California Can Reach 50% Renewable Energy: New UCS Analysis Shows Pathways and Solutions

August 28, 2015 | 3:08 pm
Laura Wisland
Former Contributor

This summer, Californians have not been able to ignore the evidence of climate change affecting our lives. Historic drought and searing temperatures have turned the Golden State into a tinderbox, escalating wildfires and placing serious strain on the state’s agricultural economy.

But not everything is dried up, on fire, or otherwise depressing. Sacramento policy makers are focused on a number of bills that will help California make real and measurable progress towards relying on cleaner, safer, and more renewable sources of energy. For example, Senate Bill 350 (De León-Leno)—the Clean Energy and Pollution Reduction Act—would increase California’s share of electricity from renewable sources to 50 percent, double energy efficiency savings, and cut California’s petroleum use in half. All of these changes would be required to happen by 2030.

How would California operate a grid with at least 50 percent renewable energy?

To get a better sense of what 50 percent renewables means for California, UCS just released an analysis led by Dr. Jimmy Nelson, Achieving 50 Percent Renewable Electricity in California, which examines how to transform California’s electricity grid to one that relies more heavily on renewable energy. The results, which used a production cost simulation model to mimic operations on the California Independent System Operator grid, demonstrate that reaching 50 percent renewable energy is possible—even faster than the timeline required in SB 350—with the technology we have in place now. The report also suggests that the state’s approach to managing the electricity grid needs should evolve to take full advantage of its low-carbon resources. (In addition to downloading a copy of the report, you can access a slide deck that summarizes the findings.)

Study concludes that it will be critical to allow non-fossil resources to provide many of the grid reliability services that generation from conventional natural gas plants provides today

It will be especially important to remove as much natural gas generation as possible from the grid in the middle of the day to make room for renewables. Without doing so, electricity produced by natural gas power plants could “crowd out” renewable generation by forcing the grid operator to curtail renewables to avoid a situation in which electricity supply exceeds demand. This can result in a missed opportunity to take full advantage of renewable generation, and creates additional greenhouse gas emissions in the process.

Source: UCS. Available online at

Source: UCS. Available online at

Key findings

  • The modeling demonstrates that California can integrate 50 percent renewable energy into our electricity mix by 2024, faster than envisioned by current state proposals.
  • If California makes no additional investment in grid flexibility beyond projected levels, raising the Renewables Portfolio Standard from 33 percent to 50 percent would reduce greenhouse gas emissions from electricity generation by 22 percent. This will be accomplished largely by producing energy with renewables instead of natural gas. But if California uses additional low or zero-carbon grid management methods such as storage, demand response, electricity exports, and more flexible operation of renewable generators, greenhouse gas emissions would drop by 27 percent.
  • The long-term goal of reducing greenhouse gas emissions in the electricity system will require integrating more renewable energy and turning down gas power plants as much as possible. The modeling results suggest that the ramping ability of existing combustion turbine and peaker gas plants will be sufficient in 2024, and installation of additional gas capacity to meet ramping needs would not be warranted.
  • If wind and solar power are allowed to play a bigger role in providing reliability services, 44 percent less renewable energy would be curtailed.
  • California can also maintain adequate grid flexibility and reliability while reducing reliance on natural gas by deploying a combination of advanced demand response—which shifts energy consumption to periods when the grid needs it the most — and energy storage like batteries. These technologies can help to reduce renewable energy curtailment and carbon emissions. In some cases, these grid management solutions deliver even greater flexibility than natural gas because they can provide grid reliability services without having to be online and simultaneously generating electricity.

As we reach 50 percent renewables on the grid and strive for even higher levels of carbon-free generation, we need to think about how renewables can help to integrate themselves into the electricity grid by providing significant grid management services as well as energy. This study helps to quantify the value of moving in that direction.

It’s certainty going to be an exciting year for California clean energy—in the next few weeks we may have legislative action on 50 percent renewables; in the coming years we also anticipate and will be working to address the other 50 percent of the grid to make sure it too is supporting efforts to reduce emissions in the electricity sector.