This paper presents a validation of the short and medium term global irradiance forecasts that are produced as part of the US Solar-Anywhere (20101 data set The short term forecasts that extend up to 6-h ahead are based upon cloud motion derived from consecutive geostationary satellite images The medium term forecasts extend up to 6 days-ahead and are modeled from gridded cloud cover forecasts from the US National Digital Forecast Database The forecast algorithms are validated against ground measurements for seven climatically distinct locations in the United States for 1 year An initial analysis of regional performance using satellite-derived irradiances as a benchmark reference is also presented (C) 2010 Elsevier Ltd All rights reserved