Five criteria for considering array spacing in the PVSyst manual

Table of Contents

• The significance of considering array spacing in the PVSyst manual

• Do not determine array spacing based solely on power generation.

• Criterion 1: How much shading around the winter solstice is acceptable

• Criterion 2: Read the required distance from the tilt angle and panel height

• Criterion 3: Use the shading losses on PVSyst for design decisions

• Standard 4: Ensure aisle width, maintenance access routes, and constructability

• Criterion 5: Assess the balance between land-use ratio and power generation

• Basic steps for checking array spacing in PVSyst

• Common mistakes in array spacing settings

• A practical, easy-to-use confirmation workflow

• Summary

The meaning of considering array spacing in the PVSyst manual

Many people who consult the PVSyst manual about array spacing have concerns in solar power plant design such as "how much space should be left between rows," "how much shading loss can be tolerated," and "how should simulation results be interpreted?" Array spacing is not simply the distance that prevents panels from colliding. It is an important design parameter that affects power generation, the occurrence of shading, land use efficiency, maintenance operations, construction costs, site development planning, and racking specifications.

Especially for ground-mounted solar PV systems, if you misunderstand how to space the arrays, winter generation can fall below expectations and shading losses in the morning and evening can increase. On the other hand, if you widen the spacing too much to avoid shadows, the number of panels that can be installed on the same site decreases, reducing system capacity and annual energy production. In other words, array spacing is neither “the wider the better” nor “the tighter the better.” It is a decision factor for determining where to strike the balance, based on site conditions and generation simulations.

PVSyst is a widely used simulation tool for evaluating energy production and performing loss analysis of photovoltaic (PV) systems. When handling array spacing in PVSyst, you need to comprehensively check not only simple dimensional inputs but also the tilt angle, azimuth, topography, number of rows, shading conditions, near-field shading, far-field shading, and loss diagrams. Parts that are difficult to understand from the manual alone should be interpreted in terms of the practical workflow—what each input field actually means and where on the results screens you can look to make a judgment.

In this article, we present five criteria from the PVSyst manual that you should keep in mind when considering array spacing, organized in a form that's easy to use in practical design work. Rather than relying solely on formulas, we explain the order in which to consider them, which setting mistakes to watch out for, and how to reinterpret simulation results.

Do not determine array spacing based solely on power output

When considering array spacing, the first thing that comes to mind is energy yield. If shading between rows is reduced, the solar irradiance incident on the photovoltaic modules increases and losses decrease. Therefore, it is very important to adjust the spacing while checking shading losses in PVSyst. However, trying to maximize energy yield alone can make the design difficult to implement in practice.

For example, if you increase the spacing between rows to almost eliminate shading, the number of arrays that can be placed on the site decreases. Even if the power generation efficiency per panel rises, if the plant’s overall installed capacity is reduced, the annual energy output and project viability can suffer. Conversely, if you pack the rows too closely to maximize land use, shadows from the front rows can fall on the rear rows in winter, increasing simulated shading losses. The impact of inter-row shading cannot be ignored, especially during seasons or times of day when the solar altitude is low.

Also, the spacing between arrays affects how easy maintenance work is. Considering mowing, weed removal, inspection of weed-control sheets, checking mounting-frame bolts, cable inspections, panel cleaning, and replacement work in case of failures, a width that allows people and machinery to pass safely is necessary. If row spacing is reduced solely to prioritize power generation, maintenance vehicles may not be able to enter, increasing operation and maintenance costs.

Furthermore, terrain conditions are also important. On flat land it is easier to design with a uniform row spacing, but on sloped or graded sites the way shadows appear changes depending on the height difference between the front and rear rows. South-facing slopes, north-facing slopes, east–west inclines, level differences, slope faces, and the position of drainage ditches can change shading losses even with the same array spacing. When running simulations in PVSyst, you must also verify how well the site conditions are being reflected.

In other words, array spacing is a design parameter that simultaneously affects energy production, shading losses, installed capacity, land use efficiency, constructability, maintainability, terrain conditions, and cost. When reading the PVSyst manual, it is important not to simply memorize the input method, but to understand it from the perspective of "where in actual design decision-making this input value will have an effect."

