The California Independent System Operator (CAISO), the entity responsible for maintaining the balance between supply and demand for electricity throughout most of the state, operates in a setting where demand peaks in the late afternoon or early evening on summer days.
Because of differences in the hourly output of certain electricity generators, some of which are nearly constant (nuclear) and some of which can vary considerably during the day (solar, wind), output from thermal generators (mainly natural gas) and electricity imports from other regions are used to balance overall electricity supply and demand in the region.
