What is PVSyst? A summary to understand the concept of power generation losses

PVSyst is simulation software used to estimate annual or monthly energy production of photovoltaic power systems by combining factors such as irradiance, photovoltaic modules, mounting conditions, orientation, tilt, shading, temperature, wiring, and conversion efficiencies. Rather than simply calculating generation by “multiplying panel capacity by irradiance,” it is characterized by its ability to organize the various unavoidable production losses that occur in actual power plants in a step-by-step manner.

Many practitioners who search "What is PVSyst" are typically at the stage of beginning to be involved in solar power system design, commercial feasibility assessments, technical reviews, or checking power generation forecast reports, and are likely bewildered by the large number of loss items that appear on the screens and in reports. Generation losses involve many technical terms, and similar-sounding words are often listed together, so at first it’s hard to know where to look. However, once you organize your thinking, PVSyst’s results can be read as practical documentation for confirming "where, and to what extent, the power generation is being reduced."

Table of Contents

• PVSyst is a simulation environment for visualizing power generation losses

• Basic workflow to understand before analyzing generation losses

• How to think about losses related to solar irradiance

• How to think about losses due to shading

• How to think about losses due to temperature

• How to think about losses due to module performance and variability

• How to think about losses occurring in wiring and electrical systems

• How to think about losses related to inverter conversion

• How to think about losses due to soiling, aging, and operating conditions

• Points to watch when reviewing PVSyst results

• How to interpret generation losses to guide design improvements

• Summary

PVSyst is a simulation environment for visualizing power generation losses

PVSyst is a specialized simulation environment for predicting the energy production of photovoltaic (PV) systems. In practice, it is used during power plant planning, design studies, preparation of documentation for financing and investment decisions, and verification of the performance of existing installations. The information entered includes site meteorological data, PV module specifications, inverter specifications, tilt angle, azimuth, row spacing, shading conditions, wiring conditions, loss rates, and so on. By combining these inputs, it estimates how much DC energy will be produced and, ultimately, how much AC energy will be output.

What is important in understanding PVSyst is to look not only at the final energy output value but also at the intermediate steps that lead to that value. Solar power generation does not mean that sunlight from the sun is directly converted into electricity. First, there is the irradiance reaching the installation surface; part of that is received by the module surface and then converted into DC power by the solar cells. After that, it passes through wiring and equipment to the inverter, where it is converted into AC power and treated as the plant's output. At every stage of this flow, small losses occur.

The term "generation loss" is often perceived simply as something "bad." However, in practice generation losses must be assumed to occur. Even in locations with no shading at all, output reduction from temperature rise takes place. Even when selecting high-performance equipment, losses from wiring resistance and conversion efficiency will not be zero. If equipment is operated over a long period, soiling and aging must also be taken into account. In other words, generation loss is not an exceptional problem that lowers the quality of a power plant, but a real condition that should always be included in power generation forecasts.

The role of PVSyst is to break down these losses one by one and clarify how they affect energy production. Looking only at the annual energy production figure, it is difficult to judge whether a plant’s design is truly appropriate or where there is room for improvement. By contrast, if losses are checked at each stage—irradiation, shading, temperature, equipment, wiring, conversion, and operation—the weaknesses in the design and the looseness of the assumptions become much easier to identify.

Basic steps to grasp before understanding power generation losses

To understand generation losses, it is important to follow the flow of energy conversion in photovoltaic (PV) power generation step by step. The first thing to consider is how much solar irradiance reaches the location of the power plant. This varies greatly depending on local climatic conditions. Even with the same installed capacity, annual energy generation differs between regions with high and low solar irradiance. Furthermore, rather than using the irradiance on a horizontal plane as is, consider how much irradiance actually strikes the tilted surface where the modules are installed.

Next, we consider how much of the irradiance reaching the module surface is converted into electricity. Photovoltaic modules have a nominal power rating, but this is a value measured under fixed standard conditions. In real power plants, irradiance intensity, cell temperature, wind, soiling, shading, angle of incidence, and so on are constantly changing. Therefore, the output listed in catalogs is not reproduced on site as-is. PVSyst calculates behavior that is close to reality according to the input conditions and organizes the results as generation losses.

