> ## Documentation Index > Fetch the complete documentation index at: https://docs.plantpredict.com/llms.txt > Use this file to discover all available pages before exploring further. # Comparison between PlantPredict and PVsyst > A practical guide for engineers comparing PV performance modeling results between PVsyst and PlantPredict This guide is for engineers importing a project—or a full modeling workflow—from PVsyst to PlantPredict. It covers how to bring your PVsyst files into PlantPredict, how the two tools' structures and loss trees map onto each other, and the specific modeling differences that affect results. *** ## Importing from PVsyst ### Project import PlantPredict can import a complete PVsyst project from a ZIP file. The PVsyst project (PRJ) becomes a PlantPredict project, and each calculation variant (VC#) becomes a separate prediction. Modules (PAN), inverters (OND), weather data (MET), and shade scenes embedded in the project are imported automatically—you do not need to upload them separately. To import: on the [Project Library](/user-guide/ui/project-library), click **Import Project**, then choose **Import PVsyst ZIP (Beta)** under **Other Options** and select your ZIP file. For the full walkthrough—review screen, what gets imported, and troubleshooting—see [How to Import PVsyst Projects](/user-guide/workflows/import-pvsyst-project). ### Individual file imports If you are migrating components piece by piece, each PVsyst file type has a dedicated import path: | File | Contents | Where to import in PlantPredict | | ------ | ---------------------------- | -------------------------------------------------------------------------------------------------- | | `.PAN` | Module parameters | [Module Library → Add New Module → Upload PAN File](/user-guide/ui/add-new-module) | | `.OND` | Inverter parameters | [Inverter Library → Add New Inverter → Upload OND File](/user-guide/ui/add-new-inverter) | | `.MET` | Weather data (PVsyst v6.40+) | [Weather Library → Add New Weather → Upload Your Own Weather File](/user-guide/ui/add-new-weather) | | `.SHD` | 3D shade scene | [3D Scene → Upload SHD File](/user-guide/ui/3d-scene-overview) (Beta) | For PAN file imports, PlantPredict re-solves the single-diode parameters after import to ensure internal consistency—see [PAN file re-solve](#pan-file-re-solve) below for what to expect. A PVsyst 3D scene can contain object types PlantPredict does not support; those objects are left out of the scene that gets built. For both import paths (project ZIP file import or 3D shade scene SHD file upload), PlantPredict reports which objects were omitted, naming the object types and their counts. Any shading effect from those objects is not included in the results. *** ## Mapping from PVsyst to PlantPredict ### Plant topology PlantPredict's plant hierarchy is richer than PVsyst's. PVsyst describes a plant as a flat list of sub-arrays, each pairing an array of modules with an inverter. PlantPredict nests that same pairing—one or multiple **DC Fields** tied to one **Inverter**—inside an **Array**, and groups Arrays into **Blocks**. The DC Field is the lowest modeling unit, aggregating identical modules and strings behind a shared tracker or fixed-tilt array. Because PVsyst has no equivalent of the Array and Block layers, the importer gives each PVsyst sub-array its own Array and its own Block rather than merging them together. This keeps a one-to-one correspondence with the source variant and gives users maximum flexibility. PlantPredict also allows a single Inverter to serve heterogeneous DC Fields, differing in module, orientation, or tracker geometry. PVsyst does not: a sub-array is homogeneous by construction. An imported PVsyst project therefore always leads to one DC Field per Inverter. | PVsyst concept | PlantPredict equivalent | | ------------------------- | ------------------------------------------------------------ | | Project | Project | | Calculation variant (VC#) | Prediction | | System | Power Plant hierarchy (Blocks, Arrays, Inverters, DC Fields) | | Sub-array | DC Field + Inverter | See the [Power Plant Builder](/user-guide/ui/power-plant-builder-block) pages for the full hierarchy. ### Loss tree PVsyst reports each loss line as a percentage of the value *before* that loss is applied, so losses compound multiplicatively throughout the tree. PlantPredict divides the loss tree into four groups, each normalized by a single fixed reference quantity. Within a group, nearly every line shares that denominator and the lines are additive—you can sum them directly. The reference changes only when moving