PVSyst Manual: 7 Criteria for Determining Azimuth and Tilt

Table of Contents

• What you should understand before determining azimuth and tilt in PVSyst

• Criterion 1: Confirm the operational objectives, not just maximize annual power generation.

• Criterion 2: Assess orientation not only as true south but by how well it matches demand time periods

• Criterion 3: Consider the tilt angle separately according to latitude, roof conditions, and installation method

• Criterion 4: Check shade conditions together with orientation and slope

• Criterion 5: For multiple faces or east-west arrangements, separate and organize the conditions for each face.

• Criterion 6: Align simulation conditions with actual construction conditions

• Criterion 7: Preserve a rationale that can be explained in the output report

• Errors in judgment to avoid when using the PVSyst manual

• Concept for connecting azimuth and inclination analysis with field data

• Summary

What to understand before choosing azimuth and tilt in PVSyst

In solar power generation simulations, azimuth and tilt are basic input parameters entered at the outset, yet they are crucial factors that affect final energy yield, shading losses, layout planning, and the explanatory power of reports. Even when designing while consulting the PVSyst manual, general advice like “face south” or “set the tilt near the latitude” is insufficient. Decisions need to take into account site-specific conditions, roof geometry, surrounding obstructions, the times when electricity is used, and construction constraints.

In PVSyst you can set the azimuth and tilt of fixed-tilt surfaces and check how their combinations affect energy yield. The official documentation also explains that fixed-tilt surfaces are defined by tilt angle and azimuth angle, and that a simple optimization function is provided to compare energy yields for each azimuth and tilt. In other words, what you should check in the PVSyst manual is not only the operational steps but also the decision criteria for how to determine input values.

In studies of azimuth and tilt, the theoretically optimal values often do not match the values that can be implemented on site. For example, ground-mounted systems tend to choose a tilt angle that prioritizes annual energy production, whereas roof-mounted installations often follow the roof pitch. For self-consumption systems, not only the peak daytime generation but also the east–west generation balance may be considered to match morning and evening power demand. In snowy regions, snow-shedding characteristics, in high-wind areas the mounting structures and wind loads, and where there are nearby buildings or trees, shading losses cannot be ignored.

This article organizes seven criteria to check when deciding azimuth and tilt in the PVSyst manual, presented in an order usable in practice. It explains perspectives for using simulation results in design decisions — from how beginners commonly get confused about input values, to handling multiple surfaces, ensuring consistency with shading conditions, and how to document rationale that can be explained in reports.

Criterion 1: Confirm the operational objectives, not just maximize annual power generation

The initial criterion for deciding orientation and tilt is what you prioritize for that solar power installation. In many cases the goal is to maximize annual energy generation, but “maximum annual generation” is not the only correct answer for every project. For projects primarily aimed at selling electricity, projects primarily for self-consumption, projects with disaster-preparedness in mind, and projects that need to make the most of limited roof space, the points to be evaluated vary slightly.

When prioritizing annual energy production, one generally looks for an azimuth and tilt that efficiently receive solar irradiation relative to the sun’s annual path. The basic approach is to compare how production changes at multiple angles while checking PVSyst’s azimuth/tilt settings screen and how its optimization is viewed. However, the angle that yields the highest production is not necessarily the easiest to construct. If a minor difference in production would increase racking costs or worsen maintenance access, it may be more rational overall to choose a different angle.

For self-consumption systems, not only the annual power generation but also the times of day when generation occurs are important. In factories and offices, daytime electricity demand is the main component, but for facilities with high loads during morning startup, facilities that operate into the evening, or facilities whose electricity usage patterns differ between weekdays and weekends, it is necessary to check compatibility with the generation curve. Rather than orienting the array due south to maximize midday generation, splitting it east–west to boost morning and evening generation can sometimes reduce surplus power.

Also, if you focus solely on maximizing power generation, you may overlook design risks. Increasing the tilt can be advantageous for winter solar gain, but it affects wind exposure, increases inter-row spacing, raises rack height, and impacts landscape appearance and maintainability. Conversely, reducing the tilt can make it easier to increase installed capacity, but it can lead to more persistent soiling and challenges with snow accumulation and drainage.

When reading the PVSyst manual, it is important to decide what the project is optimizing for—rather than which screen to enter the tilt angle on—before you begin operating the software. If you choose the angle while it is unclear whether to prioritize energy production, economics, self-consumption rate, constructability, or maintainability, you may obtain simulation results but find them difficult to justify as design decisions.

