I. Introduction

Energy storage systems (storage or ESS) are crucial to enabling the transition to a clean energy economy and a low-carbon grid. Storage is unique from other types of distributed energy resources (DERs) in several respects that present both challenges and opportunities in how storage systems are interconnected and operated. Although many jurisdictions are taking steps toward integrating storage, substantial technical and regulatory barriers remain to the rapid integration of ESS onto the grid, including and especially related to interconnection.

Well-designed interconnection rules that effectively address the unique operating capabilities and benefits of storage are essential to the rapid and cost-efficient integration of storage onto the grid in a safe and reliable manner. The Building a Technically Reliable Interconnection Evolution for Storage (BATRIES) project provides recommended solutions and resources for eight critical storage interconnection barriers, to enable safer, more cost-effective, and efficient grid integration of storage in this Toolkit and Guidance for the Interconnection of Energy Storage and Solar-Plus-Storage (Toolkit).

A growing number of states have adopted ambitious climate and clean energy mandates, from renewable generation and electrification targets to greenhouse gas reduction goals.^[1]See, e.g., National Conference of State Legislatures, State Renewable Portfolio Standards and Goals (last accessed November 15, 2021), … Continue reading At the same time, residential, commercial, and industrial customers^[2]For ease of reference, this document sometimes uses the broad term “interconnection customers.” are investing in storage for the economic and environmental benefits it provides.^[3]U.S. Energy Information Administration, Battery Storage in the United States: An Update on Market Trends (Aug. 2021), … Continue reading

As renewable energy deployment grows both in front of and behind the meter, individual customers and electric distribution system operators are likely to increasingly rely on storage for the energy management services it provides. For example, storage paired with solar can enable managed import and export. This can have benefits for both the customer and the grid. Better timing of the use of distributed resources can minimize the cost of solar interconnection by reducing the need for grid upgrades.^[4]See, e.g., Thomas Bowen and Carishma Gokhale-Welch, Behind-the-Meter Battery Energy Storage: Frequently Asked Questions, National Renewable Energy Laboratory (Aug. 2021), pp. 2-4, … Continue reading Utility-scale storage can support resource management in states with high wind and solar penetration by mitigating the intermittency of renewable generation.^[5]Id. New federal policies are also likely to incentivize the increased adoption of storage, particularly through the Federal Energy Regulatory Commission (FERC) Order 2222, which is intended to pave the way for aggregated DERs—including storage—on the distribution system to compete in wholesale markets.^[6]Federal Energy Regulatory Commission, Docket No. RM18-9-000, Order No. 2222, Participation of Distributed Energy Resource Aggregations in Markets Operated by Regional Transmission Organizations and … Continue reading

Storage differs from other types of DERs, such as solar and wind generation, in several key aspects that shape the way it is interconnected to, and operated on, the grid. For example, storage can serve as both generation and load, either discharging to or charging from the grid or a paired solar system or other generation source. In addition, storage systems can be designed to control when and how much they export to, or import from, the grid, and thus can provide cost and energy management benefits to customers and the grid. These operating capabilities make storage a valuable asset, and also introduce complexities in the interconnection process as regulators must strike a balance between maximizing the energy and economic benefits of storage from a customer perspective, and the need to maintain safe and reliable service from a utility perspective.

In addition, storage has an important role to play in enabling states to achieve their climate and energy goals and more efficient operation of the grid. Behind-the-meter storage can increase resilience and reduce energy costs for customers; allow utilities to defer infrastructure investments necessary to serve peak demand; and support the integration of more renewable energy resources, such as by providing frequency regulation and mitigating the variable output of renewables.^[7]International Renewable Energy Agency, Behind-the-Meter Batteries: Innovation Landscape Brief (2019), pp. 10-13, … Continue reading

