If you want to see the pure effect of azimuth alone, fix the other conditions and compare. Conversely, when comparing actual design proposals, changing the azimuth can also change panel layout, racking positions, row spacing, and how shadows fall. In that case, it should be treated as a comparison of the overall design proposals rather than a simple azimuth comparison. Not confusing the purpose of the comparison is the key to correctly interpreting the results.

Step 4: Interpreting Changes in Monthly Power Generation and Losses

When comparing azimuths in PVSyst, check not only the annual generation but also the monthly generation. Differences in azimuth affect results differently depending on seasonal solar altitude and irradiation conditions. One azimuth may yield higher generation in summer, while another may show differences in spring or autumn. Even if the annual total shows little difference, a monthly view can reveal that differences are concentrated in specific seasons. In practice, reading monthly generation trends makes it possible to explain equipment operation plans and financial projections more realistically.

When looking at monthly power generation, you should not simply note which month is higher, but check which months show differences as a result of changing the azimuth. For example, when comparing a south-facing baseline case with a west-leaning case, even if the annual difference is small, you may see a tendency for increased generation in the summer afternoons. Conversely, an east-leaning case may show a stronger generation trend in the mornings. This difference is evaluated differently depending on whether the system's purpose is mainly selling power or mainly self-consumption. Examining monthly differences reveals characteristics that are easy to overlook with simple annual values.

Changes in losses are also important. When the azimuth is changed, the way losses due to the angle of incidence and losses due to shading appear may change. In particular, at sites with nearby obstructions, even a small change in azimuth can increase or decrease the impact of morning or evening shading. Checking PVSyst’s loss diagrams and reports and seeing which loss components changed because of the azimuth adjustment makes it easier to explain the causes of generation differences. Even if energy production decreases, it is important to separate whether the reason is the azimuth itself, shading, or the incident conditions.

When interpreting differences in energy production, consider not only the ratios but also the practical implications. Even if changing the azimuth slightly increases annual energy production, that change may not be advantageous if it complicates racking layout, expands the construction scope, or makes maintenance access more difficult. Conversely, even if production falls slightly, if constructability, maintainability, safety, site utilization, and ease of future inspections improve significantly, the design can be reasonable overall. PVSyst results are material for decision-making, not the final decision itself.

Also, when reading reports, verify that the azimuth setting has been correctly applied. When duplicating cases for comparison, mistakes can occur—such as only changing the name and forgetting to change the azimuth, or thinking you changed the azimuth when it was actually applied to a different installation surface. Before reviewing simulation results, check the input conditions page and the settings list to confirm that the azimuth, tilt angle, capacity, and number of surfaces are as expected. Interpreting results should always be done together with confirming the input values.

Step 5: Make the final decision based on site conditions and constructability

After comparing multiple azimuths in PVSyst, the final decision is made taking into account on-site conditions and constructability. The azimuth that produces the most energy in simulation does not necessarily become the actual optimal option. A photovoltaic power installation must be viable in terms of design, construction, and operation and maintenance. Even if you pursue generation output alone, if the design is difficult to construct on site, hard to inspect, obstructs drainage or access routes, or causes significant interference with surrounding equipment, it will be difficult to adopt in practice.

First, what you should check as site conditions are the shape of the site and the roof. For rooftop installations, the orientation of the roof surface is almost fixed, so the freedom to choose the azimuth is limited. In this case, rather than forcing the layout to an ideal azimuth, it is important to correctly evaluate the power generation of each roof surface and to look at the overall power generation by combining multiple surfaces. For ground-mounted installations, site boundaries, land development plans, roads, surrounding buildings, trees, utility poles, existing equipment, drainage direction, and so on influence the selection of azimuth. Cross-check the comparison results in PVSyst with the on-site drawings to confirm whether the layout is feasible.

From the perspective of constructability, confirm the arrangement of the racking, foundation positions, work-flow lines, delivery routes, and maintenance access. Even if a slight change in azimuth increases power generation, if it makes construction more complex and increases rework on site, the overall benefit is small. Especially for large-scale ground-mounted installations, changing the azimuth can affect row layout and the extent of site preparation, and as a result change the overall difficulty of the construction. Even while referring to the numbers in PVSyst, it is necessary to make judgments by iterating with construction drawings and site conditions.

