--- title: "How to read the charts" slug: "how-to-read-the-charts" description: "Explore how to read and utilize charts in the Analysis section, covering solar resources, climate data, and PV energy system insights for optimal performance." updated: 2026-03-19T11:59:17Z published: 2026-03-24T12:53:16Z canonical: "kb.solargis.com/how-to-read-the-charts" --- > ## Documentation Index > Fetch the complete documentation index at: https://kb.solargis.com/llms.txt > Use this file to discover all available pages before exploring further. # How to read the charts **In this document** We will explain how to read and work with the charts in the Analysis section. ## The project’s analysis section The Analysis section consists of the following categories: - **Solar resources:** includes data such as global horizontal and tilted irradiances, direct normal irradiation, and diffuse horizontal irradiation. - **Climate:** contains charts informing about parameters such as temperature, speed and direction of the wind, wind gusts at the surface level, and more. - **Environment:** includes information about albedo and precipitable water. If you select a PV energy system in the energy system selector, you will find additional **PV statistics**, **PV losses,**and **PV long-term degradation** categories under the Analysis section. If you requested uncertainty estimates for your project, the **Uncertainty**category will also be present. > [!WARNING] > **Important**: Be aware that the **GTI simulator** uses the **isotropic sky model** because it is simpler and works well with the view factor approach. Our **PV simulator for Evaluate** employs the **anisotropic sky model** in combination with path tracing for more accurate results. Because of this, you will see slight differences in the respective simulated **GHI values.** ## Analysis chart groups The charts were precisely crafted to depict the data in the easiest, most understandable way. Most charts in the categories are similar, with subtle differences only. This document presents the charts in their respective temporal resolution categories (yearly-montly, daily, hourly, and 15-minute charts) for better navigation. Follow these steps to work with the charts: 1. The parameters displayed are described in the **chart's legend**. In some charts, you can toggle the parameter **visibility on/off**by clicking its name in the legend. 2. **Hover over**the chart to inspect a particular timestamp’s data in the popup. 3. Some parameters may offer higher granularity data charts, e.g., daily or hourly, and you can access these in the charts menu. ![](https://cdn.document360.io/ae2d502f-6c0d-4865-a68e-43ad8da61149/Images/Documentation/image(940).png) > [!TIP] > **Note**: All charts are derived from the **same dataset**, but the values in various charts and tables may be interpreted differently to better understand the location's solar resource, climate, and environment. > [!WARNING] > **Important**: The **averages/summaries**in the charts are always calculated using the data from **COMPLETE years only!**For example, if you look at a yearly summary chart in December, the calculated data will not include data starting from January of the same year. ### Yearly-monthly charts **Monthly statistics** | | **Solar resources** | Climate | | --- | --- | --- | | **Chart included for** | GHI, DNI, D2G, GTI, Summary | TEMP, RH, TD, WBT, WS, WG, AP, PREC, Summary | Charts of this type represent **monthly averages** with **minimum**and **maximum values for each month.** The **monthly average** represents the average value per month in the given month in all years from the time series. **Minimum**and **maximum**depict the minimum and maximum values reached in the given month throughout the time series. > **Info**: If the modules used in the projectare bifacial, the system will show rear side values as well. ![](https://cdn.document360.io/ae2d502f-6c0d-4865-a68e-43ad8da61149/Images/Documentation/image-CDSQ2FEL.png) | | **Unit** | | --- | --- | | **X-axis** | Month | | **Y-axis** | Respective unit for the given parameter | #### How to use it This chart can be used to **estimate the system's minimal/maximal possible production** (min/max values) for every month in the time range. Additionally, the differences between the minimal and maximal values show the potential fluctuation of the conditions in the area. For bifacial systems, the **LTA front side** is represented in green color, and the **LTA rear side** is represented in orange color in the graph For example, during winter, solar irradiation is low. Still, the values do not differ massively and are regularly closer to the average, while in summer, the differences are more significant, and the system can experience high peaks as well as very low-production periods. In another example, you may note the temperature peaks at the location to ensure the devices such as inverters will withstand such extremes. **Interannual variability of monthly summaries/averages** | | **Solar resources** | Climate | | --- | --- | --- | | **Chart included for** | GHI, DNI, D2G, GTI | TEMP, SDWE | These charts represent **summaries**(Solar resources) or **averages**(Climate) of the given parameter, respectively, during the time period defined by the resource data. The charts display monthly **values per year.