PVsyst Japanese Q&A: Solving Common Questions from Renewable Energy Designers

In solar PV design, PVsyst is the globally recognized standard simulation software. Although the interface and manuals are primarily in English because it’s developed overseas, many renewable energy designers in Japan use it for energy yield predictions and system design. However, because there is limited information in Japanese, users often get confused about how to use or configure it. In this article titled “PVsyst Japanese Q&A,” we address common questions about PVsyst and provide clear answers from a practitioner’s perspective. We cover a wide range of topics from how to use PVsyst in Japanese, setting design parameters, considering influencing factors, handling irradiance data, shading analysis with 3D scenes, interpreting output reports, installation, and ways to avoid mistakes.

Question 1: Can PVsyst be used in Japanese?

Answer: Yes, PVsyst’s interface can be switched to Japanese. PVsyst’s base language is English, but it has been translated into multiple languages such as French and German, and Japanese is included. By selecting Language under Preferences in the menu and choosing Japanese, buttons and screen displays become Japanese. Note, however, that the Japanese translation is not perfect and some expressions may sound unnatural or text may overflow in places. In such cases you can press the F9 key to temporarily switch to English to check the original text (pressing F9 again returns to the original language). Also, PVsyst’s official documentation is currently available only in English, but Japanese explanations like those on this blog can sufficiently cover practical usage.

Question 2: What kinds of simulations can PVsyst perform?

Answer: PVsyst can simulate the energy yield and various losses of photovoltaic systems in detail. Specifically, you can examine the following aspects during the design phase:

• System capacity and configuration design: You can select and combine modules and power conditioners/inverters, set the number of panels, string counts, and wiring configurations. PVsyst supports grid-connected systems (for on-site consumption or feed-in) as well as off-grid systems, and you can include batteries in the configuration when needed.

• Layout and angles: Enter tilt angles, azimuths, and layout (e.g., rooftop vs. ground-mounted, multiple-row arrays), and evaluate differences in solar reception and self-shading caused by geometric layout.

• Energy yield prediction using meteorological data: Based on local annual irradiance and temperature data, PVsyst can calculate monthly and hourly generation. In addition to annual energy balance predictions based on long-term weather data, you can obtain seasonal variations and annual performance indicators such as annual yield and performance ratio (PR).

• Analysis of loss factors: By setting factors such as degradation over time, temperature characteristics, wiring resistance losses, mismatch losses between panels, and soiling losses, you can calculate their impact on yield. In particular, you can quantify how much real-world environmental conditions like shading and temperature reduce system efficiency.

• Shading analysis: Using the 3D scene feature, you can calculate the effects of near shading from nearby objects. You can analyze the impact of buildings, trees, or adjacent panel rows on generation on a time-resolved basis and evaluate annual shading losses.

PVsyst is a powerful tool that comprehensively handles system design, environmental impacts, and output prediction. At a practical level, it is widely used from preliminary (conceptual) design through detailed design.

Question 3: What are the main design parameters to set in PVsyst?

Answer: To run accurate simulations in PVsyst, several important parameters must be set appropriately. Major design parameters include the following:

• Meteorological conditions: The foundational weather data for the simulation, such as irradiance and temperature (details below). Use reliable data corresponding to the site’s latitude and longitude.

• Location and orientation: Specify the site’s latitude, longitude, elevation, and the panel tilt and azimuth angles. These are basic parameters that determine the incident solar radiation.

• Solar module specifications: Choose module characteristics from the database—rated power, conversion efficiency, temperature coefficients, size, etc. PVsyst includes data for many major manufacturers and also allows registering new modules.

• Inverter (PCS) specifications: Input the inverter rating, European efficiency, MPPT range, and other specs. The inverter-to-module capacity ratio (DC/AC ratio) is important—check for under- or oversizing.

• System configuration: Set string lengths (number of modules in series), number of parallel strings, number of arrays per string, maximum input voltage limits, and other configuration conditions. With the proper configuration, you can verify whether the inverter input range and voltages are within acceptable limits.