Criterion 1: How much shading around the winter solstice is acceptable

The first criterion when considering array spacing is how much shading near the winter solstice can be tolerated. In solar power generation, the solar altitude decreases as winter approaches, and shadows from front-row arrays extend farther toward the rear rows. Therefore, when evaluating inter-row shading, winter conditions rather than summer ones should be emphasized. In particular, on the mornings and afternoons around the winter solstice, shadows tend to be longer and the impact of array spacing becomes more significant.

However, making a single day at the winter solstice completely free of shadows is not necessarily the correct solution. Around the winter solstice the solar altitude is low and the solar irradiance itself is seasonally limited, so if row spacing is increased too much to completely avoid shadows, it can be disadvantageous over the course of the year. What matters is not just whether shadows appear at a particular time on a particular day, but how much those shadows affect annual power generation and economic performance.

In PVSyst, you can assess the impact of inter-row shading on energy production through the proximity shading settings and loss evaluation. What you should look at here is not just whether shading exists. Check what percentage loss the shading causes over the year, whether the losses are biased toward particular months, and whether they are concentrated in specific time periods. If the loss is small and occurs only during winter and does not significantly affect annual energy production, a decision to prioritize land use efficiency may be justified.

On the other hand, if long periods of shading occur in winter—from morning to late morning, or from early afternoon to evening—caution is required. Solar photovoltaic modules can experience a significant drop in output due to partial shading. The way the shading affects performance varies with string configuration and the operation of bypass diodes, but when shadows fall continuously along cell rows, the losses can be larger than what a simple area ratio would suggest.

Therefore, when considering array spacing, first clarify the decision axes: "Should the design completely avoid shading around the winter solstice?", "Is shading during certain time periods acceptable?", or "If annual losses are within a certain range, should land use be prioritized?" If these criteria remain vague, entering values into PVSyst will not allow you to judge whether the results are good or bad when you see them.

In practice, there are approaches that emphasize the period around solar noon on the winter solstice, those that prioritize the hours with the highest generation, and those that judge by the annual loss rate. The decision also depends on whether the project's purpose is selling electricity, self-consumption, or prioritizing generation during peak hours. When learning about array spacing in the PVSyst manual, it is important to first establish the premise of "which time-of-day shadows are acceptable and to what extent."

Criterion 2: Reading the required distance from the tilt angle and panel height

Next, the tilt angle and panel height are important. Because array spacing is determined by whether the shadow of the front-row array reaches the rear-row array, the installation angle and height of the solar modules have a large impact. In general, increasing the tilt angle raises the height at the panels’ rear edge, making the shadows more likely to be longer. Therefore, even on the same site, the larger the tilt angle, the wider the required array spacing tends to be.

For example, when installed at a low tilt angle, the shadows cast by the front row become relatively short. It's easier to keep the row spacing small, making it possible to place more arrays on the site. However, if the tilt angle is reduced too much, annual energy production may decrease depending on the location and orientation, and rain may not wash away soiling as effectively. Conversely, increasing the tilt angle can make it easier to receive winter sunlight, but it lengthens inter-row shadows and also affects wind loads and racking costs.

When considering array spacing in PVSyst, it is important not to determine the tilt angle in isolation. Changing the tilt angle simultaneously affects the way solar radiation is received, inter-row shading, racking height, and the required land area. Therefore, when evaluating array spacing, the tilt angle and row pitch should be compared as a set. Even changing the tilt angle by just 5 degrees can alter shadow patterns and the installable capacity.

One thing to be careful about here is not to confuse "array spacing" with "row pitch." In practice, some people refer to the clearance from the rear edge of the front-row array to the front edge of the back-row array as array spacing, while others treat the distance between the same reference points of the front and back rows as row pitch. If you do not verify which positions the dimensions used in PVSyst's input screens and manuals refer to, the actual layout and the simulation conditions may end up misaligned.

By aligning the panel vertical dimension, tilt angle, minimum racking height, installation height from the ground surface, and the reference points of the front and rear rows, you can verify the shadow length in a way that closely matches reality. Especially for ground-mounted installations, the height from the ground to the bottom edge of the panels and the rear-edge height of the array affect the shadows. It is important to compare the racking manufacturer's standard drawings and layout plans with the model in PVSyst to see whether they match.

