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

, senior analyst, Clean Energy | August 28, 2015, 3:08 pm EDT
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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.

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  • Barbara F

    Are you folks aware that a southern CA utilitiy has inserted poison pill amendments to the otherwise wonderful SB 350? These would change the very nature of Community Choice, crippling Community Choice programs. The two CCAs already in existance are already reducing GHG emissions beyond what the investor owned utility monopolies are doing and many other communitiies around California are developing more such CCA programs. Please use your influence to get these harmful amendments, which work against the intent of SB 350, stripped from the bill. And please also oppose AB 1110 which would also harm Community Choice. More here:

  • Gavin Purchas

    Really interesting report Laura. I found the findings around greenhouse gas savings from reducing natural gas output very compelling. Building the markets for demand response, storage and regional expansion is going to take a lot of work but I am glad that UCS is on the case.
    Shame that the WSPA showed up on this chain, spouting their rhetoric and misinformation. However we have beaten them before and we will again.

  • Jeff Glass

    Horrible Horrible Legislation. An absolute 100% handover of Californians right to drive and empowers CARB to dish out heavy fines for gasoline “over-consumption” to every driver who will not meet their mandates. Take our state back from these Environmental controlling blowhards.

    • renewableguy

      You must be part of the California Drivers Alliance. Did you hear they were a front group for the fossil fuels.

      • Jeff Glass

        The California Drivers Alliance? Im just a citizen. Im not a member of any group. I also have seen first hand what CARB has already done to businesses here for the last 25 years. You must be part of the Elite Left that is bent on driving out not just every job, but also love Government oversight on each and every one of us. I do not believe Sacramento is governing our State in a responsible manner-at all

      • renewableguy

        It appears to me, you are part of the false hysteria. Its quite the exaggeration you are doing.

        Well, now the oil industry’s “California Drivers Alliance” is back and on the warpath against SB 350. They have developed a new, and even more dishonest, set of claims and scare tactics to fight this legislation, claiming that the bill will give a state agency the authority to ration gas, restrict driving, impose fines on minivans, monitor driving habits, and other claims that have no basis in fact but are intended to stir up fear and paranoia. Clearly the goal is to make voters sufficiently alarmed by this hail of misleading and just plain false information to pressure lawmakers to reject SB 350’s much-needed policies to reduce carbon pollution along with our use of price-volatile oil.

        To be absolutely clear, the state does not have the authority to implement any of these “big brother” policies that WSPA is claiming, and SB 350 doesn’t give the state this authority—but that hasn’t stopped WSPA from making up their own “facts”, including a new title for the bill.

  • Richard Solomon

    This is potentially great news. Does AB 350 provide incentives for suppliers like PG&E to increase its grid flexibility? Doesn’t it want to continue to use nat gas because it is so readily available and relatively ‘cheap,’ because it can externalize some of the costs via pollution, for them? How does this legislation motivate PG&E to move away from this model?

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      • renewableguy


    • Laura Wisland

      Thanks for the comment, Richard. UCS helped insert some language into SB 350 that
      instructs the California Public Utilities Commission and the
      California Energy Commission to consider the grid flexibility and greenhouse gas reduction benefits of using non-fossil resources for
      reliability services.