EclipseThis week, a total solar eclipse crossed the United States for the first time in nearly a century. The eclipse dimmed the sun for several hours, leaving utilities questioning the impact on solar power generation and whether grids are prepared to handle state policies mandating a greater renewable energy mix. As solar output plunged along the route of totality, grid operators and utilities were forced to manage the drop by bringing on greater amounts of natural gas and hydro.

Those states with high solar producing capacity, such as California and North Carolina, were significantly impacted by the path of the eclipse. California has the largest amount of installed solar capacity in the U.S. with an estimated total 14,000 MW capacity. However, during the three hour celestial event, utility-scale solar output dropped off by 3,400 MW according to the California Independent System Operator (ISO). Similarly in North Carolina, major solar power producer Duke Energy had nearly 70 percent capacity come offline during the peak eclipse.

In both cases, the grids were appropriately managed to bring backup generation from natural gas power plants and hydroelectric dams without delays or outages. Overall, the grid compensated for the major midday drop in solar output and in the process, demonstrated reliability and resiliency of power systems across the nation. Utility companies are satisfied with the result, especially since intermittent solar power is gaining momentum in the U.S. Testing the grid’s resilience is becoming increasingly important as state Renewable Portfolio Standards and greater amounts of distributed energy resources offer electricity consumers access to cleaner energy. California’s mandate to generate half its power from renewable sources by 2030 is considered ambitious, but the recent test of reliability suggests that intermittent renewables may be up to the challenge.