In response, several states have updated, or are currently in the process of updating, their DER interconnection rules to include storage and to enable its more time- and cost-efficient integration onto the grid, which is critical for scaling storage deployment. To date, Arizona, California, Colorado, the District of Columbia, Hawaii, Maryland, Minnesota, Nevada, New York, North Carolina, and Virginia have DER interconnection rules that facilitate the interconnection of ESS.^[8]AZ Administrative Code § R14-2 (Feb. 25, 2020); CA Pub. Util. Comm., Southern California Edison, Rule 21; DC Mun. Regs. tit. 15, chapter 40 (Jan. 25, 2019); HI Pub. Util. Comm., Rules 22-24 (Feb. … Continue reading As of December 2021, Illinois, Massachusetts, Maine, and New Mexico are in the process of revising their interconnection rules to facilitate the interconnection of ESS.^[9]CO Pub. Util. Comm., Dkt. 21I-0321E, Investigation Into the Interconnection of Distributed Energy Resources (July 12, 2021); IL Com. Comm, Dkt. 10-0700. Second Notice Order(Aug. 12, 2021) (proposing … Continue reading

Interconnection procedures serve as the “rules of the road” for DER integration onto the electric grid. They include rules relating to the process, cost, and timeline for interconnection, and can include related documents, such as template forms and applications. The procedures for distribution grids are typically spelled out in rules or tariffs approved by state public utility commissions (PUCs). In developing their interconnection procedures, many states have relied on one of two model rules: the Federal Energy Regulatory Commission’s (FERC) Small Generator Interconnection Procedures (SGIP), and the Interstate Renewable Energy Council’s (IREC) Model Interconnection Procedures (IREC 2019 Model). In addition to these resources, state interconnection procedures may also reference technical interconnection standards, including, but not limited to the Institute of Electric and Electronic Engineers’ 1547-2018 standard (IEEE 1547-2018^TM), IEEE Standard for Interconnection and Interoperability of Distributed Energy Resources with Associated Electric Power System Interfaces.

The design of interconnection procedures can have a significant impact on the efficiency and cost-effectiveness of DER integration, including project viability.^[10]See, e.g., Ivan Penn, Old Power Gear Is Slowing Use of Clean Energy and Electric Cars, New York Times (Oct. 8, 2021), … Continue reading Interconnection procedures that are not tailored to the jurisdiction’s DER market conditions—such as when the speed of DER deployment outstrips the ability of utilities to keep pace with processing applications or the ability of the grid to accommodate higher penetrations of DERs—can result in significant queue backlogs or grid upgrade fees that are too high for the market to bear. On the other hand, interconnection procedures that are designed to successfully meet the demands of the DER market can facilitate the more rapid and efficient integration of DERs.

While a number of states have taken initial steps to ease the path for storage interconnection, the majority of PUCs and utilities have yet to reform their interconnection rules to be inclusive of storage. The process of revising interconnection rules and tariffs is, more often than not, lengthy and resource-intensive, and requires a high level of procedural and technical expertise. The challenge is compounded by the fact that technical standards applicable to storage continue to evolve, and many of the solutions to ease storage interconnection involve cutting-edge practices and procedures that have not yet been widely adopted. In short, there is a pressing need for guidance and implementable resources on storage interconnection that regulators, utilities, and other stakeholders can use to update their respective state interconnection procedures.

The BATRIES project helps to explain the challenges and presents solutions to several key technical and regulatory barriers to the interconnection of storage on the distribution system.^[11]The BATRIES project is focused on distribution-interconnected storage, whether ESS is interconnected in front of or behind the meter, and irrespective of system size. BATRIES does not address … Continue reading BATRIES is a three-year effort funded by the U.S. Department of Energy’s Solar Energy Technologies Office. It brings together stakeholders from all relevant interest groups, including storage and DER developers, utilities, state regulatory commissions and staff, national research laboratories, and storage technology manufacturers to identify the critical challenges to ESS interconnection and present effective solutions as part of this Toolkit and Guidance for the Interconnection of Energy Storage and Solar-Plus-Storage (Toolkit).

