Thinking Outside the Lines: Group Studies in the Distribution Interconnection Process

This report, Thinking Outside the Lines: Group Studies in the Distribution Interconnection Process, provides guidance on the use of “group studies,” an emerging practice to streamline the interconnection of distributed energy resources (DERs)—such as solar PV, community solar, and energy storage—to the electric distribution grid. 

The report aims to help regulators, utilities, and clean energy stakeholders evaluate whether group studies may be an effective avenue for addressing interconnection issues in their jurisdictions. This is an important and timely question because, as an increasing number of DER projects seek to interconnect to the grid, the interconnection process has slowed in many states. It is not uncommon for DER projects to spend years waiting in a queue to be studied.

The standard practice over the last 20 years has been to study DER projects one at a time, in the order in which they requested to interconnect, to determine if each can safely interconnect to the distribution system and if any grid upgrades will be needed. This process of studying projects one by one can contribute to projects piling up in the queue as they await their turn to be studied. In contrast, a “group study” evaluates in a single study whether a group of multiple electrically-related DER projects can safely interconnect and identifies any grid upgrades that are needed to accommodate the group. Unlike individual studies, projects in the same group typically share the costs of the study and any common distribution or network upgrades. While common at the transmission level, group studies have only recently been widely considered at the distribution level.

The report evaluates different group study approaches currently in use and how well they function. It examines five case studies from jurisdictions that have adopted group study processes (California, Massachusetts, Minnesota, Oregon, and North Carolina). The report draws upon IREC’s participation in multiple public utility regulatory proceedings on the formation of group study processes, as well as substantial original research, including interviews with interconnection customers, utilities, and regulatory staff.