6 settings in the PVSyst manual for modeling snowy regions

Table of Contents

• Prerequisites to Grasp Before Dealing with Snowy Regions in the PVSyst Manual

• Setting 1 Verify the reproducibility of meteorological data during the snow accumulation period

• Setting 2: Consider the azimuth and tilt angle, including how snow remains.

• Setting 3: Treat the reduction in power generation due to snowfall as monthly losses

• Setting 4: Consider albedo separately for snow-surface reflection and typical ground surface.

• Setting 5: Low-temperature conditions are reflected in string voltage and equipment selection.

• Setting 6: For bifacial power generation, manage reflections from snow on the rear side separately

• Common mistakes in PVSyst settings for snowy regions

• Points to check when reading simulation results

• Summary

Prerequisites Before Dealing with Snowy Regions in the PVSyst Manual

When performing solar PV simulations for snowy regions in the PVSyst manual, the first thing to understand is that snow is not simply a "winter drop in energy production" but a condition that affects multiple configuration parameters. Snow can block incoming solar radiation while also increasing ground reflectivity (albedo). Furthermore, low temperatures raise module voltage, which affects inverter input conditions and string design. Therefore, when modeling a snowy region, it is insufficient to simply increase the loss settings.

In PVSyst, basic conditions such as site, meteorological data, and albedo are set at the Project level, while detailed conditions such as modules, inverters, geometric conditions, shading, and losses are assembled on the Variant side. The official manual likewise describes a structure in which the Project holds the site, meteorological data, and general parameters, and the Variant includes detailed definitions such as modules, inverters, geometric layout, and shading. When examining snowy regions, it is important to be aware of this hierarchy and to delineate which phenomena are handled at the Project level and which are handled at the Variant level.

One point to pay particular attention to is that the behavior of snow itself is not automatically and fully reproduced in PVsyst's meteorological data. PVsyst's official documentation explains that snow is not included in PVsyst's meteorological data, and because it is difficult to predict when snow will shed from the array, it should be considered, as needed, as a partial or complete soiling attenuation for specific months. In other words, in snowy regions the designer must decide which input item(s) to use to represent the effects of snow.

This article outlines six settings that practitioners consulting the PVSyst manual should at minimum check for projects in snowy regions. It applies to typical solar PV projects—roof-mounted and ground-mounted installations, from low- to high-voltage. Specific numerical values vary by project, but if you understand the rationale behind the settings, you can move beyond rough analyses that simply lower winter generation and more easily improve the consistency of design conditions, generation forecasts, and report explanations.

Setting 1: Confirm the reproducibility of meteorological data during the snow season

The first setting to consider when assuming a snowy region is how to select the meteorological data. In PVSyst you set the site and load the meteorological data before proceeding with the simulation. However, for solar power generation in snowy regions, choosing meteorological data based only on annual solar irradiation can lead to incorrect evaluations of winter generation. This is because, in snowy regions, winter solar irradiance, temperature, cloud cover, clear skies after snowfall, and snow surface reflection all combine to affect power generation.

Checking the PVSyst manual shows that when creating a site, data can be imported from multiple meteorological data sources, and that the validity of each data source must be evaluated by the user. Furthermore, TMY data are based on the concept of constructing a representative year from long-term measured data, and their nature differs from synthesized time-series data. In snowy regions, it is essential to verify not only the average solar radiation but also whether the month-by-month winter trends reflect actual conditions.

In practice, you first check the latitude, longitude, and elevation of the simulation site and evaluate how well the meteorological data you are using reflects the amount of snow at the location. Snowfall and solar radiation conditions can vary greatly even within the same prefecture — between coastal and inland areas, and between plains and mountainous regions. On PVSyst the annual irradiance may appear similar, but the monthly irradiance and temperatures from December through March can be inconsistent with local observations. If this discrepancy is left unaddressed, the overall simulation can end up being unrealistic even after adjusting winter loss settings and albedo settings.

In the documentation explaining power generation forecasts, it is important to clarify not only which meteorological data were used but also how snow itself was treated. If the meteorological data represent average irradiance and temperature and do not directly indicate shading of the module surface by snow, that effect should be considered separately as a loss. Conversely, if winter irradiance is already represented conservatively and an additional excessive snow loss is applied, the power generation may be underestimated unnecessarily.

