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Interconnection standards specify the technical, legal and procedural requirements that customers and utilities must abide by when a customer seeks to connect a renewable-energy system to the grid. In states without comprehensive interconnection standards in place, it is often more difficult, more burdensome and more expensive for customers to connect a system to the grid. In general, states may regulate the interconnection of electricity-generating systems to distribution systems, while the Federal Energy Regulatory Commission (FERC) regulates the interconnection of systems to transmission lines.
Some states have adopted comprehensive interconnection standards that apply to all types and sizes of customer-sited systems, regardless of whether the system is net-metered. Some states have adopted interconnection standards that apply only to smaller systems that are net-metered. Some states have adopted interconnection guidelines that are vague and do not constitute standards. Other states have not adopted interconnection standards or guidelines. Comprehensive interconnection standards are developed by state public utility commissions, often when commissions directed to do so by state legislatures.
The technical issues related to interconnection are addressed by the IEEE 1547 Standard for Interconnecting Distributed Resources with Electric Power Systems. All states with comprehensive interconnection standards require compliance with the IEEE 1547 technical standard. However, the policy issues related to interconnection are more complex and vary by state. While some states’ interconnection standards apply to customers of all types of utilities (e.g., investor-owned utilities, municipal utilities and electric cooperatives), others apply only to customers of investor-owned utilities. In addition, state interconnection standards vary widely by several other key criteria, including individual system capacity limit, interconnection fees, use of a standard form agreement, insurance requirements, use of an external disconnect switch, and provisions for interconnection to area networks (i.e., complex grids that serve highly urban areas). The "Freeing the Grid" project provides a detailed breakdown of the individual components of each state's policy and an overall letter grade describing the overall quality of each, based on current best practices.
Status & Trends
States have become fully aware that comprehensive interconnection standards are a critical component of the development of in-state renewables markets. More than 30 states plus D.C. and Puerto Rico have adopted comprehensive interconnection standards that apply to customer-sited systems (both large and small), regardless of whether the system is net-metered. Around 10 other states, including Arkansas and Georgia, have adopted standards or guidelines that only apply to smaller, net-metered systems.
Most states with comprehensive standards have established multiple levels of review based on system capacity, complexity and level of certification. In these states, applications for small, certified systems are processed quickly, while larger systems and uncertified systems require closer review. By establishing multiple levels of review, states ensure that the owner of a five-kilowatt photovoltaic (PV) system may interconnect quickly, safely and inexpensively, without having to endure a process more suitable to a 10-megawatt combined heat and power (CHP) system. Some states have moved toward developing separate interconnection requirements for net-metered systems and non-net metered systems. Notably, some states have determined that larger systems that do not export electricity should require a less rigorous review process than larger systems that do export electricity.
With respect to smaller PV systems and certain other systems, public utilities commissions in several states, such as Maine, Oregon and North Carolina, have concluded that an external disconnect switch is not necessary and have prohibited utilities from requiring customers to install such a switch. (Several larger electric utilities, including PG&E and SMUD, have voluntarily reached the same conclusion and abandoned previous requirements for an external disconnect switch for smaller PV systems.) Similarly, public utilities commissions generally do not require customers to purchase liability insurance beyond the amount included in a typical homeowner’s policy or business owner’s policy.
The Interstate Renewable Energy Council, Inc. (IREC) has established the following best practices for state interconnection standards:
Freeing the Grid. Vote Solar, et al., 2013.
Updating Small Generator Interconnection Procedures. Keyes, Fox & Wiedman LLP, 2012.
Model Interconnection Standards. Interstate Renewable Energy Council, Inc. (IREC), 2009.
Connecting to the Grid: A Guide to Distributed Generation Interconnection Issues. Laurel Varnado and Mike Sheehan. Interstate Renewable Energy Council, Inc. (IREC), 6th Edition, October 2009.
Utility-Interconnected Photovoltaic Systems: Evaluating the Rationale for the Utility-Accessible External Disconnect Switch. National Renewable Energy Laboratory (NREL), January 2008.
IEEE 1547 Standard for Interconnecting Distributed Resources with Electric Power Systems. IEEE, 2004.
 Freeing the Grid 2011, Network for New Energy Choices, et al., October 2011.
Disclaimer: The information presented on the DSIRE web site provides an unofficial overview of financial incentives and other policies. It does not constitute professional tax advice or other professional financial guidance, and it should not be used as the only source of information when making purchasing decisions, investment decisions or tax decisions, or when executing other binding agreements. Please refer to the individual contact provided below each summary to verify that a specific financial incentive or other policy applies to your project.
While the DSIRE staff strives to provide the best information possible, the DSIRE staff, the N.C. Solar Center, N.C. State University and the Interstate Renewable Energy Council, Inc. make no representations or warranties, either express or implied, concerning the accuracy, completeness, reliability or suitability of the information. The DSIRE staff, the N.C. Solar Center, N.C. State University and the Interstate Renewable Energy Council, Inc. disclaim all liability of any kind arising out of your use or misuse of the information contained or referenced on DSIRE Web pages.