Criterion 2: Evaluate orientation not only by true south but by its alignment with demand time periods

In Japan, solar PV systems commonly use due south as the reference for azimuth. This is because south-facing orientations are the basic direction that tends to receive sunlight more easily throughout the year. However, when evaluating azimuth in PVSyst, it is important not only to check whether a system faces south, but also to verify how deviations toward the east or west affect the power generation curve.

When the orientation is more eastward, generation in the morning tends to increase relatively. When the orientation is more westward, generation in the afternoon tends to increase relatively. Although a south-facing orientation often appears advantageous when comparing only annual generation, if a facility’s power demand is skewed toward the morning or afternoon, slightly adjusting the orientation can provide operational benefits. Especially for self-consumption systems, not only the total amount of generation but also the generation during the hours that overlap with demand is important.

In PVSyst’s fixed-tilt settings, the surface orientation is defined using the tilt angle and the azimuth. The official documentation explains that you can adjust tilt and azimuth on-screen while checking their impact on energy production. Therefore, when deciding the azimuth it is practical not to fix a single value from the outset, but to compare multiple patterns such as south-facing, east-leaning, and west-leaning orientations.

For rooftop installations, because the roof planes of a building are predetermined, it is often not possible to freely choose the orientation. In such cases, you should accurately determine the azimuth of the roof plane and check how much power can be generated at that orientation. If the orientation is ambiguous from the roof plans alone, you need to clarify the basis for the azimuth to be entered by checking on-site surveys, aerial photographs, the north orientation of the drawings, the layout of existing buildings, and so on.

For ground-mounted installations, orientation can be chosen relatively freely, but the site shape, road access, earthworks conditions, row spacing, and surrounding obstacles all have an impact. Even if south-facing is theoretically optimal, aligning with the site's long axis can sometimes increase the number of modules that can be installed or reduce the amount of earthworks required. Because there are sites where changing the orientation by just a few degrees can greatly alter layout efficiency, it is essential to assess PVSyst energy-yield comparisons together with the layout plan rather than relying on the software alone.

When determining azimuth, take care not to confuse the definition of the azimuth angle. Different software and drawings may handle the north reference, south reference, and the sign convention for east/west differently. Check the azimuth definition in the PVSyst manual and correctly convert the orientation read from drawings or survey data before entering it. If the azimuth sign is entered incorrectly, simulation results can change significantly, so always verify in the 3D view and in the report that the orientation is as intended after input.

Criterion 3: Consider the tilt angle separately by latitude, roof conditions, and installation method

The tilt angle is a value that indicates how much a solar panel is inclined relative to the horizontal plane. In general terms, when considering annual energy production, an angle close to the local latitude can serve as a guideline. However, in practice, instead of adopting this guideline as-is, it is necessary to determine the angle by balancing roof conditions, mounting method, snowfall, wind, maintenance, and installed capacity.

For roof-mounted installations, the mounting is often matched to the existing roof pitch. It is possible to assemble the racking at an angle different from the roof, but that affects cost, structural loads, waterproofing, wind loads, aesthetics, and constructability. Therefore, it is important to check the theoretically optimal tilt in PVSyst and compare it with the result when installed at the roof pitch. If the difference in energy production is small, matching the roof pitch can be more reasonable overall.

For ground-mounted installations, it is easy to freely set the tilt angle, but increasing the tilt makes shadows from the front row more likely to extend to the back row. As a result, it may be necessary to widen the spacing between rows, which can reduce the capacity that can be installed on the same site. Conversely, reducing the tilt makes it easier to keep row spacing down, but it can affect winter solar gain and how easily dirt is washed off. In other words, the tilt angle should be considered not only for the efficiency of a single panel but also for the layout efficiency across the entire site.

In snowy regions, the tilt angle affects snow shedding. When the tilt is low, snow tends to remain and the period of power generation downtime may be longer. Conversely, increasing the tilt requires consideration of racking height, wind effects, and the safety of snow discharge locations.

In hot regions, not only the tilt angle itself but also ventilation and how heat escapes from the back of the panels affect power output. Installations mounted flush to the roof and those with ensured ventilation can produce different results even with the same orientation and tilt.

When dealing with tilt angle in the PVSyst manual, it is important to consider not only the angle entered on the input screen but also its interactions with meteorological conditions and loss settings. Changing the tilt angle alters how solar radiation is received, nearby shading, row spacing, soiling, snow accumulation, wind effects, and the assessment of temperature conditions. Rather than optimizing tilt alone, reviewing it together with multiple other parameters produces a simulation that is closer to reality.

