6 Items to Review in Installation Angle to Increase Solar Power Generation

When you want to increase solar power generation, reviewing the installation angle is as important as cleaning and measures against shading. The amount of power a solar panel generates depends on the angle at which it receives sunlight. However, increasing the tilt angle does not necessarily always increase output. You need to consider roof pitch, orientation, local insolation conditions, seasonal generation, inter-row shading, wind, snowfall, soiling, and maintainability. This article explains six items to review when reconsidering installation angles to increase solar power generation, aimed at practitioners searching for "how to increase power generation".

Table of Contents

• Basics to know before reviewing the installation angle

• Item 1: Consider monthly generation as well as annual generation

• Item 2: Check constraints of roof pitch and racking angle

• Item 3: Review orientation and installation angle together

• Item 4: Balance inter-row shading with the number of panels that can be installed

• Item 5: Consider effects of soiling, snowfall, and wind in combination with angle

• Item 6: Check your self-consumption hours and the generation curve

• Decisions to avoid when reviewing the installation angle

• Summary

Basics to Know Before Reconsidering the Installation Angle

When reviewing the installation angle to increase the power generation of a solar PV system, the first thing to understand is that the optimal angle is not determined by a single value. The suitable angle varies depending on regional solar irradiation conditions, the building’s roof shape, the panels’ orientation, the area available for installation, shading, wind, snowfall, maintainability, and the facility’s electricity usage patterns. Even if there is an angle generally considered efficient, that angle is not necessarily optimal for every site.

The installation angle of solar panels affects which seasons and how much sunlight they are likely to receive. Increasing the tilt can make them receive more solar radiation in winter, when the sun's altitude is low. On the other hand, increasing the tilt can cause the front and rear rows of panels to cast shadows on each other on flat roofs or ground-mounted installations, requiring wider row spacing. As a result, the number of panels that can be installed may decrease, and the system’s total annual energy generation does not necessarily increase.

Reducing the tilt can sometimes make it easier to place more panels in the same area. When installed along the roof surface, it can also be easier to handle in terms of appearance and ease of installation. However, if the angle is too small, dirt, leaves, and snow may be more likely to remain. Rain may not wash away grime as easily, and long-term power generation can decrease. In other words, you need to consider both short-term installation capacity and long-term maintenance of power generation.

When reviewing the installation angle as a way to increase power generation, it is important not to evaluate the angle in isolation. Adjusting the angle on a poorly oriented surface may have only limited effect. In heavily shaded locations, changing the angle will still leave the impact of shading. If a facility's power demand is skewed toward the morning or the afternoon, a configuration that generates more during the demand hours can be more practically effective than the angle that maximizes annual generation.

Revising the installation angle can increase power generation, but it also affects constructability, safety, and maintainability. Changing the angle can alter racking conditions and thereby change wind effects, loads, fastening methods, and inspection access routes. For existing installations, changing the angle may be difficult. In such cases, it is realistic to consider it at the time of expansion, replacement, or layout changes.

The purpose of reviewing the installation angle is not simply to bring the angle closer to the ideal value. It is to find conditions that, adapted to on-site conditions, increase power generation while being feasible to construct, maintain, and operate stably over the long term.

Item 1: Look at monthly power generation as well as annual power generation

When reassessing the installation angle, the first thing to check is not only the annual power generation but also the monthly power generation. In solar power systems, the way seasonal solar irradiation is received changes depending on the angle. Even if an angle yields a larger total annual generation, it may result in insufficient generation during periods when the facility’s demand is high. Conversely, even if there is little difference in the annual total, improving generation in a particular season can have a significant impact on the effectiveness of the measure.

For example, in winter, because the solar altitude is low, increasing the tilt angle can sometimes increase solar exposure. For facilities with high electricity demand in winter, improving winter power generation becomes important. On the other hand, in summer the solar altitude is high and solar irradiance is greater, so the way generation responds to changes in angle differs from winter. For facilities with high air-conditioning demand in summer, summer generation is more likely to be used for self-consumption, but temperature-related losses due to high temperatures must also be taken into account.