from one group to the next: | PlantPredict loss group | Reference quantity (Denominator) | | ----------------------- | ------------------------------------------ | | Irradiance Losses | Global POAI | | DC Performance Losses | DC Power at STC | | AC System Losses | Total AC Power from Inverters | | Plant-Level Losses | HV Transformer and Transmission Line Input | Total plant output is consistent between the two conventions, but line-item percentages are not directly comparable—a PVsyst line and its PlantPredict counterpart will differ in magnitude even when the underlying physics is identical. See [P50 Loss Tree](/user-guide/results/p50-loss-tree) for the per-line formulas. The table below maps common PVsyst loss diagram lines to their PlantPredict equivalents. | PVsyst loss line | PlantPredict loss line | Notes | | ------------------------------------------- | ---------------------------------------------------------- | --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | | Global incident in coll. plane | Transposition On POA | Same physics; denominators differ. | | — | 3D Correction to Transposition On POA | No PVsyst equivalent. Bay-by-bay POA correction for tracker rotation, axis tilt, and terrain slope, applied automatically when a 3D scene is enabled. See [3D Transposition](/models/transposition/3d_transposition). | | Far shadings / horizon | Far Shadings / Horizon | Beam only in PlantPredict; see [Horizon shading scope](#horizon-shading-scope). | | Near Shadings: irradiance loss | Near Shading On Global | Beam shading. | | IAM factor on global | IAM Factor On Global | Applied separately to beam, sky diffuse, and ground-reflected irradiance. | | Global Irradiance on rear side | Backside Irradiance | Bifacial only. A gain, reported as positive. | | Shadings loss on rear side | Structure Shading | Bifacial only. Rear-side loss from mounting-structure shadows. | | — | Bifaciality Factor | Bifacial only. No PVsyst equivalent—PVsyst applies the bifaciality factor at the PV conversion step rather than reporting it as a loss line. | | PV loss due to irradiance level | Module Irradiance | — | | PV loss due to temperature | Module Temperature | — | | Spectral correction | Spectral | — | | Soiling loss factor | Soiling | — | | Shadings: Electrical Loss acc. to strings | Shading Electrical Effect | See [Electrical shading models](#electrical-shading-models). | | Module quality loss | Module Quality | — | | Mismatch loss, modules and strings | Module Mismatch | In an aged PVsyst simulation this line also absorbs the mismatch from degradation dispersion. | | Mismatch for back irradiance | Backside Mismatch | Bifacial only. | | — | DC Health | No PVsyst equivalent. | | LID - Light induced degradation | Light Induced Degradation | — | | Ohmic wiring loss | DC Wiring Loss | See [DC Wiring Resistance](/models/dc-performance/dc_wiring_resistance). | | Inverter Loss during operation (efficiency) | Inverter Efficiency | — | | Inverter Loss over nominal inv. power | Inverter Limitation | Includes clipping. PVsyst splits this across several lines: nominal power, nominal voltage, max. input current, and the power and voltage thresholds. | | Auxiliaries (fans, other) | Inverter Cooling / Tracker Motor Losses / Data Acquisition | PVsyst reports auxiliaries as a single line; PlantPredict splits them by type. | | Medium voltage transfo loss | MV Transformers | Applied at the array level in PlantPredict. | | AC ohmic loss | AC Collection Lines | — | | High voltage transfo loss | HV Transformers | Applied at the plant level in PlantPredict. | | MV line ohmic loss / HV line ohmic loss | Transmission Lines | PlantPredict supports one or more HV transformers and transmission lines in series up to the point of interconnection, in a user-defined order. PVsyst models at most one HV transformer and one HV line. | | System Unavailability loss | Availability Loss | — | | Grid limitation loss | Plant Output Limitation | Plant-level. In PVsyst this appears as its own line only when **Account as separate loss** is checked; otherwise it is folded into inverter clipping. | | Module Degradation Loss (for year #N) | Degradation Loss | PVsyst reports this only when the variant is simulated for a specific operating year. In PlantPredict it appears in the DC or AC group depending on the selected degradation model. | | — | LeTID Loss | No PVsyst equivalent. Enabled on [Simulation Settings](/user-guide/ui/simulation-settings). | ### Shade factor table To compare direct beam shading results line-by-line against PVsyst, PlantPredict exports a **Beam Irradiance Shade Factor Table** on