Furthermore, the DC power produced by the modules passes through strings, junction boxes, DC cables, inverters, and so on. During this process, losses occur due to wiring resistance, mismatches caused by combinations of voltage and current, and losses from equipment conversion efficiency. Before being finally output on the AC side, the amount of electrical energy gradually decreases across multiple stages. In PVSyst reports, this flow is organized as a losses diagram, allowing you to trace the reduction from solar irradiance to the final energy output.

What you should be careful about here is that focusing too much on individual generation losses can make it easy to lose sight of the overall picture. For example, a loss rate for a particular item may look small but can be non-negligible because it occurs throughout the year. Conversely, a loss that appears large only in a specific season or time of day may have a limited impact on annual energy production. When reading PVSyst results, you need to look at both the meaning of each loss item and the magnitude of its impact on annual energy production.

Understanding generation losses is not only necessary for judging the quality of a design. It is also important when explaining a power generation forecast report to third parties. If you cannot explain why the projected generation is what it is, under what assumptions it was calculated, and which losses are significant, the numbers will be taken out of context. Practitioners using PVSyst are expected not only to know how to operate the software but also to be able to interpret generation losses.

Approach to Losses Related to Solar Radiation

Irradiance-related losses are an important factor that affect the starting point of generation forecasts. The energy output of a photovoltaic system fundamentally depends on the irradiance reaching the module surface. Therefore, if the choice of meteorological data or the conditions for converting horizontal-plane irradiance to tilted-plane irradiance change, the final energy yield will also change. In PVSyst, the irradiance received by the module surface is calculated based on the site’s meteorological data.

When considering losses related to solar irradiance, the first important question is "which solar irradiance is being used as the reference?" Solar irradiance reaching a horizontal plane, irradiance incident on an inclined surface, and irradiance effectively received at the module surface differ from each other. Tilting the module to face south changes the irradiance received depending on the season and time of day. Arranging modules east–west changes the power generation profile in the morning and evening. A low tilt angle can be advantageous for summer generation, while a high angle can be advantageous in winter.

Also, losses caused by the angle of incidence are important. When sunlight strikes the module surface head-on it is received efficiently, but when it arrives at an oblique angle, reflections and the like reduce the usable light. In the morning and evening and during winter the sun’s altitude tends to be lower, so the impact of the incidence angle becomes larger. PVSyst accounts for these incidence-angle effects, allowing you to identify losses that cannot be determined from simple irradiance alone.

One aspect of solar radiation losses that is easily overlooked is the representativeness of the meteorological data. Even when using data from locations close to the planned power plant site, actual conditions can differ due to surrounding terrain, elevation, distance from the coast, and the tendency for localized cloud formation. In particular, in mountainous areas, coastal regions, snowy areas, and places prone to fog, relying solely on general data can lead to large discrepancies with actual operation. To trust PVSyst's calculation results, it is necessary to confirm not only the source of the solar radiation data but also whether it matches the actual conditions at the site.

Methods to improve solar irradiance losses include reviewing orientation and tilt angle, adjusting row layout, and considering layouts that are less prone to shading. However, the optimal orientation and angle are not determined by energy yield alone. They must be balanced with site shape, site preparation conditions, constructability of the mounting system, maintenance access, wind loads, drainage, land-use efficiency, and other factors. Therefore, PVSyst results should not be used as a tool to determine the optimal solution based solely on energy yield, but as decision-making information to select a reasonable design option by comparing multiple conditions.

Approach to Losses Due to Shading

Shading losses are very apparent in solar PV systems, but they are an item that requires care to handle accurately. When part of a module is shaded by surrounding buildings, trees, mountains, utility poles, fences, or inter-row shading between racking, the generation from that shaded portion decreases.

Shading does not simply reduce output in proportion to the shaded area; it also affects the electrical connections inside the module and the string configuration. For this reason, shading can impact power generation more than it appears.

In PVSyst, by setting shading conditions you can simulate the effects of shading by time of day and season. This is especially important for ground-mounted power plants, where the relationship between row spacing and tilt angle is critical. Narrower row spacing allows more modules to be placed on the same site, but front-row shading is more likely to affect rear rows during winter and in the mornings and evenings. Wider row spacing reduces shading but may result in lower installed capacity. In short, shading losses are an indispensable factor when considering the balance between site utilization and power generation efficiency.