Criterion 4: Verify shading conditions together with orientation and tilt

Shade conditions are a criterion that must always be checked when determining orientation and tilt. Even if the theoretical orientation and tilt are ideal, significant shading from surrounding buildings, trees, utility poles, roof structures, or adjacent rows of panels will reduce actual power generation. In particular, for rooftop installations, shadows from parapets, chimneys, air-conditioning equipment, lightning rods, and neighboring buildings tend to have an impact, while for ground-mounted installations nearby woodlands, slopes, and elevation differences on developed land can become problematic.

PVSyst allows you to check the impact of shading using a 3D scene for near shading. The official documentation explains that the orientation of the PV surface defined in the 3D scene must match the orientation defined in Orientation. This is very important in practice, because if the azimuth and tilt input values are misaligned with the panel surface in the 3D scene, the energy production and shading assessment will not be correctly linked.

When checking shading conditions, you need to consider the variation in solar altitude throughout the year. In winter the sun's altitude is low, so shadows from the same obstacle extend much farther. In summer the sun's altitude is high, and even small obstacles on the roof can produce localized shading at certain times of day. In PVSyst's shading analysis, it's important not only to place obstacles but to verify in which seasons and at which times shadows occur, and to reflect that in azimuth and tilt decisions.

Changing the tilt angle also alters the effect of shading. Increasing the tilt can make the panel surface face the sun for longer periods at certain times, but it can also make inter-row shading more likely. Reducing the tilt can help suppress inter-row shading, but it changes the incident light conditions during seasons with low solar altitude. If the orientation is shifted east or west, the timing of shadow occurrence also changes, so a shading assessment based on a south-facing orientation is insufficient.

In PVSyst’s near-shading, a table of shadow factors is created and the impact of shading is evaluated according to the sun position. Therefore, in practice it is more effective not only to check shading after fixing azimuth and tilt but to adjust azimuth and tilt while observing shading conditions. Especially in projects with many obstacles, choosing an angle that reduces shading can result in a higher annual effective energy production than the theoretically optimal angle.

Criterion 5: For multiple surfaces or east–west arrangements, organize the conditions separately for each surface

In roof-mounted installations and on complex sites, not all panels will share the same orientation and tilt. Many projects feature a mix of surfaces — east and west faces, south and west faces, multiple roof pitches, and staggered layouts adapted to the terrain. In such cases, treating the entire system using a single average orientation and tilt makes estimates of energy production and losses coarse.

PVSyst's Orientation-related documentation explains the concept of associating sub-arrays and 3D fields with each orientation. In other words, when dealing with multiple surfaces you need to organize the azimuth and tilt of each surface, the number of modules, the string configuration, and the inverter configuration, and clarify which surface corresponds to which electrical system.

In an east–west layout, the peak generation times differ between the east-facing and west-facing surfaces. East-facing tends to generate in the morning and west-facing in the afternoon, and combined they can produce a generation curve that is smoother compared with a south-facing layout. This can be advantageous for self-consumption systems, but if you look only at annual energy yield the evaluation may be different. When comparing in PVSyst, it is effective to separate and check multiple patterns such as a single south-facing layout, an east–west layout, and a roof-plane layout.

The main concern when dealing with multiple faces is consistency with the electrical design. If panels with different orientations or tilts are mixed on the same MPPT or the same string, differences in irradiance conditions can affect power generation efficiency. Even if you separate faces in PVSyst, you will not achieve consistency between the simulation and the actual design if the real electrical system does not match. Orientation and tilt should be considered not only in the layout but also together with the assignment of strings, inverters, and MPPTs.

Also, when entering multiple surfaces, it is important to organize the names and conditions for each surface. For example, assigning names that remain understandable later—such as east roof, west roof, south roof, low-slope roof, and extension—will make it easier to explain during report checks and design reviews. While operating with the PVSyst manual, rather than simply completing the inputs, ensure the conditions are recorded so that a third party can follow them; this leads to professional-quality work.

Criterion 6: Match simulation conditions with actual construction conditions

The biggest thing to avoid when entering azimuth and tilt is a mismatch between the conditions in PVSyst and the actual construction conditions. If the simulation is calculated for an ideal south-facing 30° tilt but the final design ends up southwest-facing at 10° to match the roof slope, the results cannot be used as a basis for design. Because azimuth and tilt are often provisionally set at an early stage, they must be managed and updated as the design progresses.