BATRIES is led by the Interstate Renewable Energy Council (IREC), in collaboration with a team of partners—collectively, the Storage Interconnection Committee (STORIC), which includes:^[12]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

• Electric Power Research Institute (EPRI)
• Solar Energy Industries Association (SEIA)
• California Solar & Storage Association (CALSSA)
• New Hampshire Electric Cooperative, Inc. (NHEC)
• PacifiCorp
• Shute, Mihaly & Weinberger, LLP

Working collaboratively, and with input from external stakeholders representing PUC regulatory staff, utilities, developers, and DER associations, ^[13]STORIC hosted two half-day workshops and made several presentations to gather input from stakeholders, and solicited peer review from subject matter experts of the proposed barriers to include in the … Continue reading STORIC developed an initial list of nearly forty storage interconnection challenges that encompasses technical, financing, and procedural issues. To develop a prioritized list of barriers that the BATRIES project could address within the project resources and timeframe, STORIC undertook a screening process that evaluated the initial set of barriers through several lenses, including whether other stakeholders are already working toward developing solutions on the issues; whether solutions would result in reduced costs and time for storage interconnection in furtherance of the project’s objectives; and whether the issues represent a timely challenge that regulators, utilities, and developers are currently facing (as compared to a theoretical barrier that could pose a challenge in the more distant future).

As a result, STORIC identified the following eight priority storage interconnection barriers, which are included in the Toolkit:

• Updating Interconnection Procedures to Be Inclusive of Storage (Chapter II)
• Requirements for Limited- and Non-Export Controls (Chapter III)
• Evaluation of Non-Export and Limited-Export Systems During the Screening or Study Process (Chapter IV)
• Defining How to Address Inadvertent Export (Chapter V)
• Improving Grid Transparency Through Hosting Capacity Analyses and Other Tools (Chapter VI)
• Pathways to Allow for System Design Changes During the Interconnection Review Processes to Mitigate the Need for Upgrades (Chapter VII)
• Incorporating Updated Interconnection Standards Into Interconnection Procedures (Chapter VIII)
• Defining Rules and Processes for the Evaluation of Operating Schedules (Chapter IX)

The above eight barriers were selected based upon the collective experience of STORIC members who have engaged on these issues within regulatory proceedings and research and development contexts, and with input from external subject matter experts based on their own on-the-ground experience. The barriers are all at play within regulatory proceedings across the U.S., as further described in the Toolkit chapters below, highlighting the need for guidance and resources for regulators, developers, and utilities.

There are many more storage interconnection challenges than the BATRIES project could address within the project timeframe and resources.^[14]For example, based on the scoping work described above, the project team identified interconnection challenges associated with non- and limited-export as being high priority. As such, while there can … Continue reading To facilitate the future development of solutions related to barriers not included in BATRIES, the project team provides a list of the unaddressed barriers in Appendix A for consideration by other stakeholders.

The recommendations included in the Toolkit are focused on storage interconnected to radial distribution systems,^[15]Some recommendations may also apply to networked distribution systems. However, due to the technical differences between radial and networked systems, and the fact that radial systems prevail in the … Continue reading whether ESS is interconnected in front of or behind the meter, and generally irrespective of system size (though the chapters below note instances in which specific discussions or recommendations have more limited applicability). Recommendations are designed for use in interconnection procedures for the distribution system. Nationally, interconnection standards are quite consistent structurally, with most following the structures of either the FERC’s SGIP or IREC’s Model Interconnection Procedures. These two models utilize a largely parallel structure and have similar interconnection screens and technical requirements. In order to develop model language for interconnection standards that can be adopted by states across the country, BATRIES generally uses the language from FERC SGIP to illustrate recommended revisions.^[16]Note that BATRIES is not focused on recommending revisions to SGIP itself; rather it uses SGIP as a common reference point for model language that could be folded into individual states’ … Continue reading These recommendations should be easy to translate to other rules that utilize different formats.

