> ## 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.

# System Nodal Data

> Detailed parameters in the System nodal data export

The System nodal data provides timestep results at the plant level, including site meteorological conditions, solar geometry, horizontal irradiance processing, and plant-level losses. This is the highest aggregation level in the nodal data hierarchy.

## Description of Nodal Data Parameters

| Parameter                                  | Units               | Description                                                                                                  |
| ------------------------------------------ | ------------------- | ------------------------------------------------------------------------------------------------------------ |
| Timestamp                                  | yyyy-MM-dd HH:mm:ss | Date and time for the calculation timestep                                                                   |
| Solar Zenith Angle                         | °                   | Angle between the sun and the vertical (zenith), where 0° is directly overhead and 90° is at the horizon     |
| Solar Azimuth Angle                        | °                   | Compass direction of the sun measured clockwise from north                                                   |
| Sunrise                                    | —                   | Boolean or time indicating sunrise occurrence for the timestep                                               |
| Sunset                                     | —                   | Boolean or time indicating sunset occurrence for the timestep                                                |
| Modelled Extraterrestrial DNI              | W/m²                | Direct normal irradiance at the top of the atmosphere, calculated from solar geometry and the solar constant |
| GHI                                        | W/m²                | Global horizontal irradiance from the weather data source                                                    |
| DHI                                        | W/m²                | Diffuse horizontal irradiance, either from weather data or calculated via decomposition model                |
| DNI                                        | W/m²                | Direct normal irradiance, either from weather data or calculated via decomposition model                     |
| BHI                                        | W/m²                | Beam horizontal irradiance, calculated as DNI × cos(zenith angle)                                            |
| Clear Sky GHI                              | W/m²                | Modeled clear sky global horizontal irradiance from the Bird clear sky model                                 |
| Clear Sky DNI                              | W/m²                | Modeled clear sky direct normal irradiance from the Bird clear sky model                                     |
| Clear Sky DHI                              | W/m²                | Modeled clear sky diffuse horizontal irradiance from the Bird clear sky model                                |
| POAI                                       | W/m²                | Representative plane-of-array irradiance at the system level, typically a capacity-weighted average          |
| Ambient Temperature                        | °C                  | Ambient air temperature from the weather data source                                                         |
| Relative Humidity                          | %                   | Relative humidity from the weather data source                                                               |
| Precipitable Water                         | cm                  | Precipitable water content in the atmospheric column, used for spectral calculations                         |
| Windspeed                                  | m/s                 | Wind speed from the weather data source, used for module temperature calculations                            |
| Wind Direction                             | °                   | Wind direction from the weather data source, measured clockwise from north                                   |
| Rainfall                                   | mm                  | Precipitation amount from the weather data source                                                            |
| Pressure Corrected Air Mass                | —                   | Optical air mass corrected for site elevation and atmospheric pressure                                       |
| Spectral Shift                             | —                   | Spectral correction factor applied at the system level to account for atmospheric spectral variations        |
| Module Surface Temperature                 | °C                  | Representative module surface temperature at the system level                                                |
| HV Transformer and Transmission Line Input | W                   | Total AC power entering the HV transformer and transmission line system from all blocks                      |
| AC Power Lost due to HV Transformer(s)     | W                   | Total power losses in all HV transformers at the plant level                                                 |
| AC Power Lost due to Transmission Line(s)  | W                   | Total power losses in transmission lines between HV transformers and the point of interconnection            |
| Transformer and Transmission Line Output   | W                   | AC power after HV transformer and transmission line losses                                                   |
| AC Power after Availability                | W                   | AC power after applying plant availability losses                                                            |
| Plant Output Limit                         | W                   | Configured maximum plant output limit at the point of interconnection, or N/A if no limit is set             |
| AC Power Lost due to Plant Output Limit    | W                   | Power curtailed due to plant output limit constraints                                                        |
| System Power Output                        | W                   | Final AC power output at the point of interconnection after all losses and curtailment                       |
| Plant Power Generated                      | W                   | Total gross AC power generated by the plant before any consumption or curtailment                            |
| Plant Power Consumed                       | W                   | Total auxiliary power consumed by the plant, including tracking motors, cooling, and monitoring systems      |