On building roofs and complex sites, shading from nearby obstructions is also important. Chimneys, roof towers, railings, adjacent buildings, and trees can cast elongated shadows depending on the time of day. Even if a shadow falls on only some modules, it can affect the current of the entire string. Especially on roofs that combine multiple orientations and slopes, it is necessary to consider shading impacts together with the electrical configuration.

When interpreting shading losses, it is important not to judge them solely by the annual loss rate. Shading that appears small on an annual basis can be concentrated in specific seasons or times of day. For example, even if shading is large in winter mornings and evenings, its impact on annual energy production is limited if solar irradiance is low during those times. Conversely, if shading occurs around midday when irradiance is high, the effect on generation is greater. When reviewing PVSyst results, you need to consider when the shading occurs and how much generation opportunity exists during those periods.

To reduce shading losses, reviewing the layout, adjusting row spacing, ensuring sufficient distance from obstacles, and optimizing string configuration are effective. However, attempting to completely eliminate shading can significantly reduce installed capacity or affect construction costs and maintainability. In practice, rather than making shading losses zero, it is important to keep them within an acceptable range and balance system capacity, constructability, maintainability, and power generation.

Approach to Losses Due to Temperature

Losses due to temperature are an unavoidable factor when considering the power output of solar photovoltaic systems. Photovoltaic modules generate more electricity the more they are exposed to sunlight, but at the same time their cell temperature rises. Generally, as cell temperature increases, module output decreases. Therefore, during sunny summers, while solar irradiance is high and energy production tends to increase, the output reduction caused by elevated temperatures also tends to be larger. If you do not understand this relationship, you may wonder, "Why isn’t it producing as much as expected despite the high sunlight?"

In PVSyst, cell temperature is estimated based on air temperature, wind speed, mounting configuration, and the module’s rear-side ventilation conditions, and the output reduction due to temperature is calculated. The way modules cool differs between ground-mounted systems with good airflow and installations located close to a roof. If rear-side ventilation is poor, heat tends to accumulate and temperature-related losses can increase. Therefore, temperature losses are influenced not only by meteorological conditions but also by the racking structure and the installation environment.

When interpreting temperature loss, it's easier to understand if you pay attention not only to annual figures but also to seasonal trends. In winter, temperature loss tends to be smaller because ambient temperatures are low, but in regions with low solar irradiance overall power generation may still be limited. In summer, even with high solar irradiance, output can be reduced because cell temperatures rise. In spring and autumn, the balance between air temperature and solar irradiance is often favorable, which can make generation efficiency appear higher. When reading the monthly variation in power generation, it's important to look at solar irradiance and temperature loss together.

Methods to reduce temperature loss include installation methods that ensure ventilation, layouts that prevent excessive heat buildup, and consideration of appropriate mounting-structure heights. However, changing mounting-structure conditions to substantially reduce temperature loss can affect wind loads, constructability, maintainability, aesthetics, and site constraints. Therefore, while temperature loss is an item that can be improved, it needs to be considered realistically within site conditions and design constraints.

Temperature loss is also useful when assessing abnormalities at a power plant. If measured power generation is lower than predicted, you should check the temperature and solar irradiance conditions for the period in question before simply assuming equipment failure. In years with prolonged heat waves, power generation efficiency can decline due to temperature loss even when solar irradiance is sufficient. When evaluating actual performance against PVSyst results, it is important to understand the differences between the meteorological conditions used in the simulation and the actual meteorological conditions.

How to Think About Losses from Module Performance and Variability

Losses associated with photovoltaic modules are factors that directly affect the basic performance of power generation systems. Modules have a nominal output, but in practice there are manufacturing variations and differences in measurement conditions. Furthermore, even modules of the same model do not all have exactly the same electrical characteristics. In solar power generation systems that connect multiple modules in series or parallel, these variations can lead to power generation losses.

A typical example is mismatch loss. For modules connected in series, the way current flows needs to be consistent. If some modules have lower output, the current of the entire string is affected, and the overall energy production can decrease. This can occur not only from shading but also from module-to-module variations, uneven soiling, temperature differences, and differences in the rate of degradation. In PVSyst, such variations are set as a defined loss and reflected in the energy yield predictions.

When considering losses related to module performance, the difference between standard conditions and actual operating conditions is also important. A module’s nominal output is a value measured under fixed irradiance and temperature conditions, but site conditions are constantly changing. Actual energy production deviates from the nominal value due to behavior under low irradiance, temperature characteristics, and the effects of angle of incidence. In PVSyst, generation behavior is calculated based on module characteristics, so the accuracy of the module information entered affects the results.