the same 10° sun height × 20° azimuth grid PVsyst reports, from the [3D Scene](/user-guide/ui/3d-scene-overview) page via **Export Shade Factor Table**. Availability depends on the tracking and binning configuration—see [3D Scene](/user-guide/ui/3d-scene-overview) for the current conditions. ### Electrical shading models Both tools split the beam shading loss into an irradiance component and an electrical effect of shade component. PVsyst offers **No shadings**, **Linear shadings** (irradiance deficit only, no mismatch), **According to module strings / partitions** (mismatch computed from the string layout), and **Module Layout**. Module Layout is not available above 5 MWp, so it is not practical for realistic utility-scale power plants. PlantPredict offers four models: **None**, **Linear**, **Fractional**, and **Step Fractional** (V12+, 3D Site Level shading algorithm only). | PVsyst | PlantPredict | Notes | | ---------------------------------------- | ------------------------------------------ | ----------------------------------------------------------------------- | | No shadings | None | Shading is ignored entirely. | | Linear shadings | Linear | Electrical factor equals the beam shading factor. Recommended for CdTe. | | According to module strings / Partitions | Step Fractional (V12+) / Fractional (V11-) | Closest analogues; the formulations differ. | | Module Layout | — | Not available above 5 MWp. | The models are formulated differently in each tool, so their percentage inputs are not interchangeable. See [Electrical Shading Effect](/models/shading/electrical_shading_effect) for PlantPredict's full formulation. Step Fractional (V12+) accounts for bypass-diode circuits with configurable horizontal partitions per bay, representing the non-linear response of a partially shaded module more closely than the legacy Fractional model. ### Simulation settings The most common PVsyst-to-PlantPredict setting mappings, on the [Simulation Settings](/user-guide/ui/simulation-settings) and [Environmental Conditions](/user-guide/ui/environmental-conditions) pages: | PlantPredict setting | PVsyst equivalent | Notes | | --------------------------------------------------------------------------------- | ------------------------------------------------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | | Frontside POAI / Backside POAI | Measured POA import | Both tools retro-transpose POAI back to horizontal components, but with different transposition models: PlantPredict's GTI-DIRINT iterates using **Perez**, while PVsyst uses **Hay**. Neither inversion model is user-selectable. | | Decomposition (Erbs / DIRINT / Reindl) | — | PVsyst offers no run-time choice: horizontal components are fixed when the `.MET` is built, using the source's DHI or beam where available and decomposing only when neither is present—Erbs through v8.0, ENGERER2 from v8.1. DIRINT and Reindl are not available. | | Circumsolar Treatment (Direct / Diffuse) | Circumsolar option (separate / with diffuse) | The options correspond—separate ↔ Direct, with diffuse ↔ Diffuse—but the defaults do not match: PlantPredict defaults to **Diffuse**, PVsyst to **separate** since v7.0. See [Circumsolar default treatment](#circumsolar-default-treatment). | | Transposition (Perez / Hay-Davies) | Transposition model (Perez / Hay) | Perez is the default in both tools. | | Perez Coefficients | Perez coefficient set | See [Perez coefficient set](#perez-coefficient-set). | | Incidence Angle (None / Tabular / Physical / Sandia / ASHRAE) | IAM loss factor (Fresnel / ASHRAE / user profile) | PlantPredict's **Physical** model is the Fresnel equivalent, carrying the same glass and AR-coating parameters. PVsyst's IAM profile is stored in the PAN file, so an imported module arrives with it. PlantPredict applies IAM separately to beam, sky diffuse, and ground-reflected irradiance. | | Spectral (None / Monthly Override / 1-Param Pwat or Sandia / 2-Param Pwat and AM) | Spectral correction (CREST / Sandia / FirstSolar) | Set on [Environmental Conditions](/user-guide/ui/environmental-conditions) in PlantPredict. PVsyst applies CREST and Sandia automatically by module technology and leaves FirstSolar **off by default**, so a source variant may carry no spectral correction at all. | | Module Temperature (Heat Balance / NOCT / Sandia / DC Field Defined) | Thermal loss factor ($U_c$, $U_v$) | PVsyst v8.1 moved to a transient thermal model. | | Direct Shading | Near Shadings | See [Electrical shading models](#electrical-shading-models). Disabled in PlantPredict once a 3D scene is configured—shading is then