Abstract: A computer-implemented system and method for efficiently performing area-to-point conversion of satellite imagery for photovoltaic power generation fleet output estimation is provided. Satellite imagery data of overhead sky clearness for a geographic region is accessed. Pixels within the satellite imagery data corresponding to a bounded area are identified. Each pixel represents collective irradiance within the bounded area. An area clearness index for the bounded area is set as an average of point clearness indexes derived from the collective irradiance for each point. A variance of the area clearness index is expressed as an average of the variance of the point clearness indexes. The variance of the area clearness index is proportioned to an area metric corresponding to each pixel's physical coverage area. A variance of the point clearness index is determined for one point as a ratio of the variance of the area clearness index and each pixel's physical coverage.