Long-term aging effects cannot be ignored. Solar PV modules are generally treated on the assumption that their output gradually declines as years of operation progress. Changes that occur from the first year and the gradual degradation from long-term operation need to be considered separately. In business viability assessments, because it is common to project not only the first year's power generation but also the long-term power generation trend, setting the degradation rate is important. However, if the degradation assumption is overly optimistic, future power generation may be overestimated, and if it is overly conservative, the business viability may be underestimated.

When reading module-related losses, it's important not to dismiss them just because the numbers are small. A power plant connects many modules and operates over a long period. Therefore, even small differences in each module can have a non-negligible impact overall. To verify whether the loss values set in PVSyst are reasonable, you need to consider the design conditions, procurement conditions, quality control, installation accuracy, and maintenance plan together.

Considerations for Losses Occurring in Wiring and Electrical Systems

Losses that occur in wiring and electrical systems arise during the process of transporting the DC power generated by the module to the inverter, and further when outputting to the AC side. Typical examples are voltage drops and heating caused by cable resistance. When current flows through wiring, because wiring has resistance, some of the energy is lost as heat. These losses vary depending on the cable length, thickness, material, the magnitude of the current, and the circuit configuration.

In PVSyst, you set the wiring losses for the DC and AC sides, and these are reflected in the power generation forecast. On the DC side, the distance from the modules to the inverter, the string configuration, the location of junction boxes, and the cable routing affect losses. The larger the power plant, the more likely wiring distances will become longer, making loss management important. Even for rooftop installations, inverter placement and cable routing can alter losses.

Wiring losses are an item that can be controlled to some extent during the design stage. Making the cable thicker reduces resistance and can potentially lower losses. However, increasing cable size also affects workability and material quantities. By optimizing inverter placement you can shorten wiring distances, but you must also consider factors such as maintainability, installation space, thermal environment, noise, and inspection access routes. In other words, wiring losses need to be considered not only with power generation but together with construction planning and maintenance management planning.

Electrical system losses also include losses related to connection points, protective devices, transformer equipment, and measuring instruments. Poor connections or variability in construction quality can lead to greater-than-expected losses and heat generation. Even items that are often treated as standard conditions in PVSyst simulations can be significantly affected by construction quality in the actual field. Therefore, to achieve the loss values set in simulations on site, design drawings, construction management, inspection, and maintenance checks are important.

When checking wiring losses, you must not forget safety considerations in addition to the impact on power generation. Excessive voltage drops or heating affect the reliability and maintainability of the equipment. If PVSyst’s results show large wiring losses, you should consider that this may indicate not only a reduction in energy production but also potential need to revise circuit design and equipment layout.

Considerations on Losses in Inverter Conversion

The inverter is a device that converts the direct current power generated by photovoltaic modules into alternating current power that can be used by the grid or loads. Losses always occur during this conversion process. Although inverters have a high level of conversion efficiency, it is not constant under all operating conditions. Efficiency varies with input voltage, input power, temperature, load factor, and so on. In PVSyst, conversion losses are calculated based on inverter characteristics.

What matters for inverters is not only conversion losses. If the input power exceeds the inverter’s allowable range, the output may be limited. This tends to occur when peak DC power exceeds the inverter’s AC output limit, and in design it relates to the concept of oversizing. Oversizing makes it easier to use the inverter effectively under low or intermediate solar irradiance, while during periods of strong irradiance some output may be curtailed.

This output limitation may at first glance appear to be a loss, but it is not necessarily a bad design. As a result of balancing annual energy production, plant capacity, equipment configuration, grid conditions, and business viability, some designs accept a certain output limitation. The important thing is to check in PVSyst how much inverter-related loss is occurring and judge whether that aligns with the design intent. If it is unexpectedly large, you should review the inverter capacity, string configuration, azimuth dispersion, input voltage range, and so on.

Also, inverters have a startup voltage and an operating range. During times of weak solar irradiance, such as mornings, evenings, or cloudy conditions, sufficient input conditions may not be obtained, causing efficiency to drop or creating periods when the inverter may not be able to operate. While the impact may seem small when viewed on an annual basis, it accumulates and affects energy generation. The consistency between the inverter's input conditions and the string configuration is particularly important for systems with multiple orientations or those affected by shading.

