Global Horizontal Irradiance: The total amount of solar radiation that is received per unit area by a surface that is always positioned in a horizontal manner.
Direct Normal Irradiance (DNI)
Direct Normal Irradiance: The total amount of solar radiation received per unit area by a surface that is always perpendicular to the sun rays that come in a straight line from the direction of the sun at its current position in the sky.
Average Tilt at Latitude (ATaL)
Average Tilt at Latitude: The total amount of solar radiation received per unit area by a surface that is tilted toward the equator at an angle equal to the current latitude. ATaL will often produce the optimum energy output.
Solar Radiation Levels in 20621
Solar Radiation Data in 20621
See the chart below for monthly solar radiation levels in 20621.
* Amounts listed in kWh/m2/day (kilowatt hours per square meter per day)
Solar Radiation Analysis for 20621
Sorry, it is not possible to complete our solar radiation analysis for 20621 at this time.
Historical solar radiation data for 20621 is not currently available.
Please check back later.
Solar Power Comparison: 20621 vs. the U.S.
Solar Power Levels in 20621
Sorry, solar radiation data for 20621 is not currently available. Please try again later.
Solar Power: 20621 vs. the U.S.
Below is a month-by-month comparison of how average 20621 solar radiation levels compare to average levels in a city with historcially high levels (NV) and a city with historically low levels (WA). 
→ k/m/d = kWh/m2/day = kilowatt hours per square meter per day.
→ Values listed as 0 (zero) are not available (N/A).