** ### ![](https://cdn.document360.io/ae2d502f-6c0d-4865-a68e-43ad8da61149/Images/Documentation/image(119).png) This chart's visualization for PREC (precipitation) and SDWE (accumulation of snow depth) differs. It is presented as a **line chart**, which better represents the accumulation effect. ![](https://cdn.document360.io/ae2d502f-6c0d-4865-a68e-43ad8da61149/Images/Documentation/image(120).png) | | **Unit** | | --- | --- | | **X-axis** | Month | | **Y-axis** | Respective unit for the given parameter | #### How to use it This chart can help you **identify the years with the best/worst conditions** for energy production and how much that deviated from the long-term average (red line). Identifying a year may help you investigate what caused such an extreme and prepare for such a scenario accordingly. Additionally, it visualizes the yearly **fluctuation**between minimal and maximal values for every month in the time series. In the case of **precipitation**and **accumulation of snow**, you can see every year’s values separately to better understand trends and examine the years with the highest deviation from the average. This can help in estimating **potential soiling losses**, designing appropriate structural supports for snow loads, and planning maintenance schedules that ensure optimal performance and longevity of the solar panels. **Yearly Time Series** | | **Solar resources** | Climate | | --- | --- | --- | | **Chart included for** | GHI, DNI, D2G, GTI | TEMP, RH, TD, WBT, WS, WG, AP, PREC | This chart represents **yearly averages**, **standard deviation**, and **mean value** of the selected parameter. The **mean value** represents the average over the whole time series, serving as a central reference point when assessing parameter values. The **standard deviation** represents average deviation from the mean, providing insight into variability or consistency over time series. ### ![](https://cdn.document360.io/ae2d502f-6c0d-4865-a68e-43ad8da61149/Images/Documentation/image(121).png) | | **Unit** | | --- | --- | | **X-axis** | Year | | **Y-axis** | Respective unit for the given parameter | #### How to use it This chart clearly shows differences from mean value year by year. The variability shows you what differences you can expect and calculate when designing your energy system. Especially in case of **temperature**, you can quickly spot which years had lowest/highest extremities and what those values were. The knowledge of **standard deviation** provides insights into variability and consistency of solar energy production, enabling more accurate predictions of energy yield. **Monthly Time Series** | | **Solar resources** | Climate | **Environment** | | --- | --- | --- | --- | | **Chart included for** | GHI, DNI, D2G, GTI | TEMP, SDWE | PWAT | This chart represents parameter’s **monthly summaries** throughout whole time series. ### ![](https://cdn.document360.io/ae2d502f-6c0d-4865-a68e-43ad8da61149/Images/Documentation/image(122).png) | | **Unit** | | --- | --- | | **X-axis** | Month and Year | | **Y-axis** | Respective unit for the given parameter | #### How to use it This chart provides valuable insights into seasonal and long-term variations in solar radiation, temperature, and other climatic factors, aiding in PV system design by allowing for the optimization of panel orientation, sizing of the system to match energy demand patterns, and enhancing the accuracy of energy yield predictions and financial models. **Monthly and yearly summaries/averages table** | | **Solar resources** | Climate | | --- | --- | --- | | **Chart included for** | GHI, DNI, D2G, GTI | TEMP, RH, TD, WBT, WS, WG, AP, PREC | The **Monthly and yearly summaries/averages** table visually represent the monthly values for each year in the range. The table cells are visualized as a **heatmap**to see the differences. This can be used as a reference to quickly spot the months with the highest/lowest rates. 1. Summary for the given **month**in the given **year**. 2. Summary for the **whole year.