Additionally, at sites in snowy regions or where weed control is necessary, ground clearance is sometimes set higher. When ground clearance increases, the point where the shadow starts also rises, changing how shadows reach the rear rows. By reflecting not only the tilt angle but also the overall height conditions of the array, array-spacing analysis in PVSyst becomes closer to real-world practice.

Criterion 3: Use PVSyst's shading losses for design decisions

The third criterion is to use shading losses in PVSyst for design decisions. If array spacing is determined only by the dimensions on the drawings, the arrangement may look neat, yet you can overlook its actual impact on energy yield. In PVSyst, by configuring proximity shading and layout conditions you can check how shadows between arrays are reflected in the simulation results.

When evaluating shading losses, it is important not to judge solely by the annual loss rate. Even if the annual figure looks small, losses can be concentrated in specific months. For projects that place particular emphasis on winter power generation, it is necessary to check monthly losses and the effects by time of day. Conversely, if the impact on the overall year is small and it does not significantly affect project economics, you may consider prioritizing installed capacity and constructability rather than forcibly widening the spacing.

What you should first check in the PVSyst results is where the reduction in energy production due to shading is positioned among the overall losses. The loss diagram displays various losses such as temperature loss, wiring loss, mismatch loss, inverter loss, and so on. Looking only at the shading loss related to array spacing does not lead to overall optimization. If widening the array spacing to reduce shading loss causes the installed capacity to decrease, the final annual energy production may also decline.

Next, confirm under what conditions the shading loss is occurring. You must distinguish whether it is shadowing from the front-row array, shadows from nearby buildings or trees, or shadows caused by the terrain. Even if you adjust array spacing, shadows from distant mountains or surrounding obstacles may not improve. If you change only the spacing without separating the causes of the loss, you will end up spending time on ineffective fixes.

Also, in PVSyst's 3D scene and shading settings, check that the array layout you entered matches the actual layout drawing. If the number of columns, azimuth, tilt angle, number of rows, array dimensions, pitch, or ground height are off, the simulation results will diverge from reality. In particular, when transferring conditions from CAD drawings or layout plans into PVSyst, pay careful attention to coordinate orientation, the north direction, reference points, and unit mix-ups.

When assessing shading losses, comparing multiple cases can also be effective. For example, create cases with slightly varied row spacing, cases with different tilt angles, and cases with different installed capacities, and compare each case's annual energy production, shading loss, PR, and installed capacity. Compared to looking at a single simulation result alone, this makes it easier to see what improves and what worsens when particular conditions are changed.

When reading the PVSyst manual, it is important to be aware not only of how to operate the shading settings but also of how to compare the results. Array spacing is not something you simply enter and finish with; it is an item to reconsider in the design after reviewing the results.

Criterion 4: Ensure aisle widths, maintenance access routes, and constructability

The fourth criterion is aisle width, maintenance access routes, and constructability. Array spacing cannot be determined by power generation simulations alone. On site, tasks such as people walking, transporting materials, using tools, performing inspections, mowing, and replacing failed modules occur. If these are ignored and row spacing is compressed, operation and maintenance after completion will become a significant burden.

At solar power plants, not only the power generation at completion but also the ability to operate stably over the long term is important. If the spacing between rows is too narrow, brush mowers or small maintenance machines will have difficulty getting in. Workers may need to crouch or adopt awkward postures to inspect wiring and mounting racks. In locations that become muddy after rain, on slopes, or near drainage ditches, additional safety precautions are required.

Array spacing is also important during construction. Erection of the mounting structure, pile driving, module delivery, wiring, electrical work, inspections and so on all require working space. Even if panels can be placed in the design, if construction machinery cannot access the site, workers cannot move easily, or a materials storage area cannot be secured, the construction schedule and costs will be affected. Even if a layout shows good energy yield in PVSyst, if it is impractical for on-site construction it cannot be considered the optimal practical solution.

