> ## 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.

# Uncertainty Analysis

> Configure P-value selections and uncertainty parameters for probabilistic energy estimates

The Uncertainty Analysis page allows you to configure probability exceedance values (P-values) and uncertainty input parameters for generating probabilistic energy estimates. This page is accessed via the "Show Uncertainty Analysis" button on the [Simulation Settings](/user-guide/ui/simulation-settings) page.

<Frame caption="Uncertainty Analysis Configuration">
  <img src="https://mintcdn.com/terabaseenergy/NaTzh7AscdffXqcV/images/uncertainty-analysis-ui.png?fit=max&auto=format&n=NaTzh7AscdffXqcV&q=85&s=3e5600c61c0aa372fc7283c61f564b59" alt="Uncertainty Analysis Configuration" width="2048" height="844" data-path="images/uncertainty-analysis-ui.png" />
</Frame>

## Overview

The Uncertainty Analysis page is organized into the following sections:

1. **P-Value Selection** — Choose which probability exceedance values to calculate (P99, P95, P90, P75, P10) plus a custom P-value option.
2. **Probability Distribution Chart** — Visual representation of the GHI probability distribution with selected P-values marked.
3. **Uncertainty Inputs** — Define the uncertainty percentages for various input parameters that contribute to the combined uncertainty.

***

## User Inputs (P-Value Selection)

<table>
  <colgroup>
    <col style={{width: "4%"}} />

    <col style={{width: "18%"}} />

    <col style={{width: "10%"}} />

    <col style={{width: "6%"}} />

    <col style={{width: "44%"}} />

    <col style={{width: "18%"}} />
  </colgroup>

  <thead>
    <tr>
      <th>#</th>
      <th>Input</th>
      <th>Type</th>
      <th>Units</th>
      <th>Description</th>
      <th>Related Documentation</th>
    </tr>
  </thead>

  <tbody>
    <tr>
      <td>**1**</td>
      <td>**P 99**</td>
      <td>Checkbox</td>
      <td>—</td>
      <td>Include P99 in results. P99 represents the energy value exceeded with 99% probability — a conservative estimate for financing scenarios.</td>
      <td>[Uncertainty Analysis](/user-guide/results/uncertainty-analysis)</td>
    </tr>

    <tr>
      <td>**2**</td>
      <td>**P 95**</td>
      <td>Checkbox</td>
      <td>—</td>
      <td>Include P95 in results. P95 represents the energy value exceeded with 95% probability.</td>
      <td>[Uncertainty Analysis](/user-guide/results/uncertainty-analysis)</td>
    </tr>

    <tr>
      <td>**3**</td>
      <td>**P 90**</td>
      <td>Checkbox</td>
      <td>—</td>
      <td>Include P90 in results. P90 represents the energy value exceeded with 90% probability — commonly used for debt sizing in project finance.</td>
      <td>[Uncertainty Analysis](/user-guide/results/uncertainty-analysis)</td>
    </tr>

    <tr>
      <td>**4**</td>
      <td>**P 75**</td>
      <td>Checkbox</td>
      <td>—</td>
      <td>Include P75 in results. P75 represents the energy value exceeded with 75% probability.</td>
      <td>[Uncertainty Analysis](/user-guide/results/uncertainty-analysis)</td>
    </tr>

    <tr>
      <td>**5**</td>
      <td>**P 10**</td>
      <td>Checkbox</td>
      <td>—</td>
      <td>Include P10 in results. P10 represents the energy value exceeded with 10% probability — an optimistic upside estimate.</td>
      <td>[Uncertainty Analysis](/user-guide/results/uncertainty-analysis)</td>
    </tr>

    <tr>
      <td>**6**</td>
      <td>**Custom P** (Checkbox)</td>
      <td>Checkbox</td>
      <td>—</td>
      <td>Enable a custom probability exceedance value. When checked, enter the desired P-value in the adjacent text field.</td>
      <td>—</td>
    </tr>

    <tr>
      <td>**7**</td>
      <td>**Custom P** (Value)</td>
      <td>Text Field</td>
      <td>—</td>
      <td>Enter a custom probability exceedance percentage (1-99). The corresponding energy value will be calculated and included in results.</td>
      <td>—</td>
    </tr>
  </tbody>
</table>

<Note>
  A maximum of **four (4) P-values** can be selected simultaneously. P50 is always calculated and shown as the base case (50% probability of exceedance).
</Note>

***

## User Inputs (Uncertainty Parameters)

<table>
  <colgroup>
    <col style={{width: "4%"}} />

    <col style={{width: "18%"}} />

    <col style={{width: "10%"}} />

    <col style={{width: "6%"}} />

    <col style={{width: "44%"}} />

    <col style={{width: "18%"}} />
  </colgroup>

  <thead>
    <tr>
      <th>#</th>
      <th>Input</th>
      <th>Type</th>
      <th>Units</th>
      <th>Description</th>
      <th>Related Documentation</th>
    </tr>
  </thead>

  <tbody>
    <tr>
      <td>**8**</td>
      <td>**Spatial Variability**</td>
      <td>Text Field</td>
      <td>%</td>
      <td>Uncertainty due to differences between the weather data source location and the actual project site. Accounts for micro-climate variations and distance from measurement stations.</td>
      <td>[Uncertainty Analysis](/user-guide/results/uncertainty-analysis)</td>
    </tr>

    <tr>
      <td>**9**</td>
      <td>**Modeling Accuracy**</td>
      <td>Text Field</td>
      <td>%</td>
      <td>Uncertainty in the energy prediction model itself, including transposition, module performance, inverter efficiency, and loss calculations.</td>
      <td>[Uncertainty Analysis](/user-guide/results/uncertainty-analysis)</td>
    </tr>

    <tr>
      <td>**10**</td>
      <td>**Interannual Variability**</td>
      <td>Text Field</td>
      <td>%</td>
      <td>Year-to-year variation in solar resource at the site. Represents the natural fluctuation in annual irradiance from typical meteorological conditions.</td>
      <td>[Uncertainty Analysis](/user-guide/results/uncertainty-analysis)</td>
    </tr>

    <tr>
      <td>**11**</td>
      <td>**Irradiance Measurement Accuracy**</td>
      <td>Text Field</td>
      <td>%</td>
      <td>Uncertainty in the source irradiance data, including sensor calibration, data processing, and satellite-derived irradiance model accuracy.</td>
      <td>[Uncertainty Analysis](/user-guide/results/uncertainty-analysis)</td>
    </tr>

    <tr>
      <td>**12**</td>
      <td>**Monitoring Period Representativeness**</td>
      <td>Text Field</td>
      <td>%</td>
      <td>Uncertainty in how representative the weather data period is of long-term conditions. Shorter monitoring periods have higher uncertainty.</td>
      <td>[Uncertainty Analysis](/user-guide/results/uncertainty-analysis)</td>
    </tr>
  </tbody>
</table>

***

## Probability Distribution Chart

The center panel displays a probability distribution curve showing the relationship between GHI values (X-axis) and probability density (Y-axis). Selected P-values are marked on the curve with colored dots, allowing visual comparison of exceedance thresholds.

***

## Returning to Simulation Settings

After configuring uncertainty parameters, click outside the uncertainty panel or use the navigation to return to the [Simulation Settings](/user-guide/ui/simulation-settings) page. Uncertainty settings are saved automatically.