【How to Calculate Annual Energy Production in PVSyst｜5 Setup Steps】

Table of Contents

• Basics to understand before calculating annual energy production with PVSyst

• Step 1 Create the project and determine the site conditions

• Step 2 Select weather data to lay the foundation for the calculation

• Step 3 Enter azimuth, tilt, and capacity configuration

• Step 4 Reflect loss conditions and the effects of shading

• Step 5 Run the simulation and check the annual energy production

• How to interpret annual energy production

• Common pitfalls in PVSyst annual energy production calculations

• Summary

Basics to Understand Before Calculating Annual Energy Production in PVSyst

When calculating annual energy production in PVSyst, the first thing to understand is that the annual yield is not a number that will be automatically and correctly produced simply by entering the system capacity. The actual calculation builds up conditions such as location, weather, the orientation and tilt of the receiving surface, electrical configuration, various losses like temperature and wiring, and far-field and near-field shading. The software stores location and weather data at the project level and is structured so you can create and compare multiple cases with different conditions within a project, and the detailed annual simulation is carried out on an hourly basis. In other words, if you want to obtain an accurate annual energy estimate, the most important step is to first decide how closely and to what extent you will align each condition with reality.

pvsyst.com

pvsyst.com

Many search users want to quickly know only the annual generation figure. However, in practice, if you cannot explain which assumptions produced that figure, it becomes difficult to use for design reviews or internal explanations. For example, even with the same installed capacity, the amount of incident sunlight changes if the orientation or tilt changes, and if soiling, temperature, wiring, mismatch, or the treatment of shading are handled too optimistically, the apparent large generation can diverge significantly from actual operation. That is why, when using PVSyst, it is important not just to follow the screens in order but to proceed while understanding which settings strongly affect the annual energy yield.

pvsyst.com

pvsyst.com

This article assumes a typical grid-connected project and explains a practical workflow for calculating annual energy production divided into five steps. First, perform a calculation once under minimal conditions, then proceed by gradually adding shading and losses; this approach makes it easier to trace why the numbers changed along the way. This procedure is also presented in the official tutorial as creating an initial basic case and then incrementally adding conditions such as shading and detailed losses.

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Step 1 Create the Project and Set the Site Conditions

The first step is to create a new project and correctly set the site location. In PVSyst, the project serves as the foundation that contains the site information and meteorological data. If this is ambiguous, then no matter how carefully you enter the system parameters later, the assumptions for annual energy production will be shifted. Site settings are not merely an address note but an important item used to calculate the sun's position throughout the year based on latitude and longitude. Therefore, you should first confirm where to place the center of the candidate site and how far it is from the actual planned site.

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A common practical mistake is to take a representative location from a neighboring city at face value and not fully account for differences in elevation, terrain, and weather. Even if areas look close on a regional scale, coastal and inland areas and highlands and lowlands can have different patterns of solar radiation and temperature. First, it is important to decide on a single location for the project and build the project with that site as the reference. Even if you want to compare multiple candidate sites, proceeding roughly with one representative point is not advisable; treating the assumptions separately for each candidate will reduce rework in later stages. The software is also designed around a site as the core, enabling comparisons of multiple cases.

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Also, the way you name projects is surprisingly important. Including not only the project name but also the site name, expected capacity, and design stage makes later comparisons less confusing. This is because, for annual energy production calculations, similar files tend to proliferate—initial-stage estimates, recalculations after layout implementation, and submission figures adjusted for losses, for example. If naming is done carelessly, it becomes unclear which figures are the latest and misuse can easily occur when sharing internally. Because PVSyst can manage multiple case variants within a single project, deciding on naming rules in advance stabilizes operations.