Checking the meteorological data is the foundation of the entire PVSyst configuration for snow-prone regions. If this remains unclear, the basis for subsequent settings — tilt angle, soiling loss, albedo, and temperature conditions — will also be ambiguous. When reading the PVSyst manual, it is important to be aware not only of the on‑screen operations but also of what the input meteorological data represents and what it does not represent.

Setting 2: Consider azimuth and slope angle, including how snow remains

In snowy regions, the next most important factors are the modules’ azimuth and tilt angle. In conventional photovoltaic system design, azimuth and tilt are chosen to maximize annual energy production. However, in areas with heavy snowfall, the tilt angle affects not only energy output but also how long snow remains on the module surface. At low tilt angles, snow is less likely to slide off, potentially prolonging periods of near-zero generation. Conversely, making the tilt too steep can affect summer and annual solar incidence conditions, wind loads, racking costs, aesthetics, and the number of modules that can be installed.

In PVSyst, for fixed installations you set the Plane tilt and Plane azimuth to calculate energy production according to solar altitude and incidence angle. In snowy regions, these settings should not be determined solely by the results of an optimization tool; you need to consider whether the angle promotes snow shedding, whether shed snow will affect lower rows or walkways, and whether it will interfere with snow guards or eave conditions on the roof. In particular for roof-mounted systems, the actual roof pitch is often a fixed constraint, and the ideal values in PVSyst may not match the angles that can actually be installed.

Regarding azimuth, simply orienting closer to due south is not always sufficient. For east–west roofs, multi-surface roofs, terrain shading in mountainous areas, or shading caused by the low solar altitude in winter, the drop in winter generation can be concentrated on specific surfaces. In snowy regions, even south-facing surfaces can experience strong winter shading from upstream obstructions, snow cornices, surrounding trees, or adjacent buildings. When using PVSyst’s 3D scene or near-shade settings, it is important to check how shadows appear at winter solar altitudes and not to confuse snow losses with shading losses.

Also, creating multiple variants with different tilt angles and comparing them is also effective. For example, prepare three options—a standard tilt, a slightly steeper tilt that emphasizes snow shedding, and a low tilt that emphasizes installed capacity—and compare annual generation, winter generation, loss diagrams, and PR. In this case, simply comparing while keeping the monthly loss settings due to snow the same will not capture differences in snow shedding caused by tilt. In practice, it is easier to explain the results if you change the assumed residual snow risk for each tilt angle and organize the rationale for the monthly losses accordingly.

When mastering the PVSyst manual, it is important to understand that the angle you enter on the screen does not simply affect energy production, but is an important parameter that links local snow behavior with design decisions.

Setting 3 Organize decreases in power generation due to snowfall as monthly losses

In PVSyst settings for snowy regions, the aspect most directly related is the treatment of soiling loss. Typically, soiling loss is considered a loss of irradiance caused by dirt, dust, bird droppings, and deposits originating from agricultural or industrial sources. The official PVsyst documentation explains that soiling loss depends on environmental factors such as rainfall conditions, can be defined as monthly values, and is treated as an irradiance loss during simulation.

In the case of snowfall as well, PVsyst's official documentation shows a method for taking it into account by setting partial or complete soiling attenuation for specific months when snow is an issue. This is very important. In other words, the basic concept is not to assume that an independent, detailed "snow" model is always automatically calculated on PVSyst, but to express the solar irradiance that does not reach the module surface because of snow as a monthly loss.

When setting monthly losses in practice, first clarify the snow season for the site. In Japan’s snowy regions, depending on the area you may consider impacts from November through April, or you may focus mainly on December through February. In Hokkaido, Tohoku, Hokuriku, and the mountainous areas of Nagano Prefecture, the snow period, whether the snow is wet or dry, the speed of snowmelt after snowfall, and the number of sunny days vary. Rather than simply assuming “it’s a snowy region, so winter uniformly causes large losses,” it is more natural to assign varying levels of risk by month.

For example, it reflects monthly conditions such as regions where snow is unlikely to settle in December because snowfall is just beginning, regions where snow cover tends to persist in January and February, and regions where solar radiation and rising temperatures in March tend to accelerate snow shedding. For roof-mounted installations, the way snow remains can differ even within the same region depending on roof pitch, roofing material, snow guards, and nearby snow accumulation. For ground-mounted installations, ground clearance, lower-edge clearance, row spacing, snow depth, and snow removal plans have an impact. Because PVSyst’s monthly losses aggregate these site conditions into a single input value, it is essential to document the rationale for the settings.