** 3. LTA (long-term average) value for the given month. ### ![](https://cdn.document360.io/ae2d502f-6c0d-4865-a68e-43ad8da61149/Images/Documentation/image(396).png) | | **Unit** | | --- | --- | | **X-axis (top)** | Months | | **X-axis (bottom)** | Long term average (LTA) | | **Y-axis (left)** | Year | | **Y-axis (right)** | Summary/Average for the whole year | #### How to use it This histogram table provides a quick **visual assessment** of the most productive months and seasonal differences and helps estimate the highest/lowest energy yield periods. Additionally, it can help you determine the best time of the year for planned maintenance or show you when the system can work under more optimal conditions due to lower temperatures despite lower solar irradiance. ### Daily charts **Monthly histogram of daily values** | | **Solar resources** | Climate | | --- | --- | --- | | **Chart included for** | GHI, DNI, D2G, GTI | TEMP, RH, TD, WBT, WS, WG, AP, PREC | The chart represents histograms of daily **summaries/averages** of the given parameter, respectively. Columns depict the percentage of days the parameter was within a certain range, and the black line shows the cumulative distribution function. The percentiles are displayed with dark grey and light grey color bands, respectively. ## ![](https://cdn.document360.io/ae2d502f-6c0d-4865-a68e-43ad8da61149/Images/Documentation/image-4OFPDT86.png) | | **Unit** | | --- | --- | | **X-axis** | Respective parameter values | | **Y-axis (left)** | Percentage value of days in the range (columns) | | **Y-axis (right)** | Cumulative distribution function (black line) | #### How to use it This chart reveals **patterns**of variability and extremes, helping to optimize system sizing, anticipate periods of over- or under-production every month, and plan for energy storage or supplementary power needs. Different percentiles, such as **p90, p50,**and **p75**, provide a range of probabilistic energy yield estimates, helping in PV system design planning by offering a more comprehensive understanding of potential energy production under various conditions, facilitating risk assessment, financial modeling, and ensuring that the system is resilient to variations in solar resource availability. ### Hourly charts **Hourly statistics by month** | | **Solar resources** | Climate | | --- | --- | --- | | **Chart included for** | GHI, DNI, D2G, GTI | TEMP, RH, TD, WBT, WS, WG, AP, PREC | The chart shows the hourly range for **98%** of days in the month (p01-p99), the hourly range for **80%** of days in the month (p10-p90), and the **hourly average** in the given month (blue line). ### ![](https://cdn.document360.io/ae2d502f-6c0d-4865-a68e-43ad8da61149/Images/Documentation/image-6BNRQARN.png) | | **Unit** | | --- | --- | | **X-axis** | Hour of the day | | **Y-axis** | Respective parameter values | #### How to use it This chart provides detailed insights into the variability and reliability of solar energy production on an hourly basis. These charts benefit PV system design by allowing you to: - **Identify Peak and Off-Peak Periods:** Understand typical and extreme ranges of solar radiation and energy production throughout the day, helping to optimize system performance and align with energy demand patterns. - **Plan for Energy Storage and Backup:** Assess the need for and size of energy storage solutions and backup power systems to maintain a stable energy supply during periods of low solar output. **Hourly statistics data tables** The hourly data visualization tables are created in the same way as the monthly and yearly summaries tables. They give you a **color-coded view** of the monthly parameter **summary/average per hour.** 1. The **average**(Climate) or **summary**(solar resource) at the given hour in the month. 2. **LTA**(Climate) or **summary**(solar resource) per month. ### ![](https://cdn.document360.io/ae2d502f-6c0d-4865-a68e-43ad8da61149/Images/Documentation/image(397).png) | | **Unit** | | --- | --- | | **X-axis (bottom)** | Summary (solar resource) or LTA (Climate) | | **X-axis** **(top)** | Month | | **Y-axis** | Hour of the day | #### How to use it The **temperature heatmap** table can help you identify times when overheating can occur and limits can be exceeded or spot the coolest periods during the day in the given month. You can use this information to perform maximum demand tests or introduce relevant system protection. **Monthly histogram of hourly values** | | **Solar resources** | Climate | | --- | --- | --- | | **Chart included for** | GHI, DNI, D2G, GTI | TEMP, RH, TD, WBT, WS, WG, AP, PREC | The chart represents **histograms of hourly averages** of the given parameter with **percentiles**stated in the text. The **grey area** with middle line depicts **average**and **standard deviation** from it, and the black line shows the cumulative distribution function. This chart’s availability depends on location and its dataset granularity. The values written inside the chart show the **percentiles.