Maintenance access planning must consider not only routine inspections but also emergency response. It is necessary to assess whether failed panels or junction boxes can be accessed, whether inspections can be carried out safely in the event of abnormal heating or wire breaks, and whether access routes for fire services or service vehicles are obstructed. In designs with reduced array spacing, responding to these issues can become difficult.

Also, it may not be necessary to make aisle widths the same for every row. You can design varying widths according to use—for example, main circulation aisles, transverse aisles for maintenance, perimeter aisles, and areas around equipment that require frequent inspection. However, when using a simplified model in PVSyst, the actual aisle layout and the simulation model may not match exactly. In that case, it is important to understand the differences between the model used for energy yield assessment and the layout drawings used for construction and maintenance.

When considering array spacing, consider the total cost including operation and maintenance, not just energy production. Even if energy production increases slightly, if maintenance work becomes more difficult and annual management costs rise, the project as a whole may be disadvantaged. It is important to set a reasonable spacing while reviewing both PVSyst results and on-site operations.

Criterion 5: Evaluate the balance between land use ratio and electricity generation

The fifth criterion is the balance between land utilization rate and power generation. In solar power plants, how much capacity can be installed on a limited site has a major impact on project viability. Widening array spacing tends to reduce shading losses, but it decreases the number of arrays that can be installed. Tightening spacing makes it easier to increase capacity, but it can increase shading losses. Quantitatively assessing this trade-off is a major reason to use PVSyst.

What is important here is to look separately at the energy produced per 1 kW and the total energy production of the power plant. In cases with wider array spacing, the energy produced per 1 kW may improve. However, if installed capacity becomes smaller, the plant’s total annual energy production may decrease. Conversely, in cases with tighter spacing, even if the energy produced per 1 kW drops slightly, the overall energy production may increase due to the higher capacity.

When assessing project viability, not only annual electricity generation but also construction costs, land costs, site development costs, racking costs, maintenance costs, and grid interconnection conditions are relevant. If land is plentiful and site development costs do not change significantly, a design that increases spacing to reduce losses can be advantageous. On the other hand, for projects with limited land, it may be better to secure capacity even if that means accepting some shading losses.

When comparing multiple cases in PVSyst, it is easier to make judgments if you create cases that change only the array spacing. By keeping the tilt angle, azimuth, module, inverter, wiring conditions, and so on the same and changing only the row spacing, you can more clearly see the effect of spacing on energy production and losses. In addition, comparing cases that change the tilt angle or capacity will allow for more practical decision-making.

However, even when tightening spacing to increase land-use efficiency, it is necessary to check the impact on the electrical design. If shading is concentrated on a particular string, it can affect not only energy yield but also output variability and voltage behavior. Even if losses appear small in PVSyst, if the actual string layout and the direction of the shadows are unfavorable, on-site generation reductions can become noticeable. It is important to coordinate layout planning and electrical design and verify them together.

When assessing the balance between land use efficiency and power generation, understand that "maximum capacity," "minimum loss," and "maximum profit" do not necessarily coincide. The results from PVSyst provide material for comparing those differences. Ultimately, power generation, loss rate, capacity, constructability, maintainability, and business viability are laid out to determine the optimal array spacing for each project.

Basic procedure for checking array spacing in PVSyst

When checking array spacing in PVSyst, rather than immediately diving into detailed shading settings, it's less likely to fail if you organize the design conditions before proceeding. First, confirm the installation location, azimuth, tilt angle, module dimensions, racking height, number of rows, row pitch, site boundaries, and surrounding obstacles; if you input these while they are still unclear, you will later be unable to interpret the results.

The first thing to do is create a reference layout plan. For example, enter the tilt angles and array spacing assumed in the planning drawings as they are, and check the shading losses of the current plan. At this stage, it is more important to understand how much loss the current plan has than to aim for perfect optimization.

Next, create comparison cases by changing the array spacing. Make a case with slightly wider spacing, one with slightly tighter spacing, and one with a different tilt angle, and compare annual energy production, shading losses, PR, and monthly results. If you change multiple conditions at the same time, it becomes unclear which factor affected the results. It’s clearer to first change only the array spacing, and then adjust the tilt angle or capacity afterward.