controlled from the [3D Scene](/user-guide/ui/3d-scene-overview) page. | | Diffuse Shading | Diffuse shading | — | | Number of Years | Simulation for year no *N* | PVsyst simulates one chosen operating year; PlantPredict runs a multi-year horizon in a single prediction. | | Degradation Model (Linear DC / Non-Linear DC / Linear AC / Stepped AC) | Module average degradation | From v8.0 PVsyst splits degradation 80% Imp / 20% Vmp; it was 50/50 in v7. | | Degradation Rate | Loss factor (%/year) | — | | LeTID | — | No PVsyst equivalent. | *** ## Common Comparison Pitfalls ### Azimuth convention PlantPredict measures all azimuths **clockwise from geographic North** on the 0°–360° range: 0° = North, 90° = East, 180° = South, 270° = West. PVsyst measures azimuth from the **equator-facing direction** on a signed ±180° range: 0° faces the equator—South in the northern hemisphere, North in the southern—with positive values toward West and negative toward East. PlantPredict's importer converts azimuth values automatically. ### String sizing temperature PlantPredict derives string design temperatures from ASHRAE data, using the extreme annual mean minimum dry bulb temperature at the nearest ASHRAE station by default. PVsyst applies a fixed lower temperature for the absolute voltage limit, defaulting to **−10 °C** for most European countries. Both values are editable, and both are design-only. They do produce different string counts for the same module and inverter, so verify string lengths when manually reproducing a design from one tool to the other. ### Solar position algorithm PlantPredict uses the **NREL Solar Position Algorithm** (Reda & Andreas, 2004), accurate to ±0.0003°. PVsyst uses a simplified model derived from the US Navy formulation, accurate to within a few arc-minutes. The resulting difference in sun position is negligible for energy totals but contributes to small systematic differences in time-series comparisons. ### Perez coefficient set PlantPredict offers twelve Perez coefficient sets on [Simulation Settings](/user-guide/ui/simulation-settings): five composites and seven location-specific sets from 1988. The default **PlantPredict** set corresponds to the **All Sites Composite 1990** set. PVsyst does not publish the coefficient set it uses and does not make it selectable. Since version 8.1.0, the set of Perez coefficients used by PVsyst depends on the time resolution of the simulation. At hourly resolution the two tools give very close transposition results. The differences that remain at the time-series level come mostly from the different solar position algorithms rather than from the coefficients—see [Solar position algorithm](#solar-position-algorithm). ### Circumsolar default treatment Both tools let you choose whether circumsolar irradiance is treated as direct or diffuse. PlantPredict calls the options **Direct** and **Diffuse**; PVsyst calls them **separate** and **with diffuse**. They correspond directly: separate ↔ Direct, with diffuse ↔ Diffuse. Note that under PVsyst's **separate** setting, circumsolar is treated as direct in every respect except the electrical effect of shade: it takes the beam's IAM and the beam's far and near shading factors, but it does not produce electrical shading losses. However, the defaults do not match. PVsyst's default is **separate** (since v7.0), whereas PlantPredict's default is **Diffuse**. On import, PlantPredict reads the setting from the PVsyst variant and selects the matching option, overriding the PlantPredict default if needed. This makes IAM a useful diagnostic: a gap of 0.5% or more between the two tools' IAM losses is a warning sign that they are not using the same circumsolar treatment. Treating circumsolar as diffuse generally increases IAM losses. ### Albedo definition PlantPredict uses a single albedo. The values set on [Environmental Conditions](/user-guide/ui/environmental-conditions)—read from the weather file or entered by hand—feed the transposition model's ground-reflected component and the bifacial backside calculation alike. PVsyst keeps two independent albedo inputs: the project-level albedo, which drives ground reflection on the front side, and a separate ground albedo inside the bifacial model definition. These values are independent of one another and can diverge without a warning from the tool. ### 3D transposition and orientation grouping PVsyst describes a field as a limited set of **orientations**, each carrying a single averaged axis tilt and azimuth. It groups the tables in a 3D scene into orientations automatically and computes transposition once per