PJM interconnection queue: questions developers, analysts, and site selectors ask

The PJM interconnection queue is the ordered list of generation projects that have requested permission to connect to the PJM transmission grid. Projects move through three formal study phases — Feasibility Study, System Impact Study, and Facilities Study — before they can sign a Generator Interconnection Agreement (GIA) and proceed to construction. The full process takes multiple years. PJM publishes the active queue and many of the resulting study reports on its public website.

Multiple years end-to-end. Lawrence Berkeley National Laboratory's "Queued Up" research found that a typical U.S. interconnection project took nearly five years from application to completion in 2023, up from about three years in 2015. PJM's own cluster study reforms (in response to FERC Order 2023) are intended to reduce that timeline, but the backlog remains substantial. Actual time depends on the project's study phase, cluster timing, and any required network upgrades.

Across all technologies, the historical withdrawal rate from U.S. interconnection queues is roughly 80%. Berkeley Lab's research on projects that entered queues between 2000 and 2018 found build rates of approximately 14% for solar, 11% for storage, and around 32% for natural gas. These figures vary by ISO and by cohort year, and they do not predict the outcome for any specific project. They do, however, suggest that the raw queue MW visible in any ISO database significantly overstates the capacity that will realistically compete for headroom at any given substation.

Queue attrition is the phenomenon where most projects in interconnection queues never get built. Because the queue is publicly listed but withdrawal rates are high, the apparent "competitive load" at any given Point of Interconnection (POI) is significantly inflated. Anyone evaluating a candidate POI who looks only at raw queue MW will overestimate how much capacity is actually competing for headroom. Anticipating which queued projects will withdraw is a major source of uncertainty — and competitive advantage — in site selection and interconnection strategy.

A Facilities Study Report is the third and final formal study in PJM's interconnection process, issued before the Generator Interconnection Agreement (GIA) is executed. It documents the specific network upgrades required to connect a project, an itemized cost estimate (typically with both Transmission Owner-Build and Developer-Build options), a milestone schedule, and any dependencies on neighboring projects in the queue. PJM posts these reports publicly per project. SlackWatt has parsed a sample of these reports to extract cost and dependency data for use in its prototype queue analysis tools.

A Point of Interconnection (POI) is the specific physical point — usually a transmission substation — where a generation project connects to the grid. POI selection is one of the most consequential early decisions a developer makes, because it determines which neighboring queued projects compete for headroom, which network upgrades are likely to be required, and which Transmission Owner the project will deal with.

ERIS (Energy Resource Interconnection Service) is the lower-cost option: the project can deliver energy when transmission capacity is available, but receives no firm guarantee of network delivery during peak conditions. NRIS (Network Resource Interconnection Service) is the higher-cost option: the project receives full guarantees of network delivery and is eligible for full capacity recognition in PJM's capacity market. Most utility-scale projects targeting capacity revenue choose NRIS.

Hosting capacity is the maximum amount of new generation that can interconnect at a given location without causing reliability problems on the existing grid. ISOs and utilities publish hosting capacity maps and tools (PJM Queue Scope, SPP's Hosting Capacity Tool, MISO's Points of Interconnection tool) to give a starting view of where headroom exists today. These tools generally show current grid state, not projected state at the time a new project would energize.

PJM Queue Scope is a free public tool published by PJM that displays transmission availability (headroom) at user-defined Points of Interconnection across the PJM transmission system. The public tier requires no login. Full features, including confidential transmission data, require CEII (Critical Energy Infrastructure Information) clearance. Queue Scope's results reflect a snapshot in time and explicitly do not replace official PJM interconnection studies.

Several categories of tools exist. PJM's own Queue Scope is free and shows current headroom. Commercial platforms include Nira (queue attrition simulation and injection capacity studies), Enverus PRISM (a broader power and renewables data platform), and Pearl Street Technologies' Interconnect (scenario analysis with custom assumptions). Public data sources include PJM's queue download, Berkeley Lab's "Queued Up" dataset, and interconnection.fyi. SlackWatt's free Queue Reality Check prototype is a lightweight tool for toggling build/withdraw assumptions at a candidate POI without requiring a commercial subscription.

For the deep injection capacity analysis that Nira and Enverus PRISM provide, no — those are sophisticated paid platforms backed by significant engineering teams, and there is no free equivalent. For the narrower question of "how does my picture change if I assume specific queued projects withdraw," SlackWatt's Queue Reality Check prototype is free and requires no signup, but it covers PJM only and uses static seed data, not a live PJM feed. PJM Queue Scope is also free for the public data tier.

Common reasons include: network upgrade costs coming back higher than the project economics support; loss of land control or offtake agreements; financing falling through; permitting or environmental issues; and dependencies on other queued projects withdrawing or building. Because PJM Facilities Study cost estimates can swing significantly based on which neighboring queued projects build (a real example: project AF1-119's costs depend on whether project AF1-202 builds first), withdrawal decisions are often interlinked and can cascade.

Yes. Data center site selectors care about queued generation because the grid headroom and reliability at a candidate site depend on which queued generation projects build out and when. PJM in particular has seen a surge of large load interconnection requests driven by data center growth, and large loads are subject to their own interconnection processes that increasingly run alongside generator queues. The same queue attrition dynamics that affect generation developers shape the supply of power available to large industrial loads.

FERC Order 2023 is a 2023 federal rulemaking that mandates a sprawling set of interconnection process reforms across U.S. ISOs and RTOs. Major elements include moving from serial first-come-first-served studies to cluster studies, stricter "readiness" requirements (site control, permitting, financing) to weed out speculative projects, and tighter timelines for grid operators. Implementation varies across grid operators and is ongoing. The reforms are intended to reduce queue times and improve the build rate of projects that do interconnect, but the full effect will take years to materialize.

SlackWatt.com is an experimental free tool for anyone evaluating projects in the PJM interconnection queue — generator developers, load-side and data center site selectors, consultants, and analysts. The current tool, Queue Reality Check, is a prototype that lets users pick a POI, see nearby queued projects, and toggle build/withdraw assumptions to see how much capacity is realistically competing. SlackWatt is built by Lissjos Engineering LLC, a San Diego–based independent operations research and power systems consultancy.