A SAM weather file is a text file that contains one year's worth of data in hourly or subhourly time steps describing the solar resource or wind resource at a particular location. A weather file may contain typical-year data that represents long-term historical data or single-year data for a particular year. The solar resource and meteorological data in a SAM weather file may have been developed from ground measurements, data from a satellite, or a combination of the two.

For more information about weather data for SAM, see the "Weather Data" chapter in SAM's Help system. The Help system is available in SAM from the software's Help menu, and as a PDF file on the Download page.

Where to find Solar Resource Data to Use with SAM

United States, North and South America, and Southern Asia

For the United States, North and South America, and Southern Asia, the NREL National Solar Radiation Database (NSRDB) is the best source of data for locations in the United States, Canada, Central and South America, Sri Lanka, India, Nepal, Bhutan, Bangladesh, and parts of Pakistan, Afghanistan, and Myanmar, and western Southeast Asia.

You can use the Download buttons on SAM's Location and Resource input page to download NSRDB data directly from SAM.

The NSRDB provides access to the latest weather files as both single-year and typical-year files from the latest PSM dataset, and from the legacy TMY2 (MTS1) and TMY3 (MTS2) datasets.

Europe, Africa, Central Asia, Southeast Asia

For Europe, Africa, Central Asia, Southeast Asia, the European Commission's Photovoltaic Geographical Information System (PVGIS) is a good source.

When you download PVGIS data, for now, the best format to use with SAM is the typical-year (TMY) in the EPW format. To use this data in SAM, after downloading the EPW files to a folder on your computer, on the Location and Resource page, click the Add/remove weather file folders button to add the folder to the list SAM uses to build the solar resource library. The files will then appear in the library where you can select them.

Other Sources of Solar Resource Data

If you know of other data sources to add to this list, please contact us.

The following sources provide free weather data:

AUSTELA Australia Single-year hourly data (select years between 1996 and 2011). Twelve locations. SAM-ready TMY3 format. Free.
EnergyPlus Global Typical-year hourly data from various sources. Over 2,100 locations. SAM-ready EPW format. Free.
Climate.OneBuilding Global Typical-year hourly data from various sources. Over 3,000 locations. SAM-ready EPW format. Free.
SIREN Toolkit Global Single-year (1979 - present) from NASA MERRA-2. Use makeweather2 program in toolkit or download separate sen_makeweather_getmerra2 package. Free.

The following sources are are for commercial data products that will work with SAM:

Clean Power Research North America Single-year data (1998 - ). Satellite-derived data. 10 km grid cells. SAM-ready TMY3 format. $$ (some free data).
SolarGIS Global Single-year and typical-year data (1994 - ). Satellite-derived data. 250 m grid cells. $$.
Meteonorm Global Single-year and typical-year data. Model-generated data from various sources. Various formats. $$.
White Box Technologies Global Single-year and typical-year data. Over 4,000 locations. Data from ASHRAE IWEC2, NSRDB, CWEC2, and CZ2010. $$.
Deutscher Wetterdienst WebWerdis Germany and other countries Single-year data. Free and $$.