Executive Summary

Energy storage systems (storage or ESS) are essential to enabling the clean energy transition and a low-carbon electric grid. A growing number of states have adopted ambitious energy and climate targets that will require them to implement a wide spectrum of well-designed policies, from market-based incentives to encourage investment in distributed energy resources (DER), to effective DER interconnection procedures that enable the rapid, efficient, and cost-effective integration of large amounts of DERs onto the grid.

Storage is a foundational tool in this transition. As renewable generation grows, storage will become an increasingly important asset for the energy management services it provides.

For example, when paired with solar, storage can provide more control over the timing and amount of energy imported from and exported to the electric grid, and can support the integration of renewables through several means, including by providing frequency regulation. Utility-scale storage can provide better resource management in states with high wind and solar deployment by mitigating the intermittency of renewable generation. And behind the meter storage can serve as a resilience resource, reduce energy costs for customers, and reduce the need for infrastructure investments necessary to serve peak demand.

These capabilities present both opportunities and challenges for storage interconnection. In order to ensure the continued safe and reliable operation of the grid, utilities must be able to trust that storage will operate as described in interconnection agreements, which allows utilities to anticipate and respond to any potential grid impacts. At the same time, interconnection customers must have access to a fair, efficient, and cost-effective interconnection process that gives them maximum freedom to interconnect their storage assets in a manner that meets their needs (e.g., having the flexibility to respond to price signals).

Most states’ existing DER interconnection procedures are not designed with storage in mind, which can create unintended time, cost, and technical barriers to storage integration. As one example, most interconnection rules either permit or require utilities to evaluate the impacts of storage on the grid with the assumption that storage systems will export their full nameplate capacity at all times. In reality, this assumption is extreme for several reasons and doesn’t reflect how storage is typically operated, thus creating an unnecessary—but solvable—barrier to storage interconnection.

In addition, interconnection procedures that aren’t tailored to serve a jurisdiction’s DER market conditions—such as when the speed of DER deployment outpaces the grid’s existing hosting capacity or utilities’ ability to process applications—can lead to serious queue backlogs or high grid upgrade fees that become barriers to interconnection.

Several states have recognized the importance of storage in supporting DER growth and achieving climate and energy goals and have updated, or are currently in the process of updating, their interconnection rules to address the unique characteristics of storage. However, a great deal of work remains, not just in the number of states that still have to integrate storage into their interconnection rules, but in developing solutions to the complex technical and procedural challenges of storage interconnection.

In response to the need for solutions, the Building a Technically Reliable Interconnection Evolution for Storage (BATRIES) project provides recommendations and best practices for eight critical storage interconnection challenges. The BATRIES project team selected the barriers to address through a stakeholder engagement process that included the input of utilities, DER developers, public service commission regulatory staff, smart inverter manufacturers, and others. The partners also drew upon their experience engaging in research on storage interconnection and participating in related state regulatory proceedings.

The storage interconnection barriers addressed in the Toolkit and Guidance for the Interconnection of Energy Storage and Solar-Plus-Storage (Toolkit) include:

• Lack of inclusion of storage in interconnection rules, and the lack of clarity as to whether and how existing interconnection rules (and related documents, such as application forms and agreements) apply to storage systems (addressed in Chapter II)
• Lack of inclusion of acceptable methods that can be used for controlling export of limited-and non-export systems in interconnection rules (addressed in Chapter III)
• Evaluation of non- and limited-export systems based on unrealistic operating assumptions that lead to overestimated grid impacts (addressed in Chapter IV)
• Lack of clarity regarding the impacts of inadvertent export from limited- and non-export systems and the lack of a uniform specification for export control equipment response times to address inadvertent export (addressed in Chapter V)
• Lack of information about the distribution grid and its constraints that can inform where and how to interconnect storage (addressed in Chapter VI)
• Lack of ability to make system design changes to address grid impacts and avoid upgrades during the interconnection review process (addressed in Chapter VII)
• States that have not incorporated updated standards into their interconnection procedures and technical requirements (addressed in Chapter VIII)
• Lack of defined rules and processes for the evaluation of operating schedules (Chapter IX)

Click on a chapter above to read the key takeaways and download the chapter file. Or download the full Toolkit and Guidance for the Interconnection of Energy Storage and Solar-Plus-Storage for all chapters and recommendations.

BATRIES is led by the Interstate Renewable Energy Council (IREC), in collaboration with a team of partners^[1]Note: The Energy Storage Association (ESA) was a partner on the BATRIES project through December 2021, before merging with the American Clean Power Association (ACP) in January 2022. ACP is not a … Continue reading—collectively, the Storage Interconnection Committee (STORIC)—which includes:

1. Electric Power Research Institute
2. Solar Energy Industries Association
3. California Solar & Storage Association
4. New Hampshire Electric Cooperative, Inc.
5. PacifiCorp
6. Shute, Mihaly & Weinberger, LLP

The BATRIES project team looks forward to continuing to engage with stakeholders to implement the solutions recommended in this Toolkit.