One point to note is that if you include snow loss in the soiling loss, do not double-count it with the normal soiling loss. In winters with heavy snowfall, entering both a large normal soiling loss and a separate snow loss can lead to a generation estimate that is more pessimistic than the actual situation. Conversely, if you ignore summer dust and agricultural soiling and only include losses for snowy months, that may be insufficient to explain the annual losses. It is practical to separate "normal soiling" and "snow impact" by month in internal notes, and enter the combined value in PVSyst.

When dealing with snowy regions in the PVSyst manual, the soiling loss setting is the item most often asked to be explained in reports. When power producers, financial institutions, contractors, and maintenance companies review the report, they will ask, "why is the loss high for this particular month?" and "is this consistent with past generation performance and snowfall data?" Therefore, monthly losses should not be entered based on intuition; they should be treated as design conditions that take into account local snow depth, snow-removal policy, installation tilt, nearby case studies, and maintenance plans.

Setting 4: Consider albedo separately for snow surface reflection and normal ground surfaces

In snowy regions, snow not only reduces power generation but also acts to increase ground surface reflectance. This is the albedo setting. Albedo is the concept that indicates how much a surface reflects light, and snow surfaces tend to be more reflective than typical soil, grassland, or paved surfaces. In PVSyst you can define the far Albedo in Project settings, and for bifacial generation the idea of defining the albedo beneath the panels on the System window side is described.

What is important here is not to confuse the power reduction caused by snow cover with the increase effect from snow surface reflectance. If the module surface is covered with snow, no matter how high the ground reflectance is, it cannot generate power. Conversely, if the snow on the module has fallen while snow remains on the surrounding ground, the incident irradiance may increase due to reflected light. In other words, snow has two opposing effects: "shading" and "reflection". In PVSyst settings, it is clearer to treat the former mainly as soiling loss and the latter as albedo.

When setting albedo, consider whether to use a single annual value or to allow monthly variations. In regions with little snowfall, a constant value is unlikely to cause major issues, but in snowy regions it is more natural to account for snow surface reflectance only during the winter. However, overestimating snow surface reflectance can unnaturally offset the winter generation reduction caused by snow losses. In particular, for single-sided modules the benefit from ground reflection can be limited, so be careful not to underestimate the risk of power generation outage due to snow.

For ground-mounted installations, snow can remain in front of the array and between rows after snowfall, so they are more likely to be affected by winter albedo. In contrast, for roof-mounted installations the reflective conditions change depending on the color of the roofing material, how snow remains, surrounding buildings, the pitch, and eave conditions. When snow remains on the roof surface, it acts in a complex way: rather than simple reflection, it contributes to shading of the module surface and to local reflections from the surroundings. For this reason, in roof-mounted systems it is often easier to prioritize addressing snow-losses first rather than excessively adjusting albedo.

If you read the PVSyst manual, albedo may appear to be a convenient standalone correction value. However, in snowy regions you should not use it lightly as a setting to increase energy yield; you need to treat it carefully as a parameter representing ground surface conditions. If you raise the albedo for months with snow, also check how much module-surface snow loss occurs in those same months and adjust so that the overall energy yield remains consistent.

Setting 5 Low-temperature conditions should be reflected in string voltage and equipment selection

In snowy regions, low-temperature conditions are also an important setting. The open-circuit voltage of a photovoltaic module increases as temperature decreases. Therefore, in cold regions, if the number of modules connected in series in a string is too large, the inverter's maximum input voltage or absolute voltage limit may be exceeded under low-temperature conditions. In PVSyst settings for snowy regions, you must check not only the energy yield but also whether the electrical design at low temperatures remains on the safe side.

In PVSyst's Project settings, the official manual explains that you can set the site's minimum possible temperature as a design condition and use it to generate warning messages related to the Absolute Voltage limit. However, the same section also explains that the simulation itself may use the temperature from the site's meteorological data. In other words, the minimum temperature setting should be understood as an important condition for string design and warning checks, rather than a value that directly changes the annual energy yield.