To confirm consistency with construction conditions, cross-check the drawings, on-site survey, surveying data, racking drawings, and module layout drawings. For roof installations, check not only the roof plan and elevation drawings but also the actual roof pitch, ridge direction, and locations of obstructions. For ground-mounted installations, check the grading plan, ground slope, reference height of the racking, row orientation, and the relationship with slopes and neighboring property boundaries. On sloped sites, not only the tilt of the panel surface but also the slope of the ground itself can affect the apparent orientation.

PVSyst's documentation presents the approach for checking the consistency between fields defined in the 3D scene and their orientation. When using proximity shading or 3D scenes, it is important to verify that the panel surface orientation, the 3D field(s), and the subarray relationships are not misaligned. This check is not merely to avoid visual errors on the screen, but to ensure that the assumptions behind the simulation results match those of the construction drawings.

Care is required when design changes occur. Although the initial proposal was planned as south-facing, the layout may be altered due to structural reviews, fire access routes, interference with rooftop equipment, or shading effects. If you produce a report using the previous conditions without updating PVSyst’s azimuth and tilt, you will present a power generation estimate that differs from the actual design. This is especially important when the report is used for estimates, contracts, materials for financial institutions, or internal approval documents—confirming consistency with the final drawings is essential.

In practice, it's reassuring to record the date the azimuth and tilt values were determined, the supporting documents, the reference drawing numbers, and the person who verified them. Rather than simply following the PVSyst manual, leaving the rationale for input values as project documentation makes it less likely you'll be confused when revisiting conditions later. Because simulations return results that are faithful to the input assumptions, managing those assumptions is what determines the reliability of the results.

Criterion 7: Preserve evidence that can be explained in the output report

The final criterion for determining azimuth and tilt in PVSyst is whether you can explain them to someone who reads the output report. Conditions that only the simulation engineer understands are inadequate for internal reviews, customer briefings, meetings with installers, and explanations to financial institutions and other stakeholders. Because azimuth and tilt are reflected in the report as basic conditions, you must be able to explain why those values were chosen.

There are four bases for explanation: local conditions, design objectives, comparison results, and constraints. Local conditions are the roof surface orientation, site azimuth, surrounding obstacles, topography, and so on. Design objectives include maximizing annual power generation, improving self-consumption rate, maximizing installed capacity, and prioritizing constructability. Comparison results are the outcomes of comparing multiple orientations and tilts using PVSyst. Constraints include roof pitch, structure, wind load, snow, maintenance access, equipment interference, and so on.

For example, even if 30 degrees due south is theoretically advantageous, in practice the roof pitch may be 10 degrees, and adding mounting racks would increase cost and load, so you can explain that you adopted the roof's 10-degree pitch. Alternatively, although annual power generation is slightly lower than with a single south-facing array, you can explain that arranging panels east–west increased installed capacity and improved alignment with self-consumption time periods. In this way, it is important to verbalize the reasons for the decision, not just the power generation.

The official PVSyst documentation describes screens for checking the correspondence between Orientation management and the 3D scene. When viewing the report, check not only the azimuth and tilt values, but also which surface corresponds to which sub-array, whether the proximity-shading settings are consistent, and whether the conditions for multiple surfaces are properly organized.

To make the conditions explainable in the output report, it is helpful to keep the comparison patterns that were considered during the review. In addition to the adopted option, briefly record the reasons why rejected options were not chosen so you can explain later if asked, "Why did you choose this angle?" Learning how to operate PVSyst from the manual is important, but in practice you must present the results obtained from those operations in a form that can be explained as design decisions.

Judgment Mistakes to Avoid When Using the PVSyst Manual

When setting azimuth and tilt while referring to the PVSyst manual, there are mistakes that beginners often make. The most common is getting the sign of the azimuth wrong. If the east–west direction is entered the wrong way around, the timing of power generation and the shading assessment will change significantly. Always check the panel surface orientation on the screen and confirm it matches the site orientation you expect.

Next, there is the mistake of oversimplifying roof planes and ground slopes. If a roof has multiple planes but you enter them collectively with an average orientation and tilt, predicted energy production and shading can differ from actual conditions. Especially for east- and west-facing surfaces or staggered roofs, it is more accurate to evaluate the conditions separately for each surface. PVSyst provides an approach for handling multiple orientations, so when surfaces differ you should organize them separately.

Also, optimizing only azimuth and tilt while postponing proximity and inter-row shading is risky. Increasing the tilt angle can increase inter-row shading, and changing the azimuth can make the array more prone to building shadows at certain times. In PVSyst’s proximity shading evaluation, consistency between the panel surface in the 3D scene and the Orientation settings is important, so azimuth/tilt and shading conditions are checked within the same review cycle.

