CAISO’s database stores fuel mix components in 5 minute values. These values are downloaded and summed and divided by 12 to obtain Megawatt-hours or MWh units for each day. These values are plotted as shown above, the upper chart displays the daily energy in MWh units. The daily fuel mix components are summed and the specific component’s precentage of the total fuel mix is calculated for each day. Five fuel mix components, biogas, biomass, small hydro, batteries, and coal that are not plotted as the values are less than 1% or so and not part of the big picture. Batteries are charged up during the day and then discharged when needed at night and so no net energy output.
Notice here that the nuclear energy component was cut back in the October and early Novenber time frame. Maybe refueling or maintenance, interesting.