In practice, the question is which value to use for the minimum temperature. The minimum temperature included in representative-year meteorological data alone may not sufficiently represent the extreme low temperatures relevant to design. In snow-prone or cold regions, past minimum temperatures, design standards, equipment manufacturers’ conditions, and the site elevation are taken into account, and a conservative value may be adopted. In particular for high-voltage and extra-high-voltage projects, or for projects in mountainous areas and in the inland parts of Hokkaido and Tohoku, neglecting to check voltages under low-temperature conditions can make it necessary to revise the string configuration at a later stage.

Also, low temperatures can have a positive effect on power generation. When module temperature is low, conversion efficiency tends to increase, and on clear days with reflection from the snow surface, momentary high output may occur. On the other hand, if modules are covered by snow they cannot generate power. Therefore, in snowy regions, rather than simplifying the situation to "no generation in winter," it is necessary to consider that high output may occur on clear, cold days after the snow has fallen off. When examining inverter capacity, overloading ratio, clipping, and the DC/AC ratio, these winter-specific conditions must not be overlooked.

In PVSyst, when you configure the module, inverter, number of modules in series, and number of parallel strings, warnings and consistency checks are performed according to the design conditions. In snowy regions, always check not only the MPPT lower limit during high summer temperatures but also the maximum voltage during low winter temperatures. When reading the temperature conditions in the PVSyst manual, it is important to distinguish between the meteorological temperature used for energy yield prediction and the extreme low-temperature conditions used for equipment selection.

Setting 6: Manage the rear-side snow-surface reflection separately for bifacial power generation

In recent years, the adoption of bifacial modules in ground-mounted projects has been increasing. When considering bifacial generation in snowy regions, increased rear-side generation from snow-surface reflection can be expected, but there are also risks such as front-side shading by snow, snow accumulation at the lower edge, rear-side shading from the racking, and insufficient ground clearance. Therefore, even more than with monofacial modules, albedo, ground clearance, row spacing, racking shadow, and mismatch need to be examined carefully.

In the official PVsyst documentation, it is explained that Ground albedo is the albedo of the ground beneath the panels and is separate from the albedo of distant terrain set in the Project, and that it can be set as monthly values to account for snow. This is very important for bifacial PV in snowy regions. If you expect reflection from snow cover, you need to correctly handle the Ground albedo on the bifacial model side as well as the general albedo on the Project side.

However, setting a high snow ground albedo does not necessarily increase energy yield. The light reaching the rear side is influenced not only by ground reflection but also by module height above ground, row spacing, racking geometry, shadows from nearby structures, and the distribution of irradiance on the module rear surface. PVsyst’s bifacial generation documentation also explains that rear-side shadows from structures and mismatch losses due to non-uniform rear irradiance are important factors. In snowy regions, while an increase in ground reflection can be expected, the racking and the snow itself can also affect the rear side, so optimistic settings should be avoided.

Ground clearance in particular is important. If the bottom edge of the module is low, in years with deep snowfall the lower part of the module can become buried in snow, which may obstruct light reaching the front and rear surfaces. Raising the ground clearance makes it easier to reduce snow risk, but it affects racking cost, wind loads, constructability, and maintainability. PVSyst can compare energy yield, but final design decisions need to be evaluated by considering structure, construction, maintenance, and snow-removal plans together.

When dealing with bifacial PV in snowy regions, set the winter ground albedo by month and, at the same time, account for front-side snow shading using soiling loss. Furthermore, verify that structural shading and mismatch losses are reasonable, and avoid emphasizing only the increases due to snow-surface reflection. In reports, it tends to be difficult to explain because snow-induced losses and gains from snow-surface reflection coexist. Therefore, organizing the rationale into "front-side snow shading", "ground snow reflection", "rear-side structural shading", and "electrical conditions at low temperatures" will make it easier to explain to stakeholders.

Common Mistakes in PVSyst Settings for Snowy Regions

One common mistake in PVSyst settings for snowy regions is attributing all the reasons for reduced winter generation to the soiling loss. Indeed, treating snow-induced shading as a monthly soiling loss is practical, but in reality weather data, tilt angle, shading, albedo, low temperatures, and bifacial generation conditions all combine to affect output. If you simply inflate the loss, it becomes hard to explain why that value was reached and difficult to compare results when the design is changed.

