A computer-implemented method includes receiving power measurement data for a photovoltaic (PV)-based energy generation (EG) sites, determining if cloud cover is present over the EG site based on a difference between a present and historical power output for the EG site, calculating a density of the cloud cover over the EG site based on the present and historical power outputs, and controlling load characteristics of the EG site based on the determined presence and calculated density of the cloud cover. The density of the cloud cover is based on a percentage difference in power output between the present power output and the historical power output. A vector for the cloud cover can be determined based on movement of a detected storm system with a boundary defined by a location of a plurality of EG sites, or by a movement of the cloud density from one EG site to the next.