Interpret data describing California's mix of energy sources, and explain "energy portfolio" as a set of sources with different tradeoffs used together.
No single energy source currently supplies all of a large state's electricity needs reliably, so states and countries rely on an energy portfolio: a mix of different sources used together, each contributing based on its own strengths. California's electricity portfolio includes natural gas, a nonrenewable fossil fuel providing reliable power on demand, solar and wind, renewable but variable, depending on sunlight and wind availability, hydroelectric power from dams, renewable but dependent on rainfall and snowpack, nuclear power, a large, steady, low-emission source, and geothermal power, using heat from underground, especially reliable in certain regions of the state.
Reading a portfolio, usually shown as a pie chart or table of percentages, means understanding what each slice contributes and why. A state might keep some natural gas capacity specifically because it can be turned on quickly when solar and wind output drops, even while investing heavily in renewable sources for other reasons; that combination of a fast-responding source alongside variable renewable sources is a deliberate portfolio strategy, not simply leftover reliance on fossil fuels.
Mastery looks like: They can read a real or sample energy portfolio, calculate combined shares, and explain why a mix of sources, not just one, is used deliberately.
Common stumbles: Assuming the source with the largest single share is automatically the most important overall; not recognizing why a fast-responding source stays in the mix even as renewables grow.