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Step 2 Choose meteorological data to establish the basis for calculations

The weather data has a major impact on the accuracy of annual energy production. In PVSyst, annual simulations are run using meteorological data tied to the site. If available meteorological files exist, you can select from those options, and if there is no usable data nearby, a workflow is provided to generate synthetic time-series data to start the project. In other words, choosing the weather data is not something to be postponed; it is the foundation of the annual energy production. If you decide this arbitrarily, even if subsequent detailed settings are correct, you will end up earnestly refining numbers that were based on different assumptions.

pvsyst.com

pvsyst.com

When choosing meteorological data, first check the distance to the site. Next, consider not only the annual solar irradiation but also temperature and wind trends, the temporal resolution, and how the data year is treated. While annual electricity generation is largely influenced by solar irradiation, differences in temperature conditions also change how output loss manifests. Furthermore, if you need to refine the treatment of shading and peak output, the temporal resolution becomes important. In practice, a realistic approach is to start with easy-to-use standard data to produce a rough estimate, then replace it with data that better matches the project and compare the differences. That makes it easier to explain how much the meteorological assumptions influence annual electricity generation.

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What's important here is not to choose a weather dataset once and leave it at that. If multiple candidate datasets exist, you should compare the annual energy production for each and check the magnitude of the differences. If the differences are small, you can conclude that for that project, orientation, shading, and loss conditions are more dominant than differences between weather sources. Conversely, if the differences are large, the project has significant uncertainty in its meteorological assumptions. PVSyst also provides mechanisms to compare multiple weather files and multiple locations, so performing a sensitivity check before narrowing the submission figures to a single value will increase your credibility.

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Also, when explaining annual power generation, it is important not to treat the single-year calculation result as an absolute value. One approach is to use the normal simulation result as a baseline, and then proceed to an evaluation that takes uncertainty into account. The official help indicates that evaluations from P50 to P90 are performed after the initial simulation, and that P50 is treated as the default value of the normal simulation result. In situations where strictness is required in how annual power generation is presented, it is easier to organize by first calculating the normal annual generation and then separating how much uncertainty to incorporate.

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Step 3 Enter orientation, tilt, and capacity configuration

Once the meteorological data are set, next enter the orientation and tilt of the receiving surface and the system capacity configuration. For annual energy production calculations, this is the part that most directly affects the numbers. Whether the surface is close to south-facing or oriented east–west, and whether the tilt is shallow or steep, changes both the total solar irradiance received and its hourly distribution. In PVSyst project design, the workflow is to define the receiving surface orientation for each case and then define the system conditions. In other words, when calculating annual energy production, azimuth and tilt are not just input fields but the very framework of the calculation.

pvsyst.com

pvsyst.com

The key here is not to try to aim for a perfect configuration from the outset. First, for the assumed mounting surface, include representative orientations and tilts, and sketch the system capacity as an initial proposal. Then review the number of series and parallel connections, the capacity ratio, and how the receiving surface is divided; doing this makes it easier to understand how the results change. What field staff often stumble over is cramming lots of detailed conditions into the first run, which makes it impossible to tell which setting caused the results to improve or worsen. Start by creating a minimal baseline case, and then add conditions afterward so you can more easily track changes in annual energy production.

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Also, when entering the equipment configuration, you need to pay attention not only to capacity but also to electrical compatibility. PVSyst checks the consistency of the settings and has a mechanism to distinguish and display notes for values within acceptable ranges and problems that will stop the simulation. Therefore, after finishing inputting the numbers, do not proceed directly to the Calculate button; always read the warnings and confirm that the voltage and configuration conditions are feasible. The annual energy production can ultimately be seen as a single figure, but if the assumptions underpinning that number are unreasonable, the result will be difficult to use for comparisons or submissions.

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When a project has multiple solar-facing surfaces, it is also important not to consolidate them too much into a single averaged condition. If each roof surface has a different azimuth and tilt, or if a developed site has different conditions for each terrace, it is closer to reality to represent each separately. The assumption of a single averaged plane is convenient for simple comparisons, but as you approach detailed design it becomes a source of error. In particular, treating surfaces that produce more output in the morning together with surfaces that produce more output in the afternoon will change how peak output appears. If you want to be conscious not only of annual generation but also of time-of-day output characteristics, it is essential to incorporate the differences between surfaces into the conditions.

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Step 4 Reflect loss conditions and shadow effects

When calculating annual energy production with PVSyst, the loss settings are what beginners are most likely to underestimate. In practice, the solar radiation incident on the receiving surface does not directly become the annual energy production. Multiple losses—output decrease due to temperature rise, wiring losses, quality variability, mismatch, angle-of-incidence losses, soiling, distant shading, nearby shading, and so on—accumulate to produce the final figure. The official help also explains that at the detailed design stage you can add and analyze these small effects, and the results are useful for identifying weak points in the loss diagram. Bringing the annual energy production closer to reality is, in other words, the process of determining how reasonably to reflect these losses.

