According to the North American Electric Reliability Corporation (NERC), the bulk power system in California is not expected to lose grid reliability this summer, despite a drought that has lowered hydroelectric generation. Overall, NERC expects more than 72 gigawatts (GW) of electric generating capacity to be available this summer in the part of the electric grid covering much of California. Summer electricity demand is expected to peak at nearly 53 GW, resulting in a reserve margin of 38% for the region.
California’s hydroelectric generation varies seasonally. From January 2014 to April 2015, hydroelectricity accounted for 6% to 14% of the state’s monthly generation, averaging near 9%.
Since early 2014, much of California has experienced extreme or exceptional drought, as measured by the U.S. Department of Agriculture’s Drought Monitor. Last year was the warmest year in California’s history and 2015 ison pace to be even warmer. The combination of low precipitation and warm weather resulted in snowpack levels reaching zero as early as late May, meaning summer water runoff from mountainous areas will be much lower than normal. This runoff is part of the water supply for hydroelectric generators in California, and water levels at several reservoirs are also significantly lower than normal throughout the state.
However, California likely has enough electric generating capacity from other sources to make up for the loss of hydroelectric generation. Each spring, NERC conducts an assessment of electric grid reliability in different areas of the United States in anticipation of peak electricity demand during summer months. In NERC’s 2015 assessment, available hydroelectric summer capacity within the California Independent System Operator (CAISO) grid was derated by 3,118 megawatts (MW). This drop in hydroelectric capacity has been partially offset by more than 2,000 MW of new renewable capacity that has come online in the state since June 2014. Increased generation from natural gas generators and increased electricity imports from surrounding areas are also expected to make up for the reduced in-state hydroelectric generation.