Report shows record renewable energy capacity proposed in interconnection queues

The amount of proposed power plant capacity lined up to connect to the electric grid across America has risen dramatically. As of the end of 2020, projects with more than 755 GW of electric-generating capacity and an estimated 200 GW of storage capacity were seeking access to the U.S. transmission system, according to new research by Lawrence Berkeley National Laboratory (Berkeley Lab). Nearly 90% (671 GW) of this proposed generating capacity is from solar (462 GW) and wind power plants (209 GW).

“Together, this proposed capacity represents more than half of the estimated 1,100 GW of wind and solar capacity that studies say is needed to deeply decarbonize the U.S. electricity supply,” said Joseph Rand, a senior scientific engineering associate at Berkeley Lab and lead author of the study. “But our research also points to increasing lead times, high rates of withdrawn projects, and a large backlog of projects in the queues, which could be a potential bottleneck in the transition to zero-carbon electricity in the United States.”

Large power plants and storage projects must connect to the electric grid to supply power to electricity consumers such as homes and businesses. Before connecting to the grid, proposed projects must apply to the grid operator, who then conducts a series of impact studies. The lists of projects applying for interconnection are known as “interconnection queues.” While many projects that apply for interconnection are not subsequently built, data from these queues nonetheless provide a general indication of the types of projects under development.

A bar graph showing total capacity in gigawatts in interconnection queues from 2015 to 2020, identified by technology (i.e., solar, wind, gas, etc.).

Total capacity in interconnection queues over time. Hybrid storage capacity was estimated for some projects using known generator-to-storage ratios, but not for years prior to 2020. Image from Lawrence Berkeley National Laboratory (Berkeley Lab)

Berkeley Lab compiled and analyzed data from all seven large regional grid operators (known as independent system operators, or ISOs) in addition to 35 utilities not in ISO regions, together serving an estimated 85% of all U.S. electricity demand.

Solar (462 GW) accounts for a large and growing share of generating capacity in the queues. Substantial wind capacity (209 GW) is also in development, 29% (61 GW) of which is from offshore projects. In total, about 680 GW of zero-carbon capacity is currently seeking to connect to the grid, along with 74 GW of natural gas capacity. Proposed wind capacity is highest in New York (driven by offshore wind energy projects), the Great Plains, and the West, but with sizable amounts proposed in all regions except the Southeast, which has lower wind speeds. Although the amount of wind capacity in interconnection queues has decreased in some regions, it continues to grow in those with proposed offshore wind projects, such as the Northeast and Pacific Coast.

Two maps of the United States. One shows the total wind capacity in interconnection queues at the end of 2020, measured in gigawatts. The other shows new wind capacity added to interconnection queues in 2020, measured in gigawatts.

Location of cumulative proposed wind energy capacity at the end of 2020 (left) and of wind capacity that was first proposed in 2020 (right). Image from Berkeley Lab

Hybrid power plants—those that combine two or more power plant types (such as wind and solar) and/or pair a power plant with electric storage (most often comprising batteries)—are of growing interest. At least 34% (159 GW) of all solar power capacity in the queues and 6% (13 GW) of wind power capacity are proposed as a hybrid plants.

A bar graph showing the proportion of capacity in queues in a hybrid configuration, indicating solar at 34.4%, wind at 6.3%, storage at 54.6%, natural gas at 5.7%, and other at 14.8%.

Proportion of capacity in queues in a hybrid configuration as of the end of 2020. Hybrid storage capacity was estimated for some projects using known storage-to-generator ratios. Image from Berkeley Lab

“While the numbers are impressive, much of this proposed capacity will never be built,” said Ryan Wiser, a senior scientist at Berkeley Lab and coauthor of the report.

For context, among a subset of queues for which data are available, only 24% of the projects seeking interconnection from 2000 to 2015 were subsequently built. Completion percentages appear to be declining and are even lower for wind and solar than for other resources. Future research may determine the exact reasons why so many projects are withdrawn, but the available data do provide some insights.

“We know that the U.S. transmission system is constrained in many regions, and the upgrades required to connect new power plants can be very costly,” said Rand. “And the developers of these proposed projects might be submitting multiple ‘placeholder’ projects to collect information on which to proceed.”

Additionally, wait times are on the rise for projects that are built.

“In four regions that we studied, the typical duration from interconnection request to commercial operation increased from about 1.9 years for projects built from 2000 to 2009 to about 3.5 years for those built between 2010 and 2020,” said Mark Bolinger, a research scientist at Berkeley Lab and coauthor of the report.

For these reasons, there are growing calls from power plant developers, nonprofit organizations, and policymakers for queue reform—and with it, an expansion of the transmission system. Such reforms would aim to reduce interconnection costs, lead times, and placeholder projects in the queues and, therefore, better enable the rapid transition to a clean energy future. In July 2021, the Federal Energy Regulatory Commission announced plans to overhaul the U.S. transmission planning process—of which the interconnection queues are a backbone.

These research findings are summarized in a slide deck, data file, and interactive visualization on the Berkeley Lab website.

Fall 2021 R&D Newsletter

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