By looking at monthly power generation, you can confirm which seasons are affected by changes in the installation angle. Changing the angle may increase winter generation while slightly reducing summer generation. Conversely, an angle that prioritizes summer generation may make it harder to boost winter generation. If you reconsider the angle as a way to increase generation, it is important to look not only at the annual total but also at the distribution of generation by month.

Additionally, monthly power generation is also affected by shading and snowfall. Increasing the tilt angle can make snow shed more easily, but you need to consider where the snow will fall and available snow accumulation/storage space. At the low solar elevations in winter, shadows from surrounding buildings, rooftop equipment, and trees extend farther. Even if you adjust the angle, if shading is significant, winter power generation may not improve as much as expected.

When comparing installation angles in simulations, examine the annual generation, monthly generation, winter generation, and summer generation separately for each angle. If you overlay the facility’s electricity consumption by month, you can see which angle is most likely to lead to practical benefits. It is important to clarify whether the goal of increasing generation is simply to raise total generation or to boost on-site consumption during months of high demand.

Selecting the tilt angle that maximizes annual energy production is one approach, but it is not sufficient on its own. By checking monthly generation and seeing whether you can increase output during periods that coincide with the facility’s demand, reassessing the installation angle becomes more practical.

Item 2: Check constraints of roof pitch and mounting-frame angle

When reviewing the installation angle, you need to confirm the constraints imposed by the roof pitch and the mounting-frame angle. Even if there is a theoretically optimal angle, it may not be achievable on site. The roof’s shape, structure, waterproofing, loads, wind, constructability, and maintainability all impose limits on the angles that can be adopted.

On roof projects, panels are often installed following the pitch of the existing roof. In that case, the panels' angle is dictated by the roof pitch. Because it is impractical to change the roof's angle itself, improving power generation requires considering which roof surface to use, where to add panels, and which surface's maintenance to prioritize. When installing along an existing roof, the freedom to change the tilt is limited, so decisions must be made in conjunction with orientation, shading, and soiling mitigation.

On a flat roof, it may be possible to set the tilt angle using a mounting system. However, increasing the angle raises wind exposure, so the anchoring and load conditions need to be reviewed carefully. Also, because front and rear rows of panels are more likely to cast shadows, the spacing between rows must be increased. Widening the row spacing can reduce the number of panels that can be installed on the same roof area.

The same applies to ground-mounted installations. Increasing the racking tilt angle can make it easier to receive sunlight in certain seasons, but it affects inter-row shading, wind, snow accumulation, terrain, drainage, and maintenance access. On land with slopes or embankments, the terrain's own incline adds to the tilt. Ignoring the terrain and judging based only on the ideal angle can lead to problems in construction and maintenance.

Also, changing the angle alters the panel height and appearance, the direction of snow shedding, and the maintenance/inspection access routes. On roofs, safety in wind-exposed areas and at roof edges is important. For ground-mounted projects, the locations where snow will fall, the maintenance pathways, and the impact on weed-control work should also be checked. If changing the angle to increase power generation makes maintenance more difficult, it will be harder to sustain generation over the long term.

When reviewing installation angles, it is more important to grasp the range of angles that can be adopted on site than to search for an ideal angle.

After checking roof pitch, racking conditions, structural aspects, waterproofing, wind, and ease of inspection, you need to select, from the feasible angles, a condition that offers a good balance between power output and ease of maintenance.

Item 3: Review Orientation and Tilt Angle Together

When considering the tilt angle, it is important to reassess it together with the panel orientation. If you only change the panel's tilt but the orientation does not match the conditions for power generation, you may not see the expected increase in power output. In solar power generation, the direction the panels face and the angle at which they receive sunlight together determine the amount of electricity produced.

Generally, surfaces oriented toward or near the south tend to achieve higher annual power generation. However, in practice a south-facing orientation is not always the optimal choice. East-facing surfaces tend to generate more in the morning, while west-facing surfaces tend to generate more in the afternoon. If a facility's electricity consumption is high in the morning, east-facing surfaces can contribute to self-consumption; if consumption is high in the afternoon, west-facing surfaces can help. If the goal of increasing generation is to reduce the amount of purchased electricity, it is important to consider not only annual generation but also the overlap between generation hours and demand hours.