• Wiring and other losses: You can set cable resistance losses (calculated from cable length and cross-sectional area), transformer losses, soiling or snow loss rates, downtime, and so on. Estimating these values to reflect real conditions improves simulation accuracy.

By setting these parameters correctly, you can obtain energy yield predictions that closely match the actual system. Especially when designing in Japan, it is important to localize parameters to the local weather and installation environment.

Question 4: What are the main factors that affect PVsyst simulation results?

Answer: The generated energy yield and performance indicators from simulations are influenced by various factors. Main factors include:

• Variability in irradiance: Naturally, more incoming solar energy yields more generation. If annual irradiance differs by 10%, the generated energy will change by roughly the same amount. Therefore, the quality and reliability of your meteorological data have a major impact on results.

• Tilt and azimuth: The amount of received irradiance changes with panel tilt and orientation. Deviating from the optimal tilt reduces annual yield. In Japan, depending on latitude, south-facing installations with a tilt around 30 degrees often maximize yield, but optimal values vary with installation conditions.

• Temperature: PV module output decreases as temperature rises. High summer temperatures increase output losses, so regions with lower average temperatures tend to have higher annual yields. PVsyst calculates temperature-related losses using module temperature coefficients and ambient temperature.

• Near shading and horizon obstructions: Surrounding buildings, trees, or other panel rows reduce irradiance, especially during morning/evening and winter. The more frequent shading is, the larger the generation loss. PVsyst can analyze near shading in detail with 3D scenes and reports annual shading losses.

• Equipment configuration and losses: Inverter sizing (oversizing), improper string layout causing generation losses, wiring resistance, soiling, and degradation over time all affect total generation. Optimizing equipment selection and configuration and minimizing loss factors is important.

Considering these factors together in simulations enables forecasts that closely reflect actual generation. For large-scale plants, a 1% difference can significantly affect financials, so properly estimating each factor is critical.

Question 5: How do you obtain meteorological data such as irradiance for PVsyst?

Answer: Long-term meteorological data (especially irradiance) for the candidate site are essential for PVsyst simulations. PVsyst integrates with several meteorological databases and supports importing external data. Common ways to obtain data include:

• Data included with PVsyst: Upon installation, PVsyst includes representative data for locations worldwide and can estimate data for specified coordinates using Meteonorm. Meteonorm, from METEOTEST in Switzerland, generates annual meteorological data for any location using data from weather stations and satellites.

• Importing externally obtained data: You can obtain satellite-derived irradiance data from sources such as SolarGIS, NASA, or JAXA, or for Japan, use NEDO’s irradiance databases (MONSOLA-11 or the newer MONSOLA-20), and import them into PVsyst in CSV or TMY formats. Data sources differ in measurement periods and resolutions, so select data with appropriate accuracy and duration.

• On-site measured data: If you have on-site pyranometer or weather station data, you can convert and use it in PVsyst format. On-site data best reflect actual conditions, but at least one year of observation is typically required for long-term predictions.

When multiple data sources are available, annual irradiance values may differ. For example, Meteonorm and NEDO may give different annual totals. Depending on project importance, it’s wise to compare multiple sources and adopt the most reasonable values. Our website’s [weather database](https://www.lefixea.com/japan/wetherdatebase) page also introduces features of each meteorological database.

Question 6: Can PVsyst simulate shading using 3D scenes?

Answer: Yes. PVsyst’s 3D scene feature can perform detailed simulations of near shading. In project detailed design mode, open the [Near Shadings] settings to access the 3D scene editor. In this editor you can perform the following settings and operations:

• Terrain settings: For uneven or gently sloped sites, you can reflect terrain elevation differences. You can import elevation data to reproduce terrain undulations or set a horizon profile to account for distant terrain shading.

• Object placement: Place buildings, trees, transmission towers, and other objects that may cast shadows onto panels in 3D space. By setting sizes (height and width) and positions according to the site layout, you can simulate the time-dependent shading. The software automatically calculates shadow lengths and positions relative to the sun’s movement and computes annual shadow impacts.

