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.
The most important thing to notice here is that in the summer months, natural gas usage can exceed 50% of the total fuel mix in order meet the requirements for air-conditioner use. Cutting natural gas usage in one area will only increase it in another area.