Combinations of orientation and tilt angle change the power generation curve. Setting an appropriate tilt on a south-facing array tends to produce generation peaks around midday. Utilizing east- and west-facing surfaces can split the generation peaks into morning and afternoon, which may help reduce midday surplus. Even if a south-facing orientation looks advantageous in terms of total generation, depending on a facility’s demand pattern, designs that include east- and west-facing surfaces can be effective.

In rooftop projects, multiple roof surfaces may face different orientations. Treating south-, east-, west-, and north-leaning surfaces the same makes it difficult to understand the breakdown of energy production. Check each surface's orientation, tilt, energy production, and energy production per unit capacity to determine which surfaces are contributing to generation. Rather than forcibly adding panels to poorly performing surfaces, prioritizing shading countermeasures and soiling mitigation on better-performing surfaces can sometimes lead to greater improvements in energy output.

For flat roofs and ground-mounted projects, you can consider combinations of rack orientation and tilt angle. In this case, consider not only energy generation but also inter-row shading, wind, maintenance access aisles, and connection requirements. Changing the orientation can also alter wiring routes and equipment layouts. It is useful to compare multiple patterns with different orientations and angles to check annual generation, monthly generation, self-consumption, and surplus energy.

Reevaluating the installation angle cannot be done without confirming the orientation. To increase power output, it's important not only to optimize the angle but also to consider which direction to face, when to generate power, and how it will be used within the facility.

Item 4: Consider the balance between inter-row shading and the number of panels that can be installed

Increasing the tilt angle can make panels receive sunlight more easily, but it also makes inter-row shading more likely. This is especially true when multiple rows of panels are arranged on flat roofs or ground-mounted installations, where panels in the front row can cast shadows on those in the rear. If you decide the tilt angle without taking inter-row shading into account, power generation may be lower than expected.

Inter-row shading tends to become particularly problematic in winter when the sun is low in the sky. Even if shading is less of an issue in summer because shadows are short, in winter shadows can extend far enough to fall on panels in the rear rows. Increasing the tilt to improve winter energy production can sometimes increase inter-row shading. Tilt angle and row spacing need to be checked together.

Increasing the spacing between rows can reduce the impact of shading, but it may decrease the number of panels that can be installed on the same roof or land area. In other words, even if you increase the tilt angle to improve per-panel generation efficiency, the reduction in the number of panels installed can mean the system’s annual generation does not increase as much as expected. Conversely, reducing the angle to increase the number of panels can make dirt and snow more likely to remain and can cause seasonal imbalances in generation.

To increase energy output, check the total generation including the number of panels that can be installed, not just the generation efficiency at each tilt angle. When changing the tilt on the same area, compare how many panels can be installed, how much inter-row shading will occur, and how annual and monthly generation will change. It is important to look at both energy generated per unit of capacity and total energy generation.

Additionally, row spacing also affects maintainability. Widening the spacing between rows can make inspections, cleaning, weeding, and checks for snow accumulation easier. Conversely, if rows are placed too close together, maintenance work can become difficult and detection of dirt or defects may be delayed. To sustain power generation over the long term, it is necessary to consider not only generation efficiency but also the role of row spacing as inspection and access routes.

If you evaluate the angle alone without considering the balance between inter-row shading and the number of panels that can be installed, attempts to increase energy output can actually reduce overall efficiency. When reviewing the installation angle, it is important to compare comprehensively the single-panel efficiency, the number of panels that can be installed, inter-row shading, and maintainability.

Item 5: Consider the effects of dirt, snow accumulation, and wind together with the tilt angle

The installation angle affects not only power generation but also the influence of dirt, snow accumulation, and wind. When reviewing the angle to increase power output, do not judge based solely on how solar radiation is received; you need to confirm whether the environment can sustain power generation over the long term.