• PV plant layout: Place the panel arrays themselves in the 3D scene to evaluate self-shading. For example, for multiple-row racking, set row spacing and row heights to calculate when and how long the front rows shade the rear rows.

• Quantitative shading evaluation: From the 3D simulation, hourly generation losses are computed as a “shading factor.” PVsyst reflects this in monthly and annual shading losses in the report. If shading significantly affects generation, consider revising the layout or removing trees as potential countermeasures.

Using the 3D scene function, you can model site shading conditions in considerable detail. However, the more accurate the input data (object dimensions and positions), the more reliable the results. Recently, methods like drone surveys, laser scanning, and simple 3D surveying with smartphones are increasingly used to obtain point cloud data, which can then be used to build PVsyst-compatible scenes.

Question 7: What is included in PVsyst output reports and how should they be interpreted?

Answer: When you run a simulation in PVsyst, it generates a detailed output report. This report contains a wide range of information from project overview and system specifications to simulation results. Key items include:

• Project overview: The site location (latitude/longitude/time zone), the type of meteorological data used, whether horizon data are included, and other assumptions for the simulation are summarized.

• Summary of system specifications: The designed system configuration is listed—for example, module and inverter models and quantities, number of strings, total DC and AC capacity, oversizing ratio, and wiring loss settings.

• Simulation parameters: A list of the detailed parameters you set, such as tilt and azimuth, albedo (surface reflectance), and various loss factors (soiling loss %, downtime hours, etc.).

• Simulation result summary: Annual yield, performance ratio (PR), annual energy per kW of rated capacity (kWh/kW), and financial-relevant figures (self-consumption rate and grid feed-in where applicable) are summarized. The PR indicates the ratio of actual generation to theoretical maximum generation; a higher PR means better system efficiency.

• Monthly generation and performance: Monthly generation, PR, and average efficiencies are shown in tables and graphs so you can easily see seasonal variations and efficiency differences between summer and winter.

• Breakdown of losses: One of the most important sections, it shows a breakdown of energy losses from the moment irradiance hits the modules until energy is finally exported to the grid. For example, the flow “horizontal irradiance -> tilted-plane irradiance -> module incident energy -> DC generation -> inverter input -> AC output -> grid supply” is shown with charts indicating how much each loss—reflection, temperature, wiring, conversion, shading, etc.—contributes in percent. Reviewing this section helps identify which loss factors dominate and suggests areas for design improvement.

If you’re seeing a PVsyst report for the first time, the amount of information can be overwhelming, but focusing on the points above makes it easier to grasp the overall picture. For more detailed explanations, see our website’s [PVsyst Japanese Guide](https://www.lefixea.com/japan/pvsyst-jp), which explains each item in the simulation report.

Question 8: How do you obtain and install PVsyst?

Answer: PVsyst can be downloaded from the official website and installed. It is Windows-compatible software, and versions from PVsyst 7 onward run on Windows 10/11. Installation is the usual process—run the downloaded setup file and follow the on-screen instructions. At first launch you can select the language; choosing Japanese will display menus in Japanese (this can be changed later).

After installation you can try the software in evaluation mode (trial), but for continued use you must purchase a license. If you intend to use it operationally, obtain a license from the official site as needed.

PVsyst is relatively lightweight, but large simulations or 3D rendering depend on PC performance. At minimum, 8 GB of RAM is recommended, and a multi-core CPU improves usability. A dedicated GPU is not strictly required for 3D scenes, but having decent graphics performance makes operation smoother.

Question 9: Is PVsyst free? What is the licensing model?

Answer: PVsyst is commercial software and is generally paid. However, a free evaluation mode (trial) is provided immediately after installation. Specifically, the first 30 days after initial launch are evaluation mode, during which almost all features can be used without restriction (reports will show an “Evaluation copy” watermark, but simulations themselves are not limited). After the evaluation period ends, the software switches to demo mode, which imposes some functional restrictions.