** ### ![](https://cdn.document360.io/ae2d502f-6c0d-4865-a68e-43ad8da61149/Images/Documentation/image(259).png) | | **Unit** | | --- | --- | | **X-axis** | Respective parameter values | | **Y-axis** | Percentage of days | #### How to use it The x-axis of chart indicates **how far values go** in every month and they depict instant values not averages. If, for example, values in a chart representing **July**in the **northern hemisphere** (summer month) are mostly in the **lower range**, it may indicate that it is often cloudy and that, despite summer, energy production is much lower than expected. If charts are almost **identical for all months** it may indicate that energy production could be consistent throughout whole year (e.g., desert areas in Africa). ### 15-minute values charts **Monthly histogram of 15-minute values** | | **Solar resources** | Climate | | --- | --- | --- | | **Chart included for** | GHI, DNI, GTI | N/A | The chart represents **histograms of daily averages** of the given parameter with **percentiles**stated in the text. The **grey area** with middle line depicts **average**and **standard deviation** from it. This chart’s availability depends on location and its dataset granularity. The values written inside the chart show the **percentiles.** ### ![](https://cdn.document360.io/ae2d502f-6c0d-4865-a68e-43ad8da61149/Images/Documentation/image-A5FWCRQ8.png) | | **Unit** | | --- | --- | | **X-axis** | Respective parameter values | | **Y-axis** | Percentage of days | #### How to use it The x-axis of chart indicates **how far values go** in every month and they depict instant values not averages. If, for example, values in a chart representing **July**in the **northern hemisphere** (summer month) are mostly in the **lower range**, it may indicate that it is often cloudy and that, despite summer, energy production is much lower than expected. If charts are almost **identical for all months** it may indicate that energy production could be consistent throughout whole year (e.g., desert areas in Africa). **Monthly histogram of 15-minute signed/unsigned changes** | | **Solar resources** | Climate | | --- | --- | --- | | **Chart included for** | GHI, DNI, GTI | N/A | The charts represent histograms of 15-minute **signed**(positive and negative values)/**unsigned**(absolute value of positive and negative values) parameter changes respectively. It depicts percentage of days parameter changed by a certain amount. ### ![](https://cdn.document360.io/ae2d502f-6c0d-4865-a68e-43ad8da61149/Images/Documentation/image(128).png) | | **Unit** | | --- | --- | | **X-axis** | Respective parameter values | | **Y-axis** | Percentage of days | #### How to use it You can use the **signed chart** to note the range the values reach in every month. Values closer to zero indicate low fluctuation in values, while a wider chart shows the values changing more significantly within a single month. This knowledge may help you to determine what **battery size** would be appropriate for the location. ### Other charts **Wind speed and wind direction** This chart illustrates the direction and speed of the wind at the location. It is represented by a **circle**depicting the **directions**(North, East, South, West) with intermediary directions in between. Different **colors represent** different **wind speeds** (1), and the **direction** is indicated by its placement within the chart. ![](https://cdn.document360.io/ae2d502f-6c0d-4865-a68e-43ad8da61149/Images/Documentation/image(398).png) **Ground surface albedo** The chart represents the monthly ground surface albedo averages for the whole time series and is available under the **environmental category** only. ![](https://cdn.document360.io/ae2d502f-6c0d-4865-a68e-43ad8da61149/Images/Documentation/image(130).png) | | **Unit** | | --- | --- | | **X-axis** | Months | | **Y-axis** | Ground albedo | #### How to use it Albedo values can help you establish the reflectivity of the surrounding area and make more informed decisions when selecting the PV module type. ## PV energy system charts If a PV energy system is selected for the project, the **PV statistics, PV system loss**, and **PV long-term degradation** charts will be available. They are calculated using our advanced **PV Simulator**, considering many factors, such as inverter and array parameters, cabling losses, shading, or snow and soil losses. They provide detailed insight into the feasibility of the power plan at the selected location. Details about the PV energy system charts are outlined in [this](/v1/docs/energy-system-statistics-losses-and-long-term-degradation)document.