First, regarding soiling. If the panel angle is small, sand and dust, pollen, bird droppings, fallen leaves, and particulate matter may be more likely to remain on the surface. With a certain degree of tilt, light soiling may be washed away by rain. However, bird droppings and adhered or stubborn dirt may not be removed by rain alone. If you reduce the angle and increase the number of panels installed, you need to check whether dirt will be more likely to remain and whether cleaning will be easy.

Next, the relationship with snowfall. In snowy regions, the tilt angle of the panels affects how easily snow remains on them. If the angle is small, snow is more likely to stay on the panels, which can lengthen the period during which they cannot generate electricity. Increasing the angle can make snow shed more easily, but you need to check where the snow will fall and the available space for snow accumulation. If the fallen snow affects walkways, equipment, or neighboring properties, different problems can arise.

The influence of wind is also important. Increasing the tilt angle enlarges the surface exposed to wind and can increase the load on the racking and fixing arrangements. On roofs, roof edges and high locations can be more susceptible to wind effects. Even for ground-mounted projects, open sites require consideration of strong winds. Changes in angle intended to increase power generation must not compromise safety or constructability.

Dirt, snow accumulation, and wind may not be fully apparent from generation simulations alone. Even if a tilt angle appears to yield high annual generation, if it tends to retain dirt, accumulate snow, or be vulnerable to wind, it may be difficult to maintain generation over the long term. Decisions about changing the tilt angle should be based not only on first-year generation but also on maintainability and safety.

To choose the tilt angle that increases power generation, it is important to look for conditions that are less prone to soiling, make snow impacts easy to manage, do not overstrain the system in wind, and allow easy inspection. By considering not only short-term power output but also preserving long-term power generation, you can make a more practical reassessment of the installation angle.

Item 6: Check self-consumption time periods and the generation curve

When reviewing installation angles, it is important to check not only the annual generation but also the self-consumption time periods and the generation curve. Power generated by solar photovoltaics only leads to self-consumption when it is used on-site at the same time. Even if generation is increased, if the additional output occurs during periods when the facility does not consume power, the improvement in the effectiveness of the installation may be limited.

A power generation curve is a concept that shows how power generation changes over the course of a day. South-facing panels set at an appropriate tilt tend to produce peak generation around midday. East-facing panels tend to generate more in the morning, while west-facing panels tend to generate more in the afternoon. Changing the tilt can affect not only seasonal generation amounts but also the pattern of generation during the day.

If a facility's power demand is high around midday, it's easier to take advantage of the midday generation peak. For facilities whose equipment begins operating in the morning, morning power generation is important. For facilities with high demand in the afternoon, west-facing or otherwise afternoon-tilted configurations that generate more in the afternoon can help with self-consumption. If the aim of increasing generation is to reduce purchased electricity, what's important is not the total amount generated but whether generation can occur during the demand periods.

Changing the installation angle can slightly increase annual generation while not significantly increasing self-consumption. Conversely, even if the increase in annual generation is small, boosting generation during periods of demand can have a large practical effect. When considering how to increase generation, you need to check generation, self-consumption, and surplus electricity separately.

Even when pairing with a battery storage system, checking the power generation curve is important. Confirm how much of the daytime surplus can be stored and how much can be used in the evening and at night. If changing the angle shifts the generation peak, the timing and amount of surplus and how the battery is used may also change.

When selecting an installation angle to increase power generation, check not only the angle that maximizes annual energy output but also whether it can produce a generation curve that matches the facility's demand. Choosing an angle that aligns with the facility's self-consumption hours makes it more likely that improvements in generation will translate into improved implementation outcomes.

Decisions to Avoid When Reassessing Installation Angle

What you should avoid when reassessing the installation angle is simply adopting an angle that is generally considered good. The optimal angle for solar power generation varies depending on region, orientation, roof shape, site conditions, shading, snowfall, wind, and the facility's energy demand.

If you decide the angle without checking on-site conditions, the amount of electricity generated may not increase as much as you expect.