To continue using full functionality, purchase a license from the official site and register the software using the issued activation key. The current licensing model is a term subscription (time-based license), which includes updates during the contract period. If the subscription lapses, functionality reverts to a restricted mode, but renewal allows continued use.

There are also special licenses for educational or classroom use for students in some cases. Check the official licensing information for details. In any case, it’s recommended to try the evaluation version first to assess the workflow and features, then obtain a license if needed.

Question 10: Does PVsyst support simulations with batteries or off-grid systems?

Answer: Yes. PVsyst supports simulations of systems that include batteries as well as off-grid (standalone) systems. PVsyst has a Standalone mode for off-grid systems where it calculates the overall energy balance of PV + battery + optional generator. In off-grid mode you can evaluate battery sizing seasonally and assess hours or rates of power shortage due to supply-demand imbalances.

For grid-connected systems, battery-integrated cases can also be simulated. From PVsyst 7 onward, features were added to set battery charge/discharge strategies for grid-connected systems, allowing analyses that assume operation modes like “self-consumption priority” or “peak shifting.” This lets you estimate effects such as reducing purchased power by storing daytime excess generation for nighttime use or roughly estimate backup duration during outages. However, PVsyst’s battery control logic and degradation modeling are simplified compared to specialized battery simulation tools. PVsyst is mainly a PV-focused simulation tool but is sufficiently useful for evaluating the basic effects of battery integration.

Question 11: What are common mistakes and cautions in PVsyst simulations?

Answer: Here are common mistakes made by beginners and practical cautions to keep in mind when using PVsyst.

• Incorrect location or time settings: Mistakes in site latitude/longitude or time zone can shift irradiance and daylight hours, significantly affecting results. In Japan, select the time zone “GMT+9 (JST)” and enter accurate coordinates.

• Inappropriate application of meteorological data: Using weather data from a different region or relying on monthly averages can reduce accuracy. Always use annual data close to the design location, and if possible cross-check with multiple sources.

• Equipment selection errors: Module and inverter combinations can fall outside specification limits. For example, Voc may become too high in cold conditions and exceed the inverter’s input limit, or insufficient string length may fall below the MPPT lower voltage limit. PVsyst flags such issues with warnings, but carefully check these in the design phase.

• Omitting shading considerations: If nearby shading is possible but omitted from the simulation, actual generation may be much lower than calculated. For large trees or adjacent buildings, include horizon or 3D scene shading even in a simplified form.

• Misinterpreting results: Mistaking annual total generation for first-year generation (after degradation), or misunderstanding the meaning of PR, can lead to incorrect evaluations. Understand term definitions and what each metric compares.

• Forgetting to save data: If you close PVsyst without saving a project or fail to output a report, it can be hard to reproduce results. When experimenting with small changes, save versions regularly, and keep final reports in PDF or other records.

By paying attention to these points, PVsyst can be used more reliably. Although the number of settings may feel daunting at first, with practice you’ll be able to run simulations smoothly and with fewer mistakes.

Conclusion

So far we’ve explained PVsyst’s Japanese support and usage points in a Q&A format. As a world-standard simulation tool, PVsyst can greatly improve the efficiency of PV system design and enable highly accurate predictions when used properly. However, to improve simulation accuracy, it is also important to use input data that reflect actual site conditions.

Recently, solutions like LRTK have made field surveying easier and allow rapid acquisition of accurate terrain and surrounding environment data. LRTK is a system that uses compact high-precision GNSS devices attached to smartphones and enables cm-level positioning and 3D scanning even without specialist knowledge. For example, on large PV sites, walking around with a single device can capture ground undulations and positions/heights of structures that might cast shadows as point cloud data. The obtained data can then be used to generate terrain and obstacle models for PVsyst 3D scenes, enabling more realistic simulations than before.

Incorporating these new technologies into the design process can improve planning accuracy and streamline field surveys. For renewable energy designers, combining PVsyst simulations with rapid on-site information acquisition using LRTK offers significant benefits in project reliability and efficiency. Please make active use of the latest tools to support better PV system design.