The queues indicate particularly strong interest in solar, battery storage, and wind energy, which account for 95% of all proposed capacity. In fact, the combined solar and wind capacity now actively seeking grid interconnection (~1,250 GW) approximately equals the installed capacity of the entire U.S. power plant fleet.
But this growing backlog has become a major bottleneck for project development: projects are taking longer and longer to complete the interconnection study process and come online, and most of these interconnection requests are ultimately canceled and withdrawn. Entering an interconnection queue is only one of many steps in the development process; projects must also have agreements with landowners and communities, power purchasers, equipment suppliers, and financiers, and may face transmission upgrade requirements. Data from these queues nonetheless provide a general indicator for mid-term trends in developer interest.
Berkeley Lab compiled and analyzed data from the seven organized electricity markets in the US and additional 35 utilities outside of those regions, which collectively represent over 85% of all U.S. electricity load. The findings are reported in a new slide deck, data file, and interactive visualization that synthesize data from transmission interconnection queues throughout the United States to illustrate trends in proposed power plants across technologies, time, and regions.
“The interconnection queues illustrate both the opportunity and challenges of electric sector decarbonization in the US,” said Joseph Rand, an Energy Policy Researcher at Berkeley Lab, and lead author of the study. “On the one hand, we see unprecedented interest and investment in clean energy development. On the other hand, the increasing delays and high withdrawal rates point to a major barrier for developers of these projects.”
Rand points out that the amount of solar, wind, and storage in the queues today exceeds the amount needed to get to 90% of U.S. electricity from zero-carbon resources by 2035. President Biden has set ambitious goals to create a carbon pollution-free power sector by 2035 and net zero emissions economy by no later than 2050 to combat climate change. “The trends in these interconnection queues suggest that developers are eager to meet this ambition, though they may face some headwinds”, said Rand.
The grid of the future looks sunny and windy
The total capacity in the queue at the end of 2022, over 2 Terawatts (TW), is greater than current U.S. generating capacity of 1.25 TW, and more than six times larger than the queue in 2014. The passage of the Inflation Reduction Act – which increased incentives for renewable energy – is likely to drive even further growth in interconnection requests in coming years.
Solar (947 GW) accounts for the largest share of generation capacity in the queues, but substantial wind (300 GW) capacity has also applied for interconnection. The amount of offshore wind capacity in the queues (113 GW) represents more than three times the Biden Administration’s goal of 30 GW installed by 2030. Developer interest in electricity storage has exploded in recent years, with capacity in the queues reaching an estimated 670 GW as of the end of 2022.
Remarkably, the overall growth of capacity in the queues occurred despite major slow-downs in two of the largest grid operating regions: CAISO and PJM. Due to the massive influx of new interconnection requests in 2021, CAISO did not accept any new requests in 2022 as they process the backlog. PJM announced a pause on new interconnection reviews until at least 2025. Yet, these slowdowns were more than offset by enormous growth in other regions. Overall, proposed solar capacity exists in most regions of the US aside from the Northeast. Wind capacity is highest in New York (driven by offshore requests), the West, PJM, and SPP. Proposed storage is predominantly located in the West and CAISO, but is increasingly spreading to other regions. And only 82 GW of gas is active in the queues – less than 10% of active solar capacity.
Increasing interest in co-locating generation with storage
With falling battery prices and the growth of variable renewable generation, there has been a surge of interest in “hybrid” power plants that typically combine generating capacity with co-located batteries. At least 456 GW of solar capacity in the queues is proposed as a hybrid plant (48% of all solar in the queues), as is 24 GW of wind (8% of all wind in the queues). Over half of all storage capacity in the queues is proposed in hybrid configurations with generation (358 GW).
Interest in hybrid projects is especially strong in CAISO and the non-ISO West, where 97% and 81% of all proposed solar is in a hybrid configuration, respectively. “Pairing electric generation with co-located storage can add market value and flexibility, especially in regions with a lot of solar and wind like California,” said co-author Will Gorman, a Research Scientist at Berkeley Lab. The recent passing of the Inflation Reduction Act (IRA), however, boosted incentives for standalone storage, which could impact these trends in the future.
Backlogs, bottlenecks, and barriers: opportunities for improvement
But there is a big caveat: Much of the proposed capacity in the queues will not ultimately be built since projects may not come to fruition for a variety of reasons. Looking back at a subset of queues for which data are available, only 21% of the projects (and just 14% of capacity) seeking connection from 2000 to 2017 subsequently reached commercial operations (the final outcome of more recent projects cannot yet be determined). Concerningly, more recent projects seem to be waiting until later stages of the interconnection process to make the determination to cancel and withdraw. “Later-stage withdrawals can be more costly for developers and can disrupt assumptions built into other projects’ interconnection studies, potentially delaying other projects”, said co-author Rose Strauss, also of Berkeley Lab.
Another concerning trend is that interconnection wait times are on the rise. Interconnection requests now typically take more than 3 years to complete the requisite grid impact studies in most regions, and the timeline from the initial connection request to having a fully built and operational plant has increased from