Operations and maintenance should not be overlooked. The orientation and layout of the panels affect the ease of inspection routes, mowing, cleaning, replacement work, and patrols. Even a proposal with slightly higher power generation can increase the long-term operational burden if its layout is difficult to maintain. Since solar power generation facilities are operated for long periods, the azimuth should be determined not only by initial power output but also by inspectability and safety during operation.

For the final decision, organizing the PVSyst comparison results by "energy generation," "losses," "constructability," "site suitability," and "ease of explanation" makes it easier to understand. Compare the option with the highest energy generation, the option that best fits the site constraints, the option that minimizes shading effects, and the option with the best constructability, and select the preferred plan according to the project's priorities. When explaining to internal teams and stakeholders, rather than asserting "this azimuth is the best," it is more practical and persuasive to say, "Under these conditions the difference in energy generation is of this magnitude, and considering constructability and maintainability, this option is reasonable."

Common Mistakes and Checkpoints When Setting Azimuth

One common mistake when setting the azimuth in PVSyst is entering the east/west sign reversed. Southeast- and southwest-facing orientations may not show much difference in annual energy production, but their generation profiles by time of day do differ. In projects that involve explaining self-consumption or demand periods, this input error can lead to significant misunderstandings. After entering the data, always cross-check the displayed orientation and the layout diagram to ensure the direction is as intended.

Another common mistake is confusing the orientation shown on the drawing with the orientation at the site. If the drawing has been rotated for readability, the top of the page is not necessarily north. There can also be discrepancies between the north arrow on the design drawing and the direction confirmed on site. The azimuth to enter into PVSyst should be the actual direction the installation surface faces, not the apparent direction on the drawing. It is important to align the information from the drawing, coordinates, and on-site verification, and to record which value was adopted.

Care must also be taken when handling multiple surfaces. For projects with east and west roof faces, south and north faces, or multiple pitched roofs, combining everything into a single azimuth can fail to accurately represent actual generation trends. If a face has a small installed capacity, it may be treated using a representative value, but when there are multiple primary generation faces, you need to organize and input the azimuth and tilt angle for each face. In particular, for projects that combine east and west faces, the balance of generation between morning and afternoon becomes important, so checking the settings for each face is indispensable.

Also, there are mistakes where you think you have only changed the azimuth angle but other conditions have also been altered. When duplicating cases for comparison, if capacity, equipment configuration, loss conditions, shading settings, weather conditions, etc. do not match, you cannot correctly determine the cause of differences in power generation. Before creating a comparison table, check the input conditions for each case and review whether there are any differences other than the azimuth. In practice, if you omit this check, inconsistencies may be discovered later when preparing explanatory materials, requiring re-simulation.

Finally, when interpreting the results, avoid judging solely by annual energy production. Differences in azimuth appear in monthly and hourly generation and in the loss-item breakdown. Even if the difference in the annual value is small, production can change during time periods that are important for operations. When reading PVSyst results, check the annual energy, monthly energy, the loss diagram, shading effects, and, if necessary, hourly trends, and make a comprehensive assessment of the significance of an azimuth change.

How to Present Azimuths When Explaining Them in Practice

When performing an azimuth comparison in PVSyst, it is important to explain the results clearly to stakeholders. For practitioners, organizing the results into a form that can be used for design decisions and internal communication is more important than simply running the simulation itself. When explaining azimuth choices, do not merely list technical numbers; instead, present in order: "why that orientation was considered," "under what conditions the comparison was made," "how large the difference in energy production is," and "which option is ultimately reasonable."

First, clarify the comparison conditions. Organize the azimuth of the reference case, the azimuth of the comparison case, tilt angle, system capacity, weather conditions, shading conditions, etc., and explain which conditions were held constant and which were changed. If the comparison is intended to examine the effect of azimuth alone, state that explicitly. If comparing actual design proposals, explain that the comparison includes not only azimuth but also layout and shading conditions. If this distinction is ambiguous, interpreting the results will be confusing.