Another mistake is setting the albedo too high. Because snow-covered ground is perceived as highly reflective, people tend to set a high winter albedo. However, if module surfaces are covered by snow for extended periods, shading losses will dominate over the benefits of reflected light. Especially for monofacial modules at low tilt and in projects where snow removal is difficult, it is important not to overestimate the improvement in energy production from increased albedo.

Overlooking low-temperature conditions is also a major mistake. If you only look at the power generation simulation results and do not adequately check string voltage warnings and the design temperature, you may encounter inverter input voltage issues in cold regions. When evaluating PVSyst for snow-prone areas, you need to check not only annual energy yield, PR, and the loss diagram but also the voltage conditions and warnings on the system design screen.

Moreover, you should avoid fixing settings without comparing them to actual performance data. If there is an existing power plant nearby, checking its monthly winter generation and shutdown trends can improve the validity of the assumed snow losses. Of course, you cannot make a simple one-to-one comparison because the existing plant may not have the same tilt, racking, or snow-removal conditions, but it at least provides a basis to avoid settings that are extremely optimistic or pessimistic.

Key Points to Check When Reading Simulation Results

After running a PVSyst simulation for a snowy region, always check the monthly results as well as the annual energy production. Because the impact of snow is concentrated in specific months, the appropriateness of the settings cannot be judged from annual values alone. Check the energy production, PR, and loss breakdowns from December through March, and verify that they are consistent with the monthly soiling loss and albedo settings. If winter generation is unusually high, snow losses may be underestimated. Conversely, if winter generation is almost zero, check whether snow losses are set too high or whether the meteorological data itself is overly conservative.

The Loss Diagram is also important. In PVSyst reports, the loss diagram lets you identify which factors are reducing the energy production. In snowy regions, check to what extent soiling loss, IAM, temperature loss, wiring loss, inverter loss, shading loss, etc., are affecting the output. If the effect of snow is included in the soiling loss, you need to verify how much the monthly settings are impacting the annual loss and be able to explain it.

Comparing multiple variants is also effective. By comparing snow loss across three tiers—standard case, conservative case, and optimistic case—you can reveal the sensitivity of generation forecasts. Comparisons should be tailored to project-specific issues, such as changing the tilt angle, altering the height above ground, varying the albedo for bifacial generation, and assuming with or without snow removal. When explaining to financiers or operators, demonstrating sensitivity to snow conditions is more useful for decision-making than presenting a single result.

Finally, the results from PVSyst are merely simulations based on the input conditions and do not fully predict how snow will fall or the status of snow removal. When forecasting power generation in snowy regions, it is important to make assessments that combine the approach of the PVSyst manual with local conditions, construction plans, maintenance plans, and historical performance.

Summary

When modeling snowy regions in the PVSyst manual, there isn't just one setting to check. Meteorological data, azimuth and tilt angles, monthly soiling loss, albedo, low-temperature voltage conditions, and rear-side reflection for bifacial generation all need to be checked comprehensively. In particular, because snow can both cover module surfaces and reduce power output while increasing ground reflectance, it's important to separate loss factors from gain factors.

The most important thing is to manage the settings in PVSyst not as mere data entry but as design assumptions that represent site conditions. When entering monthly snow losses, record the target month, loss rate, justification, snow-removal conditions, and installation angle as a set. When adjusting albedo, verify the period during which snow-surface reflection is expected and its relationship to snow shading of the module surface. When setting low-temperature conditions, confirm not only the energy yield but also the safety of string voltage and inverter input conditions.

Solar power generation in snowy regions involves significant uncertainty in winter output, yet conditions such as clear, cold skies and snow-surface reflections can sometimes be advantageous. For that reason, it is important to read the PVSyst manual and clarify which phenomena are represented by which settings. To improve the accuracy of generation forecasts, you need to judge by linking the official manual’s approach with the actual local snowfall conditions, the design conditions, and the maintenance policy.

In practical work using PVSyst for snowy regions, check the meteorological data, consider the tilt angle and snow shedding, set monthly losses, handle albedo carefully, verify voltage at low temperatures, and for bifacial generation examine the snow-surface reflection on the rear side. By addressing these six points, you can make simulations that not only avoid simply overestimating winter generation declines but are also explainable and easier to compare. When using the PVSyst manual, organizing the phenomena specific to snowy regions before entering numerical values and producing a report in which the input values correspond to the design rationale leads to a more reliable energy-yield assessment.