The accuracy of satellite-estimated surface solar irradiance and the relationship between irradiance at pairs of locations and distance between the pairs were examined. Daily measured and satellite-estimated irradiances were available for a 2–3 year period from 20 Texas locations. For the distance analysis, irradiances were normalized as a percentage of daily potential surface irradiance. In comparing the measured and satellite-estimated irradiances, the bias (the mean of satellite-estimated minus measured irradiance differences for the period of record) increased from ±1 MJ m−2 d−1 in the northern two-thirds of Texas to 2 MJ m−2 d−1 in the southern portion. The root-mean-square errors (RMSEs) between irradiances averaged 2.5 MJ m−2 d−1, which is 12% of the mean annual statewide potential surface-irradiance. Errors were at a maximum in the winter and a minimum in the summer. Between measured irradiances at pairs of locations, RMSEs increased rapidly for the first 200 km distance between the pairs... Abstract The accuracy of satellite-estimated surface solar irradiance and the relationship between irradiance at pairs of locations and distance between the pairs were examined. Daily measured and satellite-estimated irradiances were available for a 2–3 year period from 20 Texas locations. For the distance analysis, irradiances were normalized as a percentage of daily potential surface irradiance. In comparing the measured and satellite-estimated irradiances, the bias (the mean of satellite-estimated minus measured irradiance differences for the period of record) increased from ±1 MJ m−2 d−1 in the northern two-thirds of Texas to 2 MJ m−2 d−1 in the southern portion. The root-mean-square errors (RMSEs) between irradiances averaged 2.5 MJ m−2 d−1, which is 12% of the mean annual statewide potential surface-irradiance. Errors were at a maximum in the winter and a minimum in the summer. Between measured irradiances at pairs of locations, RMSEs increased rapidly for the first 200 km distance between the pairs...