Energy storage is a critical piece of the clean energy puzzle and solutions for enabling the more rapid and efficient integration of storage will continue to develop. The BATRIES project team looks forward to continuing dialogue with stakeholders on the storage interconnection barriers included in the Toolkit as well as the evolving universe of other storage interconnection challenges and opportunities.

Toolkit Quick Reference Guide Chapter II – Updating Interconnection Procedures to Be Inclusive of Storage Provides recommendations on how to ensure interconnection rules apply to ESS and recommends definitions for key terms that will be needed for ESS interconnection review. Chapter III – Requirements for Limited- and Non-Export Controls Includes recommendations for ensuring acceptable export control in interconnection procedures that maintain safety and reliability. Chapter IV – Evaluation of Non-Export and Limited-Export Systems During the Screening or Study Process Offers recommendations on how interconnection screening and study processes can be updated to recognize export controls. Chapter V – Defining How to Address Inadvertent Export Surveys how current standards treat inadvertent export and details the results of research conducted to test its potential grid impacts. Chapter VI – Improving Grid Transparency Through Hosting Capacity Analyses and Other Tools Discusses how grid transparency tools, such as pre-application reports and hosting capacity maps, can help improve interconnection of DERs by assisting with good site selection and project design. Chapter VII – Pathways to Allow for System Design Changes During the Interconnection Review Process to Mitigate the Need for Upgrades Includes recommendations on how rule language can be revised to accommodate ESS project modifications during the interconnection process. Chapter VIII – Incorporating Updated Interconnection Standards Into Interconnection Procedures Provides recommendations on how to incorporate technical standards, such as the suite of IEEE 1547 standards, into interconnection procedures. Chapter IX – Defining Rules and Processes for the Evaluation of Operating Schedules Discusses what steps need to be taken to allow devices to reliably control import and export according to a schedule.

How To Use the Toolkit to Address Challenges

The Toolkit is meant to assist state regulators, utilities, and other stakeholders in addressing interconnection barriers related to the above topics. The recommendations and model language provided in the Toolkit can be used in regulatory proceedings and working groups to update interconnection procedures and practices to account for ESS and its unique capabilities on the grid. In its recommended model language revisions, the Toolkit uses FERC SGIP as a starting point (and provides model language for related forms, such as interconnection application forms that customers may complete in online portals), but states should easily be able to incorporate any changes into their own interconnection rules—whether they are based on FERC SGIP, IREC’s 2019 Model Rules, or any other model language.

Recommended model language is presented in italics. Entirely new model language (i.e., not revisions to existing text) is presented only in italics. Revisions to existing model language are presented in strikethrough (for deletions) and double underline (for additions).

Note that terms and definitions are sometimes repeated throughout chapters of the Toolkit for readers who may wish to read a particular chapter without reviewing the prior chapters.

Considerations for States or Utilities Experiencing Lower Energy Storage Market Penetration or With More Limited Resources for DER-Related Investments

The solutions provided in the Toolkit are intended to have broad applicability, but some may be less applicable in jurisdictions that have limited storage market penetration (or prospects for near-term market growth), or for utilities with fewer resources to invest in the staffing, information technology, or other tools necessary for deploying the solutions (e.g., smaller municipal or cooperative utilities). In such instances, regulators and utilities can prioritize the Toolkit solutions as follows:

• Start by reviewing Chapters II, III, and IV to understand how to enable the full capabilities of ESS and how to screen for inadvertent export impacts. (Chapter V provides more information on inadvertent export.)
• Pursuant to Chapter VI, consider whether any of the recommended grid transparency tools align with both the needs of interconnection applicants and the utility’s resources and capabilities. Review Chapter VIII to understand how updated technical standards can enable additional ESS functionalities and maximize the benefits to both customers and grid operators.

Download the chapter file below to read more. Or download the full Toolkit and Guidance for the Interconnection of Energy Storage and Solar-Plus-Storage for all chapters and recommendations.