Solar, Storage, Wind Drive 95% of US Interconnection Queues as Backlog Rises

Low completion rates of projects are increasing wait times


Nearly 12,000 power projects, an overwhelming majority based on renewable sources, representing a combined capacity of 1,570 GW and 1,030 GW for storage, are in interconnection queues in the U.S.

Renewable sources constitute 95% of the total capacity in the active queue. Over 94% or about 1,480 GW of the proposed generation capacity is zero-carbon, according to a recent Berkeley Lab report.

Utilities and regional grid operators mandate that projects wishing to link to the grid must undergo a sequence of assessments before construction. This procedure determines the potential necessity for new grid system enhancements before a project can integrate into the system, estimating and allocating the associated equipment costs.

The rosters of projects applying for grid connection and initiating this evaluation process are called “interconnection queues.”

While developer interest in solar, storage, and wind energy remains robust, completion rates for these projects are generally low, leading to increasing wait times. Only about 19% of projects (equivalent to 14% of total capacity) that requested interconnection between 2000 and 2018 reached commercial operations by the end of 2023.

Completion rates are notably lower for solar (14%) and battery (11%) projects.

Wait times rise

The average time projects spend in the queue before becoming operational has significantly risen. In 2023, an average project took nearly five years from the interconnection request to commercial operations, compared to three years in 2015 and less than two years in 2008.

The proposed capacity is widely dispersed across the U.S. Solar capacity is proposed in most regions, with over 1 TW of solar actively queued.

Additionally, there is over 1 TW of storage capacity in the queues, primarily concentrated in the Western region and California Independent System Operator (CAISO), but also present in the Electric Reliability Council of Texas (ERCOT), Midcontinent Independent System Operator (MISOM), and Pennsylvania-Jersey-Maryland Interconnection (PJM). Wind capacity accounts for over 360 GW in the queues, with the majority located in the non-ISO West, New York Independent System Operator (NYISO) (offshore), PJM, and Southwest Power Pool (SPP) regions.

Solar (1,086 GW), storage (1,028 GW), and wind (366 GW) collectively represent 95% of the total active capacity in the queues. Most of the solar and storage capacity is part of hybrid power projects.

Since the enactment of the Infrastructure and Reconciliation Act (IRA), over 1,200 GW of capacity (including more than 500 GW of solar, over 540 GW of storage, and 125 GW of wind) have applied for interconnection.

The IRA has introduced a suite of tax credits and other measures to accelerate clean energy development.

While not all the interconnection requests made after the IRA can be directly attributed to its provisions, these measures have significantly increased developer interest in clean energy.

Nearly 99% of the storage capacity in the interconnection queues is battery-based. However, active requests total 10 GW for pumped hydro, hydrogen, and compressed air energy storage.

The U.S. Federal Energy Regulatory Commission outlined steps to cut down the long queues of renewable energy projects awaiting interconnection to the nation’s transmission grid.

Interconnection agreements

About 49% (1,271 GW) of the total capacity in the interconnection queues has proposed online dates by the end of 2026. Currently, 12% (311 GW) of this capacity already have executed interconnection agreements.

Approximately 52% of solar capacity (566 GW) is projected to be operational by the end of 2026, compared to 50% of storage capacity (514 GW) and only 33% of wind capacity (120 GW). Moreover, 14% of solar capacity has IAs, 15% of wind, and 10% of storage.

There is a noticeable increase in capacity within hybrid plants, with hybrids constituting 53% of active solar capacity (571 GW), 51% of storage capacity (525 GW), and 13% of wind capacity (49 GW).

Hybrid power project capacities including solar energy make up – solar+storage (548 GW), solar+wind (0.2 GW), and solar+wind+storage (12 GW). Wind power included hybrid projects cover wind+storage (35 GW), wind+solar (0.2 GW), and wind+solar+storage (13 GW).

Over 70% of interconnection requests are ultimately withdrawn. Only a small fraction, around 19% of requests (equivalent to 14% of the total capacity) submitted between 2000 and 2018, had been completed and built as of the end of 2023.

Study timelines

Wind projects generally experience longer interconnection study timelines than recent battery and gas projects.

Wind projects typically also require a longer duration to progress from the request date to commercial operations compared to other types, with standalone battery projects exhibiting the fastest progression.

As of the end of 2023, the combined capacity of just solar and wind now active in the queues exceeds the total installed U.S. power project fleet capacity and surpasses the estimated capacity needed to approach a zero-carbon electricity target.

Hybrids, particularly solar (solar+battery) and wind hybrids, comprise a significant and growing share of proposed projects, especially in the CAISO and Western regions.

Approximately half of the active capacity in the queues is projected to come online before 2026, with 12% already having executed interconnection agreements.