orientation. PlantPredict computes transposition **per bay** when a 3D scene is enabled, using each bay's own rotation angle and axis tilt, including the terrain-corrected orientation under terrain-aware backtracking. See [3D Transposition](/models/transposition/3d_transposition). This changes the bookkeeping when comparing plane-of-array irradiance. PlantPredict reports the flat-terrain result on **Transposition On POA** and the bay-level adjustment separately on **3D Correction to Transposition On POA**, which can be a gain or a loss. PVsyst has no second line—its **Global incident in coll. plane** already contains everything. To compare the two tools, take the PlantPredict POAI and apply the 3D transposition gain or loss to it; the resulting 3D-corrected POAI is what PVsyst's figure should be measured against. ### Horizon shading scope PlantPredict's far (horizon) shading applies to **beam only**: when the sun is below the interpolated horizon profile, beam irradiance is set to zero. Sky-diffuse irradiance and ground-reflected irradiance are not reduced by the horizon. PVsyst applies far shading to beam, diffuse, and albedo components. At sites with a significant horizon elevation, PlantPredict will predict more annual diffuse and reflected energy than PVsyst, and the gap grows with horizon elevation. See [Horizon Shading](/models/shading/horizon_shading). ### PAN file re-solve After importing a PAN file, PlantPredict re-solves the single-diode parameters ($I_{ph,ref}$, $I_{0,ref}$, $\gamma_{ref}$, $R_{s,ref}$, $R_{sh,ref}$) to ensure all parameters are internally consistent. The resulting values will differ slightly from PVsyst's stored values. This is expected—not an import error. ### Temperature coefficient units PVsyst PAN files store $\beta_{V_{oc}}$ in mV/°C and $\alpha_{I_{sc}}$ in mA/°C. PlantPredict stores both in %/°C. The PAN importer handles this conversion automatically. If you are entering coefficients manually, convert to %/°C before entry. ### DC wiring loss attribution PlantPredict and PVsyst differ in the order in which DC wiring (resistive) losses and inverter clipping losses are applied. PVsyst accounts DC wiring loss **before** clipping is applied. PlantPredict accounts it **after**, on the reduced current. The AC power leaving the inverter is the same either way—what changes is the split between the DC Wiring and Inverter Limitation lines. On a high DC/AC plant, expect PlantPredict to report a smaller DC Wiring loss and a correspondingly larger Inverter Limitation loss than PVsyst for the same design. ### AC ohmic loss reference power Both tools express AC collection loss as a percentage, but the reference power against which that percentage is applied can differ. PlantPredict always uses the inverter's rated AC apparent power (kVA). PVsyst lets you choose between the inverter's nominal AC output power (**PNom(Inv)**)—this option matches PlantPredict—and the array's DC nominal power at STC, times inverter efficiency (**PNomPV(ac)**). Because the percentage is converted into a wire resistance, a larger reference power means a smaller resistance and a lower resistive loss in operation. On a high DC/AC site, a PVsyst variant using PNomPV(ac) will report lower AC collection losses than the same percentage entered in PlantPredict. ### Grid limit enforcement PlantPredict applies the grid limit (LGIA) at the point of interconnection, after all AC losses, and reports it on its own **Plant Output Limitation** line. PVsyst enforces the limit at the inverter and reports it as clipping, unless **Account as separate loss** is enabled to break it out as `EGrdLim`. ### P90 / uncertainty methodology Both tools compute P-values by combining named uncertainty components via root-sum-of-squares into a single sigma, then applying a normal-distribution z-score to P50. The component taxonomies differ, so uncertainty inputs do not transfer directly between the two tools. PlantPredict's [Uncertainty Analysis](/user-guide/results/uncertainty-analysis) uses five components: interannual variability, irradiance measurement accuracy, monitoring-period representativeness, spatial variability, and modeling accuracy. PVsyst uses a different set: weather data annual variability, PV module model and parameters, inverter efficiency, soiling and module quality loss, and long-term degradation. These do not map one-to-one and must be re-entered independently in each tool. *** ## References * Reda, I., & Andreas, A. (2004). *Solar Position Algorithm for Solar Radiation Applications.* NREL/TP-560-34302. DOI: [10.2172/15003974](https://doi.org/10.2172/15003974)