In 2016, the California Independent Systems Operator (ISO), which coordinates most of the electricity used in California, imported a net daily average of 201 billion kilowatthours (kWh) throughout the year from other western regions, or about 26% of its average daily demand. Those imports were supplied by the other two regions that make up the Western Interconnect (WECC). The Northwest region of WECC, which includes most of Colorado, Idaho, Nevada, Montana, Oregon, Utah, Wyoming, Washington, and a small area of northern California, supplied a daily average of 122 billion kWh. The bulk of the remaining imports to the California ISO, 68 billion kWh per day on average, came from the Southwest region of WECC, which includes much of Arizona, New Mexico, and small portions of Nevada and Texas.
Daily net interchange values reflect the sum of hourly electricity flows on transmission lines between the balancing authorities that manage regional electric production and consumption. Despite net daily imports, on an hourly basis, the California ISO sometimes exports electricity. Although in aggregate these regions reflect overall importing and exporting trends, the net flow of electricity for an individual balancing authority within each region may differ from the overall regional totals.
WECC is one of three electricity system interconnections, or networks, that cover the Lower 48 states. WECC consists of 34 electricity systems, or balancing authorities, that generally extend from the Rocky Mountains to the West Coast and include portions of Canada and Mexico. In 2016, electricity generation for the U.S. component of WECC totaled 724 billion kWh, but the system demand, or load, totaled 728 billion kWh. Mexico, Canada, and direct-current interties to other U.S. interconnections made up the net difference between total generation and demand.
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