California’s Renewables Portfolio Standard (RPS) requires that, by 2020, all utilities in the state use renewables to generate at least 33 percent of the electricity provided to retail customers. Reaching this RPS target will also play a key role in determining whether or not California will meet its ambitious greenhouse gas emission reduction targets. Many other states are in similar situations: Currently California is one of 29 states (plus the District of Columbia and two U.S. territories) (1) that have RPS targets, and another eight States and two more U.S. territories (2) have adopted renewables portfolio goals (see Figure 1).

Achieving these goals will require a number of states to rely much more heavily on electricity generated by intermittent wind and solar resources. In California, wind and solar generation are expected to provide virtually all of the additional renewable energy needed to achieve the state’s RPS target (see Figure 2). Keep reading →