During proximity shading checks, verify that the 3D model and shading settings match the actual layout. Pay particular attention to the north orientation setting, the array orientation, the row arrangement, ground height, and the reference distance between rows. Even if the drawings show the site as south-facing, a misaligned azimuth setting in PVSyst can greatly change how shadows fall.

After that, review the loss diagram and the monthly results. In the loss diagram, check how much of the total is attributable to shading losses. In the monthly results, verify whether losses are concentrated in winter and whether energy production is lower than expected. By looking at monthly values as well as annual values, you can more concretely understand the impact of array spacing.

Finally, feed the PVSyst results back into the site layout drawings and construction plan. Even if the simulation produces favorable results, it cannot be adopted if it won’t fit on the actual site, if access paths cannot be secured, if it conflicts with the site grading plan, or if it hinders the drainage plan. PVSyst is a tool for design decision-making, and the final layout must be determined in conjunction with on-site conditions.

Common mistakes when setting array spacing

One common mistake when evaluating array spacing is misunderstanding what a dimension actually means. For example, you might think you entered the clearance from the rear edge of the front row to the front edge of the rear row, but in PVSyst it was treated as the row pitch. In that case you end up simulating conditions that are wider or narrower than they actually are, causing the shading loss assessment to be inaccurate. You must always confirm what reference each input field is using.

Another common case is changing only the tilt angle without reviewing the array spacing. Increasing the tilt angle raises the rear edge of the panels and lengthens the shadows. Nevertheless, if the row spacing is kept unchanged, winter shadows may increase more than anticipated. Conversely, reducing the tilt angle may allow the row spacing to be tightened while maintaining the same shading conditions.

Peripheral obstacles and inter-row shading can sometimes be confused. When PVSyst shows shading losses, you need to distinguish whether they are due to array spacing or due to trees, buildings, utility poles, fences, or mountain shadows. Increasing the array spacing will not improve shading from surrounding obstacles. If you misidentify the cause of the losses, you may make ineffective corrections.

There are also cases where people only look at the layout that maximizes power generation and fail to check maintainability. Narrowing the spacing between rows can increase capacity, so the simulated annual energy yield may rise. However, if maintenance access is insufficient and inspections or weeding become difficult, problems will arise in long-term operation. Array spacing needs to be evaluated together with simulation results and on-site operations.

Insufficient reflection of the terrain is also a major problem. Even if a site was entered into PVSyst as flat terrain, in reality there may be slopes or steps, and when there is a large height difference between the front and rear rows the shading pattern changes. Especially on reclaimed or sloped sites, ignoring differences in ground elevation can cause the assessment of shading losses to diverge from reality.

Finally, this is also something to avoid: judging based on a single case. PVSyst is most effective when comparing multiple scenarios. Rather than entering only one array spacing and deciding whether it is good or bad based on the percentage of losses, it is important to see how much the energy generation and losses change when the spacing is varied. By comparing, it becomes easier to identify a suitable design compromise.

Easy-to-Use Verification Flow for Practical Work

When evaluating array spacing in practical work, first fix the design conditions. Confirm the installation site, orientation, tilt angle, module dimensions, racking type, minimum ground clearance, planned system capacity, site boundaries, maintenance aisles, and surrounding obstructions, and align the conditions entered into PVSyst with those on the drawings. If these are not aligned, no matter how detailed the simulation, the results will be weak as a basis for decision-making.

Next, we will create a baseline plan. The baseline plan will use the layout that seems most readily adoptable on-site. Rather than aiming for ideal power generation from the start, creating a realistic plan that takes constructability and site conditions into account makes later comparisons easier. We will check the baseline plan’s shading losses, annual energy generation, PR, and monthly results to identify where the issues are.

After that, we will create comparative proposals with different array spacings. For the option that widens the spacing, we will examine how much shading loss is reduced and how much installed capacity decreases. For the option that narrows the spacing, we will check whether the increase in capacity leads to higher annual power generation and whether shading loss remains within acceptable limits. What is important here is to look not only at generation efficiency but also at the plant’s total power output.

Additionally, consider changing the tilt angle. Not only by changing array spacing, but by slightly lowering the tilt angle you can reduce inter-row shading and preserve capacity. Conversely, if you prioritize winter power generation, increasing the tilt angle can be advantageous. In PVSyst, comparing combinations of tilt angle and array spacing allows you to identify more practical options.