When evaluating inverter conversion losses, it is important not to simply compare efficiency figures, but to check whether they match the operating range of the entire installation. Even high-efficiency equipment may fail to deliver the expected performance if the input voltage or load factor is not appropriate. By using PVSyst, you can verify not the performance of individual equipment, but whether the combination for the whole power plant is appropriate.

Approach to losses from soiling, aging, and operating conditions

Losses due to soiling are an important consideration from a viewpoint close to real-world power plant operation. When dust, pollen, bird droppings, fallen leaves, sand, salt, volcanic ash, and other deposits accumulate on module surfaces, sunlight has more difficulty reaching the cells and power generation decreases. Rain can naturally wash them away in some cases, but the extent to which soiling remains varies depending on the region, installation angle, and surrounding environment. On low-tilt installations, deposits may not wash off easily, and the types of soiling differ in agricultural areas, near factories, coastal regions, and along roads with heavy traffic.

In PVSyst, soiling losses are sometimes set as a fixed assumption. The appropriateness of this value varies with the plant’s location and maintenance plan. If cleaning is frequent and the environment makes it difficult for dirt to accumulate, losses can be kept low; however, in sites where cleaning is difficult or soiling is heavy, a more conservative assumption is necessary. Soiling loss is not merely a number in a simulation but is closely linked to operational practices.

Age-related losses are also important. Because power generation equipment is operated for long periods, you need to consider not only the first year’s energy production but also the production after several years. Generation performance gradually changes due to module output degradation, equipment deterioration, changes in the condition of connections, accumulation of soiling, and changes in the surrounding environment. Even when checking the initial design’s generation in PVSyst, it is common to separately account for aging effects in long-term generation forecasts.

Losses due to operational conditions include output curtailment, shutdowns, maintenance inspections, equipment failures, and grid-side constraints. PVSyst’s standard energy production forecast is a technical estimate based on the configured conditions and does not automatically reflect all operational stoppages or unforeseen troubles. Therefore, in feasibility assessments and operational planning, it is necessary to consider—alongside the simulation results—maintenance and inspection plans, spare parts arrangements, monitoring systems, and outage risks.

Losses from soiling, aging, and operational conditions are often underestimated at the design stage, but they can be major factors causing deviations from actual power generation performance. Even if power generation forecasts are precise, insufficient on-site management will prevent achieving the expected power generation. To make practical use of PVSyst results, it is important to link the loss settings in the simulation with the inspections, cleaning, and monitoring actually carried out during operation.

Points to Note When Reviewing PVSyst Results

When reviewing PVSyst results, it is important not to focus solely on the final annual energy production. Annual energy production is an easy-to-understand metric, but you cannot judge its validity without examining the assumptions from which that number was derived. The same annual energy production can mean different things depending on whether the solar irradiance conditions are set conservatively or the loss conditions are set optimistically. In practice, you must always check the result figures together with the underlying assumptions.

Particular attention should be paid to duplication or omission of loss items. For example, even if shading effects are modeled in detail, adding an overly conservative loss in another item can lead to the same effect being counted twice. Conversely, if soiling or downtime risks are not considered at all, the estimated energy output may be more optimistic than reality. PVSyst is a useful calculation environment, but if the input conditions are not appropriate, the output results will not be appropriate either.

Monthly power generation is also important. Even if the annual figures appear fine, examining monthly data can reveal an unnatural drop in a particular season. By checking monthly trends—winter shading, temperature-related losses in summer, reduced solar irradiance during the rainy season, and decreased generation in snowy regions—you can more easily understand the characteristics of the power plant. When comparing actual performance, looking at month-by-month or seasonal data as well as annual totals makes it easier to analyze causes.

When reading a loss diagram, it is important to follow the meaning of each stage in sequence. Starting from solar irradiance and following the flow through tilted-surface irradiance, shading, incidence angle, module conversion, temperature, mismatch, wiring, inverter conversion, and alternating-current output will show where the largest reductions occur. If you skip intermediate items and look only at the final value, you will miss clues for design improvements. Conversely, if you read the loss diagram carefully, you will see what to consider to increase power generation.