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When setting losses, the important point is not to take the approach that overestimating everything is safer. Stacking overly conservative figures can unnecessarily reduce a project's appeal. Conversely, underestimating soiling, temperature, or wiring losses can create a large gap between favorable desk calculations and actual performance. Therefore, it is practical to first calculate using common initial values, and then overwrite individual items to match site conditions and installation conditions. In particular, when comparing multiple projects, separating losses that are common across projects from those that are specific to each project makes it easier to clarify what the numbers mean.

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Handling shadows requires extra care. Shadows from distant mountains, wooded areas, or nearby buildings differ in both the way they should be considered and in how they affect the site compared with shadows from close equipment or structures. PVSyst supports far-field shading settings and 3D near-field shading representation, and the accuracy of near-field shading improves the more realistically you model the scene. In other words, when calculating annual energy production for a project likely to be affected by shading, you should not stop at simple azimuth and tilt alone but create separate cases that reflect shading conditions. Comparing how much the annual energy production changes before and after including shading makes it easier to decide how much time to devote to shading analysis for that project.

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For projects with significant partial shading, it's necessary to go beyond simply indicating whether shading is present and examine the electrical impacts as well. Shading not only reduces the amount of light received but can also spread losses through electrical mismatches. Therefore, for projects where racking is dense and inter-row shading occurs at certain times of day, you should not rely on simple settings alone and should decide early how detailed your analysis will be. Calculations of annual energy production tend to focus only on the final output number, but the greater the shading-related losses, the harder it becomes to judge validity without looking at the intermediate loss structure.

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Step 5: Run the simulation and check the annual energy generation

Once you have configured everything up to this point, run the simulation and check the annual energy production. In PVSyst, if the input values are consistent you can run the simulation, and after it completes you can review the main annual results from the results screen. The annual report always includes a loss diagram, and you can also see how impacts appear on a monthly basis. In addition, result variables can be viewed monthly, daily, and hourly, so you can drill down not only into the total annual generation but also into which seasons or times of day losses are occurring. Rather than simply noting the annual generation number and stopping, it is important to interpret the results screen and verify the appropriateness of the settings.

pvsyst.com

pvsyst.com

When looking at annual generation, it is easiest to follow the flow of first checking the total generation figure, then the specific generation per unit of installed capacity, and finally the breakdown in the loss diagram. This is because total generation alone makes it difficult to compare projects with different system sizes fairly. By looking at specific generation per unit of capacity, you can temporarily remove the effect of scale and more easily see differences in location and design conditions. And by examining the loss diagram you can see at a glance where the largest reductions occur. If you determine here whether temperature loss is large, shading is dominant, or wiring and conversion efficiency have a major impact, you will see which settings should be corrected next.

pvsyst.com

pvsyst.com

Also, it is important not to stop at a single calculation but to keep multiple cases with conditions changed step by step. For example, if you separate cases into a basic case with no shading, a case reflecting only distant shading, a case that includes near-field shading and detailed losses, and a case with different meteorological data, you can see where and by how much the annual energy production changes. PVSyst is inherently structured to compare multiple cases within a project, so if you do not use this feature, the valuable analysis history will become fragmented numbers. To produce an annual energy production figure that is persuasive in practice, it is essential to preserve not only the final value but also the comparative process that led to it.

Key Points for Interpreting Annual Power Generation

When interpreting annual generation, it is important not to evaluate it solely by total generation. The first thing to confirm is the assumptions behind that number: at which location, based on which meteorological data, with which orientation and tilt, and under what loss conditions it was derived. Next to examine are the specific yield and the performance ratio. The performance ratio is an indicator that makes it easier to compare design quality and the magnitude of losses beyond simple differences in solar irradiance conditions or installation orientation. Official documentation also explains that because the performance ratio does not directly depend on meteorological inputs or the orientation of the receiving surface, it is convenient for comparing system quality across different locations and orientations. In other words, it is important not only to consider whether annual generation is high or low, but also to use the performance ratio to assess whether that figure is appropriate for the conditions and whether losses are excessive.