Once the comparison options are assembled, we check not only power generation and losses but also constructability, maintainability, site development plans, drainage plans, and consistency with the electrical design. Even if the results in PVSyst look good, when translated into drawings there may be insufficient access routes, interference with drainage ditches, or inadequate clearance to fences. Simulation results must always be mapped back onto the layout drawings for confirmation.

Finally, document the rationale for the adopted proposal. Record why the array spacing was set to that dimension, how much shading loss was allowed, and in what ways it was advantageous compared with other options; doing so makes internal approvals, owner explanations, and decisions during design changes easier. In practice, it is important to retain not only the PVSyst output results but also the compared conditions and the reasons for the decisions.

Considerations for determining array spacing

When judging array spacing, it's important not to seek an overly simple correct answer. In the design of photovoltaic power plants, the optimal spacing varies depending on site conditions, project plans, local solar irradiation, construction methods, and maintenance policies. Even with the same module and the same tilt angle, the decision may differ between Hokkaido and Kyushu, between flat land and slopes, and between projects for selling power and projects for self-consumption.

By referring to the PVSyst manual, you can learn how to configure settings and interpret calculation results. However, the manual is merely an explanation of the software's functions. In practice, what matters is how you use those functions to make decisions. Rather than taking a simplistic view—saying that smaller shading losses are better, that greater energy production is better, or that larger capacity is better—you need to make judgments by combining multiple evaluation criteria.

What's particularly important is linking the timing of shading to its power-generation value. A slight shadow during the low-irradiance periods of morning or evening has a different impact than a broad shadow during periods of high solar irradiance, even if the shadows themselves are the same. When reviewing PVSyst results, check not just for the presence or absence of shading but how much it affects energy production.

Also, array spacing affects future operations. Even if there are no problems immediately after installation, the growth of surrounding trees, changes in the ground, proliferation of weeds, equipment replacement, or changes in maintenance methods can alter the required aisle widths and shading conditions. Allowing margin at the design stage leads to long-term stable operation.

On the other hand, taking excessive margins reduces land-use efficiency. A solar power plant is a facility that maximizes generation value within a limited site and investment. If you widen the spacing more than necessary, shading losses may decrease but the project's profitability can suffer. Therefore, array spacing is an item that balances the "safety side" and the "revenue side".

Comparing cases in PVSyst is useful for judging this balance. Designers can verify the numerical differences among multiple proposals and make decisions in light of site conditions. The purpose of reading the PVSyst manual is not just to learn screen operations, but to acquire the ability to properly carry out such comparative evaluations.

Summary

In the PVSyst manual, when considering array spacing, simply entering the distance from row to row is not sufficient. Array spacing must be determined comprehensively based on five criteria: shading around the winter solstice, tilt angle and panel height, shading losses in PVSyst, aisle width and maintenance access, and the balance between land use efficiency and energy production.

The first thing to determine is how much shadow during which times of day you are willing to accept. The required spacing will vary depending on whether you want to avoid shadows near the winter solstice entirely or are willing to tolerate them if annual losses are small. Next, look at the tilt angle and panel height. A larger tilt angle makes shadows extend more easily, so the same spacing may result in greater losses.

In PVSyst, you check shading losses, monthly results, and loss diagrams to assess how much array spacing affects energy production. However, you should not decide based solely on simulation results; you must also verify consistency with maintenance access aisles, constructability, site development conditions, drainage planning, and electrical design.

If you increase the array spacing, shading losses tend to decrease, but the installed capacity may be reduced. If you tighten the spacing, it is easier to secure capacity, but the impact of shadows may increase. Which is correct depends on each project. The important thing is to compare multiple cases and make a decision while considering energy production, loss rate, capacity, maintainability, constructability, and commercial viability.

To make the PVSyst manual useful in practice, you need more than just memorizing how to enter inputs—you need the perspective of feeding results back into design decisions. Array spacing is a fundamental condition that determines a solar power plant's performance and operability. By evaluating it against five criteria, you can create layout plans that are evidence-based rather than based on mere intuition or custom.