Next, present the difference in annual energy production. However, it is important to explain the significance of the difference, not just the magnitude of production. If the difference in energy production is small, you can explain that "the impact of azimuth differences is limited, and constructability can be prioritized." If the difference is large, you can explain that "changing the azimuth clearly affects energy production, so it is worth reconsidering the layout plan." By phrasing the numbers in terms of design decisions, PVSyst results become easier to use as practical documentation.

Explain monthly generation and differences by time of day as needed. In particular, for projects assuming self-consumption, annual generation alone is insufficient. For facilities with high power demand in the morning, an eastward generation tendency can be meaningful. For facilities with high demand in the afternoon, a westward generation tendency may be valued. By linking differences in azimuth to the demand-side conditions in this way, the explanation becomes a design rationale suited to operational objectives rather than a mere generation comparison.

Also, when shadow effects are included, clarify the relationship between azimuth and shadow losses. For proposals with lower power output, rather than simply attributing it to an unfavorable azimuth, separate the loss factors—morning and evening shadows from surrounding obstacles, seasonal variations in shadow length, inter-row shading caused by layout changes, and so on. This makes it easier to proceed to the next considerations: whether to change the azimuth, to review the layout or row spacing, or to accept the impact of obstacle shadows.

When explaining to stakeholders, it is also important to narrow down and present a single final recommended proposal. Simply lining up the results of multiple cases will leave those reviewing them uncertain about how to decide. Based on the results from PVSyst, indicate an adoption policy that takes into account power generation, constructability, site conditions, and maintenance. For example, summarizing it in a form such as, "Although the reference case produces slightly higher power generation, the difference from the proposal tailored to the actual roof shape is limited, and, considering constructability, we will adopt the orientation that matches the roof surface," makes for an explanation that is easy to understand both technically and practically.

Summary

Setting the azimuth in PVSyst is not simply a matter of entering an angle and running a simulation. It is a series of tasks: confirming the north-south direction of the project site, clarifying the design approach, creating a baseline case and comparison cases, and comprehensively assessing annual generation, monthly generation, losses, shading impacts, and constructability. Azimuth affects energy generation, but the optimal value varies depending on the project's objectives and site conditions. Rather than only pursuing the orientation that maximizes generation, it is important to choose a design that can actually be constructed, is easy to operate over the long term, and is easy to explain to stakeholders.

In practice, when handling azimuth you should first accurately determine the site’s azimuth and ensure the inputs in PVSyst match the drawings and on‑site conditions. Next, create a comparison case that changes only the azimuth and check the difference in energy production. Then verify monthly generation trends, time‑of‑day variations, loss items, and shading effects, and be able to explain why those differences occurred. Finally, by making a comprehensive judgment that includes constructability and maintainability, you can more easily apply PVSyst results to design decisions.

Especially when evaluating azimuth, the accuracy of the input values determines the reliability of the results. If the azimuth on the drawings, the on-site orientation, and the angles of each installation surface remain ambiguous, no matter how carefully you simulate, the results may deviate from reality. In the design of photovoltaic systems, connecting desk-based simulations with on-site information is indispensable. If you can accurately capture the site coordinates, the orientation of the installation surfaces, surrounding obstacles, and terrain undulations, it becomes easier to improve the accuracy of azimuth settings and shading analysis in PVSyst.

Therefore, at the site survey stage, by utilizing LRTK, a smartphone-mounted GNSS high-precision positioning device, and efficiently acquiring location information for candidate installation sites, on-site information necessary to confirm orientation, and records of surrounding structures and topography, it becomes easier to proceed with subsequent design reviews. The work of reading azimuth angles and generation differences in PVSyst is meaningful only when there is an accurate understanding of the site. By retaining high-precision site information and establishing a system to reflect it in simulation conditions, you can achieve solar PV designs that are strong in practical terms — not only in terms of generation forecasts but also regarding constructability and explainability.