The Renewable Resource Data Center (RReDC) is managed by the Department of Energy and "provides information on several types of renewable energy resources in the United States, in the form of publications, data, and maps." The National Solar Radiation Data Base (NSRDB) contains data from 1961-1990 on solar radiation and supplementary meteorological data from 237 sites in the US, as well as Guam and Puerto Rico. Data includes daily statistics files, hourly data files, a solar radiation data manual for buildings and for flat-plate and concentrating collectors, typical meteorological year (tmy) data, and resource maps. The page also has an online user manual to help decipher and best utilize the files.