Playing The Long Game: Why States Are Turning Their Attention to Long-Duration Energy Storage

After a decade of lithium-ion procurement, the leading clean energy states are finally turning their attention to long duration energy storage. 

Although it may still seem like a new idea, state-mandated procurement of energy storage has actually been going on for more than a decade. As of mid-2024, twelve U.S. states have set intentions to procure a set amount of energy storage (usually measured in MW) by a certain date. Some of these intentions are legally mandated, while others are aspirational goals. Usually, regulated utilities are tasked with carrying out the procurement. But how these goals are to be achieved varies significantly from state to state; variables include which technologies will be incentivized, the duration of energy storage resources that will be prioritized, whether and how to incorporate equity provisions into procurement, and the role of distributed resources.  

Two states have recently incorporated new requirements for long duration energy storage (LDES) – usually defined as ranging from 8-10 hours up to multiple days – in their targets. Most energy storage systems can be qualified as short or medium duration, with typical lithium-ion battery installations designed to last about 4 hours. A 4-hour lithium-ion battery provides enough storage capacity to balance short-term fluctuations between energy supply and demand, such as during peak hours when consumption is high. But as states increasingly set aggressive decarbonization goals, the electric grids have needed to accommodate more intermittent renewable resources such as solar PV and wind. More longer duration energy storage will be needed to firm this growing renewable capacity; thus, states are shifting their attention to policies that support LDES development.  

California was the first state to adopt energy storage procurement targets in 2013 (CPUC AB 2514): 1,825 MW procured by 2020 and installed by 2024, with a specific carve-out of 500 MW for behind-the-meter storage. Impressively, California quickly met and surpassed these targets. legislation then directed the California Public Utilities Commission (CPUC) to create a strategy to set new targets for LDES. This summer, the CPUC shifted its attention to long duration energy storage, setting an additional procurement target of 2 GW of LDES, 1 GW of which is to be at least 12-hour storage and 1 GW to be multi-day storage, to be deployed between 2031 and 2037.    

Similar to California, in June of 2024, the New York State Public Service Commission (NY PSC) increased that state’s energy storage procurement targets from 3GW to 6GW by 2030. The roadmap to achieve this goal, filed by NY DPS and NYSERDA, asserts that long-duration storage (10+ hours duration) is expected to “become an important component of the long-term energy system” and recommends that NYSERDA programs “focus on supporting research, development, and demonstration of technologies that can provide reliable, zero-carbon supply.”

The New York storage roadmap notes that more than 4 GW of 8-hour storage will be needed by 2035, and 6.8 GW by 2050, and directs NYSERDA to aim for each bulk storage procurement to include a target of 20% 8+hour storage resources, resulting in 1200 MW of longer duration storage by 2030. Although 8-hour resources are generally not quite regarded as “long duration,” these medium duration resources still provide valuable grid services.  

By adopting long duration storage targets, these leading states send a powerful message to the storage industry. Yet, long duration requirements can present significant challenges for storage developers.  

The most common battery chemistry on the market today is lithium-ion technology. Lithium-ion cells can be stacked to increase the duration of the battery; however, this can quickly become too costly when durations exceed about 4 hours. Other storage technologies exist, but some, such as pumped hydro and compressed air, present environmental and land-use challenges in addition to high costs. There is a fundamental need for increased research and development of new technologies that will be cost-effective. The industry will need to examine options to bridge the gap between the increasingly long durations of storage needed and the cost/kWh for available technologies.  

What is being done to address this growing need? In addition to state targets and legislative mandates, there are efforts being made to identify and address the challenges associated with LDES. The National Consortium for the Advancement of Long Duration Energy Storage Technologies is broad coalition of stakeholders including six U.S. national laboratories. The work is led by Sandia National Laboratories and funded by the U.S. Department of Energy. The Consortium aims to examine the challenges facing LDES technologies as well as to collaboratively develop a set of actionable recommendations to address them. The labs, in partnership with a broad network of industry and community stakeholders, are working to develop a comprehensive plan for LDES commercialization that can be adopted by regions, markets, and communities across the country.  

For more information about state energy storage targets and progress toward achieving these goals, see CESA’s new Table of State Energy Storage Targets and Progress. The table shows all existing state energy procurement mandates, targets, and goals, and will be updated when states set new targets or amend their current ones to address the growing need for longer duration storage technologies. Organizations, companies and state agencies can share their perspectives and expertise to support the commercialization of LDES technologies by joining the National Consortium for the Advancement of Long Duration Energy Storage Technologies here.