Free Solar Irradiance Estimator

Solar energy can be harnessed from sunlight’s radiation. However, its amount and type depend on various factors, including your latitude.

Use this tool to estimate the amount of irradiance expected in your location, which can then be multiplied by your array’s wattage to estimate energy production.

How to Use

Solar Irradiance measures the total solar energy reaching Earth per unit area during any given time period and measured in watt hours/m2, this tool calculates average daily irradiance by month using NASA CERES data over seven years based on horizontal panels, direct normal irradiance, and module efficiency to produce accurate estimates of solar irradiance.

It also accounts for other variables, including thermal insolation (how much heat the panels absorb) and shadowing from clouds, and calculates an estimate for how much sunlight will hit each panel on an ongoing basis in terms of kWh.

To use this tool, simply input your zip code and month of interest before clicking “Calculate.” The results will show average daily irradiance by month for your location as well as how much power is expected from PV panels in terms of kWh generation; to convert to W, just divide by 1000 and multiply your panel’s wattage number.

Use this tool to determine the optimal angle for your PV panels by inputting your location’s latitude and longitude, then viewing available solar angles in that location.

Solargraph has been providing tools to the solar industry for more than 15 years, using satellite data to provide free irradiance estimates to create tools more accurate than any others on the market and make it simpler for solar designers to access information required for their jobs.

If you want to gain more knowledge on how to design efficient systems and surpass your competition, reach out for a complimentary demo of our software. We can demonstrate how it can automate this process for you while giving access to more data than any other tool available today.

We have also developed a free app to calculate irradiance on-the-go. This feature is perfect for vanlife builders who need an accurate picture of how much power their panel will produce on a daily basis without waiting until home to run a sun finder. Both Apple and Google Play stores now offer this application.

Basics

This tool calculates solar irradiance for every point on the map by making use of both CPU and GPU (if available) to calculate solar radiation at each location on your map. Once complete, this layer will appear in PVGIS’ left pane of Building Footprints; if you don’t require knowledge about how much solar radiation an area receives simply uncheck the layer.

The calculation uses the Global Horizontal Irradiance model, which measures non-shaded horizontal solar irradiation at any location around the world. Its value is widely utilized for solar energy systems and consists of two parts: Beam Horizontal Irradiance (BHI), which measures direct sunlight reaching planes perpendicular to Sun’s direction; and Diffuse Horizontal Irradiance (DNI), which accounts for all incident solar power regardless of surface orientation towards or away from Sun.

BHIs are often expressed in terms of kWh/m2/year for comparison between sites and time horizons, making it simple to assess results easily across time horizons and sites. When designing solar plants for specific sites however, using the monthly average irradiance (GHI) data would prove more useful.

This measurement accounts for the impact of the Sun’s zenithal angle on how much atmosphere sunlight must pass through in order to reach Earth, known as atmospheric path length or relative air mass. If longer path lengths exist, less irradiance reaches us.

Solar Irradiance maps are created in much the same manner as weather forecast models; by combining satellite-visible imagery and meteorological data with mathematical methods to estimate radiation reaching surfaces. One popularly-used satellite-to-irradiance method is the SUNY model.

When designing a PV system, it is crucial to consider any obstructions such as trees, roofs or buildings which might cause shade. The ARKA 360 team has come up with an innovative solution: the ARKA SolarView software combines image of local landscape with data from climate station irradiance measurements in order to calculate solar potential of any site, taking into account topography, buildings orientation and any obstructions such as trees. The result provides an accurate yet quick estimation of total solar irradiance which can then be used when designing PV system designs.

Advanced

Utilizing this tool, you can obtain accurate estimates of Global Horizontal Irradiance (GHI) and Direct Normal Irradiance (DNI), which measures sunlight that directly hits a surface perpendicularly from the sun. These measurements play a key role in calculating how much solar energy your site can produce.

This tool utilizes an adapted PATMOS-X model to identify and quantify cloud properties, and NREL’s FARMS and REST2 models to calculate clear sky irradiance from cloudy skies; then outputs an accurate spatially accurate raster of annual average solar irradiance that can be used across PV design applications ranging from designing systems to estimating how many panels will be necessary for projects.

This irradiance estimator tool can accurately estimate solar irradiance under various temperature scenarios, providing an advantage over traditional physics-based models that only produce accurate results when configured according to local climate conditions.

This calculator not only allows the user to choose their ideal temperature estimation model, but it also lets them customize which time intervals will be calculated – an invaluable feature that allows for creating insolation maps spanning across different time periods.

The Diffuse Proportion parameter allows users to control how much diffuse irradiance is included in calculations. By default, values between 0.2 and 0.3 for very clear sky conditions and generally clear skies can be selected, although other value ranges are possible.

Diffuse proportion is used to adjust insolation calculations based on atmospheric conditions. It serves as an essential means of ensuring accurate calculations.

Irradiance and Temperature Estimator is a simple to use software program designed to quickly generate an accurate report of your PV systems performance, saving both time and money during PV installation projects. Perfect for both professional engineers as well as enthusiastic DIYers alike, this free tool offers easy navigation with comprehensive functionality making it the ideal companion to all your PV endeavours.

FAQ

Solar Irradiance (also referred to as Sun Exposure) refers to the power that reaches a surface per unit area from both direct and diffuse irradiance reaching that same surface. Depending on which unit of measure is being used, this term could be expressed differently; for instance kilowatt-hours per square meter per day or watts per square meter per day are two methods commonly used to measure solar irradiance.

Energy available for solar PV depends on both daily and total annual irradiance levels, making it essential that we understand these variations to effectively calculate solar energy production and optimize system design.

RatedPower’s Solar Radiation Estimator uses weather files provided by the EU JRC PVGIS online tool to estimate your solar irradiance. You can find your location’s solar irradiance estimates under the Solar Radiation tab on the results page; estimates are provided in kWh/m2/day and broken down by month and year for your convenience. Our shading calculators also use daily irradiance estimates as input when helping determine an ideal system size for you site.