Model procedures for fixing distributed solar and storage interconnection


Interconnection processes for distributed solar and storage across the 50 states have much room for improvement, as the Interstate Renewable Energy Council (IREC) and Vote Solar highlighted in their report “Freeing the Grid,” which graded each state’s process, as shown in the image above.

To help states achieve faster, lower-cost interconnection of distributed energy resources (DERs), IREC has published model interconnection procedures that any state could adopt to upgrade its DER interconnection process.

The procedures are based on best practices already in use nationwide, IREC says in an introduction to the document, and are intended to “save money and time for consumers, developers and utilities alike.”

The model procedures “can serve different functions depending on what is needed for a state,” said Gwendolyn Brown, IREC’s vice president of communications. “They can be adopted word-for-word or with modest changes; they can be used as a starting point for discussions and modified more or less, depending on the state’s needs; or specific provisions can be pulled from the model procedures and inserted into existing state rules.”

If the model procedures themselves were scored against the “Freeing the Grid” criteria, “they would get an A,” Brown said.

IEEE 1547-2018

The model procedures advise that any current state rules and utility interconnection procedures that are based on the IEEE Standard 1547-2003 “will need to be updated” to reflect the new IEEE Standard 1547-2018, which “will transform how DERs interact with and function on” the grid.

The new IEEE standard requires DERs to be capable of providing specific grid-supportive functionalities relating to voltage, frequency, communications, and controls, says IREC’s document. The voltage functionalities for DERs meeting the new IEEE standard are known as volt-var and volt-watt.

Once the IEEE-1547 functions are widely utilized, they “will enable higher penetration of DERs on the grid, while maintaining grid safety and reliability and providing new grid and consumer benefits,” IREC says. IREC promotes the use of voltage regulation functions “sooner rather than later” to avoid a high volume of DERs that do not provide such capabilities, Brown said.

In Hawaii, distributed solar has reached a substantial percentage of generation largely through the use of the volt-var setting for all new installations; Hawaii also allows enabling the volt-watt setting for customers who choose it. California uses the volt-var and volt-watt settings in all cases, although the volt-watt decision involved a controversy over consumer protection, IREC has reported.


IREC said that “many states’ interconnection procedures have been updated to ensure efficient interconnection of energy storage,” and given that experience base, the model procedures now include “important updates” for interconnecting solar-plus-storage and standalone storage. Those updates emerged from an IREC-led project to advance the use of distributed batteries through publication of a “BATRIES Toolkit” last year.

IREC also flagged four other categories of important updates in the model procedures, compared to IREC’s previous model procedures published in 2019.


IREC acknowledged that the “existing best practices” captured in the model procedures do not always reflect innovations that have not yet been “sufficiently deployed and tested.” For example, the model procedures “do not yet fully incorporate the use of hosting capacity analyses,” IREC says, “although IREC strongly recommends states begin adopting robust hosting capacity analyses.”

Also, as some states have developed group study processes “to increase study efficiency and more fairly allocate upgrade costs,” IREC said it plans to analyze group study practices and potential challenges in a paper it expects to publish this fall.


IREC’s model procedures are titled “Model Interconnection Procedures: 2023 Edition.”

IREC will host a webinar on September 7 to discuss the model procedures.

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