Also, you should avoid judging solely by the maximum annual energy production. Even at the tilt angle that maximizes annual energy production, inter-row shading may increase, the number of panels that can be installed may decrease, and maintainability may worsen. You should also check monthly energy production, self-consumption, surplus electricity, and ease of inspection.

Assuming that increasing the tilt angle will always be better is risky. While it can improve winter power generation, it can also cause greater wind impacts, inter-row shading, snow shedding, racking conditions, and a reduction in installed capacity. Conversely, decreasing the angle can make it easier to increase the number of panels, but it can also make soiling and snow accumulation more likely to persist. It is important to consider both the advantages and disadvantages of the angle.

Be careful about rushing to change the tilt of existing equipment. Existing roofs, mounting frames, and fastening methods have constraints related to structural integrity, waterproofing, and constructability. Changing the tilt requires verification of safety and workability, and it is not something that can be done lightly for the sole reason of increasing power generation. For existing installations, measures such as shading countermeasures, cleaning, equipment inspection, and analysis of generation data can often be more practical ways to improve performance than changing the tilt.

Furthermore, it is also important not to confuse power generation with on-site consumption. Even if changing the angle increases generation, if the facility cannot use it at that time it may only increase surplus. If the purpose of increasing generation is to improve the effectiveness of the installation, you should always check the generation curve and the facility's demand.

Reviewing the installation angle is an effective way to improve power generation, but it is prone to failure if evaluated in isolation. Judging it together with site conditions, construction constraints, maintainability, and demand time periods will yield improvement measures suited to actual operations.

Summary

When reviewing installation angles to increase solar power generation, you need to comprehensively check not only annual energy yield but also monthly yields, roof pitch, racking conditions, orientation, inter-row shading, the number of modules that can be installed, soiling, snow, wind, and self-consumption time periods. Simply changing the angle does not necessarily increase generation; it is important to choose an angle that suits the local site conditions.

In Item 1, we check not only the annual power generation but also the monthly output. It is important to see which seasons’ generation is affected by changes in tilt and whether output can be increased in months when facility demand is high.

In Item 2, we confirm the constraints of roof pitch and racking angle. Decisions should be made based on the angles that can be implemented on site rather than the theoretically optimal angle.

In Item 3, we review orientation and installation angle together. We check not only south-facing surfaces but also east- and west-facing surfaces and their compatibility with the facility’s demand time periods. In Item 4, we look at the balance between inter-row shading and the number of panels that can be installed. Because increasing the tilt angle can increase shading and reduce the number of panels that can be installed, we verify both total generation and generation per unit of capacity. In Item 5, we consider soiling, snow, and wind effects together with the angle. It is important to determine whether the angle will sustain power generation over the long term. In Item 6, we check the facility’s self-consumption periods and the generation curve. Even if generation increases, if it only increases during times when the facility cannot use it, the benefit of installing is limited.

When reviewing the installation angle, you should avoid judging solely by the generally recommended optimal angle, looking only at annual energy production, or assuming that increasing the angle will always be better. To increase power generation, the angle must be evaluated together with local conditions, maintainability, and the time periods of demand.

And to accurately reassess the installation angle, precise on-site information is indispensable. If roof area, rooftop equipment, obstacles, trees, site boundaries, orientation, slope, inspection access routes, and potential connection points can be accurately identified, it becomes easier to assess the effects and constraints of any angle changes.

If you want to accurately record on-site information such as roof and land orientation, slope, obstacles, trees, inspection routes, and candidate connection points, and consider improving power generation by reviewing installation angles, using LRTK, an iPhone-mounted high-precision GNSS positioning device, is effective. If high-precision location information can be obtained on site, it becomes easier to organize roof pitch, causes of shading, installable areas, wiring routes, and maintenance routes, and to proceed seamlessly from angle-by-angle simulation comparisons and pre-construction checks to post-installation performance management. When reviewing installation angles to increase solar power generation, it is important not only to rely on desk-based angle calculations but also to accurately grasp on-site conditions and choose conditions that balance power generation and maintainability.