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Furthermore, if you make a habit of looking at loss diagrams and identifying which losses are dominant, opportunities to improve annual energy production will become apparent. If shading losses are large, reconsidering the layout or inter-row spacing becomes an option; if temperature losses are large, you need to recheck ventilation conditions and the assumptions behind installation methods. If soiling losses are large, regional conditions and maintenance regimes should be reevaluated. In this way, if you consider reading annual energy production not as checking the final number but as understanding which loss structure produced that figure, your use of the software becomes much more practically oriented.

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When an explanation of uncertainty is required, it's easiest to organize things by using the annual generation from the standard simulation as a baseline and then adding a probabilistic perspective. Depending on the recipient or internal review, you may be asked to provide not only numbers close to the most likely value but also a conservative outlook. In that case, rather than lowering the numbers from the outset, presenting the standard calculation results separately from the uncertainty makes your explanation more consistent. Treat the initial simulation result as the baseline and then proceed to an uncertainty assessment; keeping this flow in mind makes it easier to present annual generation figures clearly.

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Common Pitfalls in Annual Energy Yield Calculations with PVSyst

One common mistake is configuring too many detailed settings from the start. While more detailed settings may seem to increase accuracy, stacking conditions without a basic case makes it impossible to trace which input affected the results. Whether the annual power generation is lower or higher than expected, if you can't identify the cause you can't make further improvements. First run with only the site, weather, azimuth, tilt, and capacity composition, then add losses and shading and compare — simply following that flow will greatly improve the clarity of how to use the tool.

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The second is treating meteorological data as if they were fixed values. Meteorological data serve as assumptions for annual power generation, and differences among candidate datasets can appear as differences in outcomes. In particular, casually adopting representative data from locations far from the site can shift the baseline for comparison. In practice, after producing a rough estimate using readily available data, it is important to check the differences using data from closer conditions or alternative datasets and assess their impact. Doing so makes it easier to explain later why those assumptions were adopted if the validity of the annual power generation is questioned.

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The third is underestimating shading. Even if a site plan looks fine, in practice surrounding terrain and equipment layout can cause losses in the morning and evening. The impact of shading affects not only total generation but also output by time of day, so it is a factor that is hard to ignore when examining grid constraints or the relationship with demand. For projects where shading could be a concern, you should always create a shading-reflected case separate from the base case and check the numerical differences. That alone raises the depth of your analysis by one level.

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The fourth is judging solely by total power generation. Even with the same annual generation, a project with larger capacity will naturally have larger figures, and if the loss structure differs the scope for improvement will change. If you make a habit of looking at total generation, specific yield, performance ratio, and loss diagrams together, comparisons between projects become less prone to inconsistency. The more perspectives you have for interpreting the numbers, the more the use of the software shifts from mere data entry to analytical work for design decisions.

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Summary

A practical workflow for calculating annual energy production with PVSyst is to understand the process as: creating the project, selecting the site, choosing the meteorological data, entering orientation, tilt, and capacity configuration, accounting for losses and shading, and interpreting the simulation results. The key point is not to aim for a perfect one-shot answer from the start, but to begin with a basic case and add conditions step by step. That way, it becomes easier to trace why the annual energy production figures changed, and the results will be more useful for internal explanations and comparative evaluations. While PVSyst is strong in detailed annual simulations and loss analysis, the quality of the input assumptions determines the quality of the results. For that reason, avoiding vagueness about local site conditions is the quickest way to improve the accuracy of desk calculations.

pvsyst.com

pvsyst.com

Especially in solar projects, when a site's elevation differences, post-development terrain, relationships with surrounding obstacles, or reference points for equipment layout are ambiguous, assumptions about shading and layout can shift, making annual power generation estimates unstable. To make annual generation calculations from design software useful in practice, it is essential to quickly and accurately capture the site's location and shape on-site. This is where LRTK is useful. As a smartphone-mounted GNSS high-precision positioning device, LRTK streamlines on-site coordinate acquisition and shape mapping, supporting improved accuracy of design assumptions. By linking desk simulations with on-site measurements, annual generation assessments become more robust in practice.