Furthermore, there is also the mistake of adopting optimization results as-is. PVSyst’s orientation and tilt comparison feature is useful for understanding generation trends related to angle, but it does not automatically optimize construction costs, structure, maintenance, snow, wind, or array capacity. Because a proposal with slightly higher generation is not necessarily the best for the project as a whole, PVSyst’s results should be used as a basis for design decisions.

Finally, there are omissions in updating input conditions. There are cases where the azimuth and tilt set at the start of design no longer match the final drawings. If there have been changes to the layout, racking, the adopted area of the roof surface, or the number of modules, the PVSyst conditions should also be reviewed. Before submitting the energy yield report, it is important to confirm that the azimuth and tilt, number of modules, array configuration, shading conditions, and loss settings match the latest drawings.

An approach to connecting orientation and tilt analysis with on-site data

To conduct a high-accuracy study in PVSyst, it is important not only to enter angles on the screen but also to correctly reflect on-site data. Azimuth and tilt are largely determined by the actual roof, site, topography, and obstacles, so we utilize not only drawings but also measured information and on-site verification results.

For roof installations, confirm the roof orientation, tilt, obstacle locations, and available surface area. If existing drawings are outdated, they may not match the actual equipment layout. Because items such as HVAC outdoor units, piping, access walkways, parapets, and skylights may have been added later, it is important to cross-check with on-site photos and survey results. Orientation and tilt settings are more reliable when determined based not only on the roof plan but also on information confirmed on site.

For ground-mounted installations, check the site boundaries, grading slopes, slope faces, surrounding trees, buildings, utility poles, roads, and adjacent property conditions. Even if a plan view appears to allow sufficient placement, in practice unusable areas can arise due to elevation differences, drainage, maintenance access routes, and shading. Before comparing orientation and tilt in PVSyst, you need to organize the site conditions to determine which areas can accommodate panels and in which orientations.

When linking on-site data with PVSyst, the way you use 3D scenes is also important. When evaluating proximity shading, the height and position of obstacles and the orientation of the panel surfaces affect the results. PVSyst’s documentation on proximity shading shows a workflow for evaluating shading impacts using shading coefficients based on the sun position. Therefore, it is important not just to place obstacles roughly, but to prioritize and accurately reflect the elements that affect power generation.

When handling site data, it is also necessary to prioritize the accuracy of input values. Measuring everything in detail is ideal, but in practice there are time and cost constraints. Prioritize roof orientation, tilt, major obstructions, inter-row spacing, and module layout—factors that greatly affect power generation—and make a judgement not to over-detail elements with minor impacts. The important thing is to ensure sufficient accuracy for the purpose of the simulation.

Consideration of orientation and tilt cannot be completed by desk-based optimization alone. It is necessary to reflect information collected on site into PVSyst and to feed the results obtained from PVSyst back into the site design in a back-and-forth process. By carrying out this exchange, you can move beyond mere theoretical values toward design conditions that can actually be constructed, explained, and withstand operation.

Summary

When determining azimuth and tilt in the PVSyst manual, simply memorizing the procedure is not enough. What matters is being able to explain why you chose that azimuth and tilt in accordance with the project's objectives. The optimal decision will change depending on whether you aim to maximize annual energy production, prioritize compatibility with self-consumption hours, increase installed capacity, or give precedence to constructability and maintainability.

While using true south as the reference for azimuth, verify how deviations to the east or west affect the power generation time periods. Consider the tilt angle not only as a guideline based on latitude but also in balance with roof pitch, ground-mounted racking, snow, wind, soiling, row spacing, and installed capacity. Because shading conditions cannot be separated from azimuth and tilt, confirm that they are consistent with the 3D scene and nearby shading settings. For multiple surfaces or east–west layouts, organize the conditions for each surface and the corresponding electrical system, and avoid oversimplifying by relying on average values.

Also, it is essential to align the input conditions in PVSyst with the actual construction conditions. If there are design changes, update the orientation and tilt, module layout, array configuration, and shading conditions, and verify that the assumptions in the latest drawings and reports are consistent. Ultimately, leaving a documented basis in the output report that can be explained to a third party is what ensures the reliability of the simulation results.

PVSyst is a powerful tool for comparing how differences in azimuth and tilt affect energy production and for supporting design decisions. However, the quality of the results depends on the quality of the input conditions. When using the PVSyst manual, consider screen operations, site conditions, design objectives, construction constraints, and report explanations together, and determine the azimuth and tilt that can be used in actual solar power generation plans.