Also, the results from PVSyst are not the "correct answer" but predictions based on the assumptions you set. Actual power generation varies due to year-to-year weather differences, installation conditions, operational conditions, individual equipment differences, and changes in the surrounding environment. Therefore, when using simulation results it is important to understand their nature as predictions and not to treat them overly definitively. In practice, you should compare multiple scenarios, check sensitivities, and make decisions that account for risks.

How to View Power Generation Losses to Inform Design Improvements

The purpose of checking generation losses in PVSyst is not simply to read the report. In practice, it is important to examine the breakdown of generation losses and improve design and operation. For example, if shading losses are large, there may be room to review row spacing, layout, distance to obstructions, and string configuration. If temperature losses are large, check ventilation conditions and the mounting configuration. If wiring losses are large, review cable length, cable gauge, and equipment placement.

When considering improvements, it is important not to try to maximize power generation alone. If you widen row spacing to increase power generation, installed capacity may decrease. If you increase cable size to reduce wiring losses, it will affect constructability and material constraints. If you change the layout to avoid shadows, maintenance access routes and land-use efficiency will change. The optimal design is not the one with minimum generation loss, but a design that balances power generation, constructability, safety, maintainability, and commercial viability.

To leverage PVSyst for design improvement, comparing multiple options is effective. Even on the same site, changing azimuth, tilt, row spacing, system capacity, inverter capacity, or string configuration alters how losses occur. In one option shading losses may be small but system capacity may be reduced, while in another option shading losses may be somewhat larger yet annual energy production may be higher. Conducting such comparisons makes it easier to make design decisions that cannot be determined from a single result alone.

Accurate understanding of on-site conditions is also indispensable for improving generation losses. If the site conditions in the simulation differ from reality, you cannot correctly assess the effects of shadows, orientation, tilt, elevation, and surrounding obstacles. If on-site surveying, terrain verification, obstacle checks, and the identification of existing structures’ positions are insufficient, no matter how finely you configure PVSyst, the results may not match the actual situation. The accuracy of power generation simulations is supported not only by software operations but also by the accuracy of on-site information.

Even during the operation phase, PVSyst’s loss analysis is useful. If actual electricity generation is lower than predicted, it provides clues to isolate which loss factors may be responsible. Checking whether irradiance was lower than expected, temperature conditions were harsher, shading or soiling increased, or there were equipment outages makes it easier to develop countermeasures. By linking design-phase simulations with operational performance management, the value of PVSyst is further enhanced.

Summary

PVSyst is not only a tool for predicting the energy production of photovoltaic (PV) power systems, but also a practical simulation environment for clarifying the concept of generation losses. Starting from solar irradiance, you can step through the process by which generated energy becomes the final AC output, including shading, angle of incidence, temperature, module characteristics, mismatch, wiring, inverter conversion, soiling, ageing, and operational conditions. By understanding generation losses, you can explain not just the raw production figures but also the assumptions and design conditions from which those figures were derived.

For practitioners searching "What is PVSyst?", what matters is not memorizing the user interface screens or report items. First, you need to understand that losses always occur in solar power generation, and that losses not only reveal a plant’s weaknesses but also provide clues for design decisions and operational improvements. If shading losses are large, review the layout and row spacing; if temperature losses are large, check ventilation conditions; if wiring losses are large, consider equipment placement and cable design. By interpreting losses one by one like this, you can use the simulation results to inform practical decision-making.

On the other hand, PVSyst results are highly dependent on the input conditions. If meteorological data, site conditions, orientation, tilt, surrounding obstacles, equipment specifications, wiring conditions, or maintenance assumptions differ from reality, the resulting estimated energy production will also diverge from actual performance. In particular, the accuracy of on-site information regarding shading, terrain, and nearby structures is crucial. By carefully obtaining not only desk-based settings but also on-site location and height information and identifying obstacles, the reliability of the energy production simulation is improved.

In designing solar power systems and evaluating energy production, it is important to consider simulations and on-site measurements together rather than separately. If you can accurately capture a site's location, elevation, equipment layout, and surrounding environment, the assumptions used in PVSyst will be closer to reality. If you want to streamline on-site verification and positioning, leveraging LRTK (an iPhone-mounted GNSS high-precision positioning device) lets you easily obtain high-accuracy location information for planned plants and existing equipment, aiding design studies and the identification of loss factors. By combining the ability to interpret generation losses in PVSyst with a measurement environment that accurately captures the site, generation forecasts become more practical and usable for decision making.