Renewable Energy System Interconnection Standards
NREL provides information and resources to U.S. states and communities on interconnection standards—how renewable energy systems can be legally connected to the electricity grid.
Interconnection standards are a set of requirements and procedures for both utilities and customers. Typically, they outline a multistep process. In some jurisdictions, simple systems (e.g., smaller and inverter-based) can be eligible for simplified, or fast-tracked, interconnection approval processes. For more complex systems, or in jurisdictions where simplified interconnection is not available, interconnection is generally a multistage process.
While interconnection standards are usually implemented at the state regulatory level and mandate how utilities must connect renewable energy systems to the electric grid, there is often a parallel permitting process required by a local jurisdiction (e.g., municipal building permit department) to ensure that residents' systems are installed safely by installers, contractors, or the residents themselves.
In the United States, state-level public utility commissions (PUCs) establish interconnection standards that customers and utilities must follow. Standards vary by state. Additionally, in May 2005, the Federal Energy Regulatory Commission (FERC) enacted interconnection standards for projects up to 20 MW for projects subject to FERC's jurisdiction. These are called the Small Generator Interconnection Procedures.
Most states do not regulate cooperatives and municipal electric companies.
Interconnection standards establish transparent processes for multiple stakeholders to follow ensuring safe deployment of renewable energy systems. Transparency also provides more certainty and less risk for renewable energy system investors and developers.
Unclear, lengthy, and complicated interconnection standards may increase distributed generation “soft costs” (i.e., nonhardware costs), thereby delaying the deployment of renewable energy systems. Although most states have net energy metering policies, some have not followed through with interconnection policy or rulemaking and have deferred responsibility to utilities.
Design Best Practices To Support Distributed Generation
Although interconnection standards are not consistent across states and utilities, many states adopt engineering and safety requirements based on IEEE 1547 and UL 1741 standards. Additionally, state interconnection standards are increasingly modeled after FERC's Small Generator Interconnection Procedures. Interconnection standards can also vary by:
- Net-metered versus non-net-metered systems
- System capacity requirements
- Eligible technologies
- Eligible sectors (e.g., commercial, residential)
- Insurance requirements.
A Guide to Updating Interconnection Rules and Incorporating IEEE Std 1547-2018, NREL Technical Report (2021)
A Guide to Updating Interconnection Rules and Incorporating IEEE Std 1547-2018, NREL Technical Report (2018)
A State-Level Comparison of Processes and Timelines for Distributed Photovoltaic Interconnection in the United States, NREL Technical Report (2015)
On the Path to SunShot: Emerging Issues and Challenges in Integrating Solar With the Distribution System, NREL Technical Report (2016)
Updating Distributed Energy Resource Interconnection Rules, NREL Technical Report (2022)
i2X: The Interconnection Innovation e-Xchange, U.S. Department of Energy
Decision Options Matrix for IEEE 1547-2018 Adoption, IREC (2018)Freeing the Grid: Interconnection, VoteSolar.org