There are several solar power plants in the Mojave Desert which supply power to the electricity grid. Insolation (solar radiation) in the Mojave Desert is among the best available in the United States, and some significant population centers are located in the area. These plants can generally be built in a few years because solar plants are built almost entirely with modular, readily available materials. Solar Energy Generating Systems (SEGS) is the name given to nine solar power plants in the Mojave Desert which were built in the 1980s, the first commercial solar plant. These plants have a combined capacity of 354 megawatts (MW) which made them the largest solar power installation in the world, until Ivanpah Solar Power Facility was finished in 2014.