Queued Up: Characteristics of Power Plants Seeking Transmission Interconnection as of the end of 2020
Joseph Rand, Mark Bolinger, Ryan Wiser, Seongeun Jeong, May 2021 (Lawrence Berkeley National Laboratory)
What are interconnection queues?
Utilities and regional grid operators (a.k.a., ISOs or RTOs) require projects seeking to connect to the grid to undergo a system impact study before they can be built. This process establishes what new transmission equipment or upgrades may be needed before a project can connect to the system and assigns the costs of that equipment. The lists of projects in this process are known as “interconnection queues”.
Developer interest in solar, wind, storage, and gas is strong
Over 755 GW of generator capacity and 200 GW of storage currently seeking interconnection
Most (~680 GW) proposed generation is zero-carbon
Hybrids now comprise a large – and increasing – share of proposed projects
Completion rates are generally low; wait times may be increasing
For five ISOs where data were available, only ~24% of projects in the queues reached commercial operations
Completion rates are even lower for wind (19%) and solar (16%)
For four ISOs where data were available, the time projects spent in queues before being built increased from ~1.9 years for projects built in 2000-2009 up to ~3.5 years for those built in 2010-2020.
Proposed capacity is widely distributed across the U.S.
Substantial proposed solar capacity exists in most regions of the U.S.
Wind capacity is highest in SPP, NYISO, and the non-ISO West, with increasing share of offshore projects
Proposed gas is primarily in the Southeast and PJM
Storage is primarily in CAISO and the West
Methods and Data Sources
Data for “active” projects collected from interconnection queues for 7 ISOs / RTOs and 35 utilities, which collectively represent >85% of U.S. electricity load Projects that connect to the bulk power system: not behind-the-meter Includes all projects in queues through the end of 2020 Sample includes 5,639 “active” projects
• “Completed” and “Withdrawn” project data were only available for 5 ISOs (CAISO, ISO-NE, MISO, NYISO, PJM) Sample includes 1,706 “completed”, and 6,896 “withdrawn” projects.
• Hybrid / co-located projects were identified and categorized Storage capacity for hybrids (i.e., broken out from generator capacity) was not available in all queues
• Note that being in an interconnection queue does not guarantee ultimate construction: majority of plants are not subsequently built
Completed and Withdrawn Projects
Completed and withdrawn data were available from 5 ISOs, and total 1,706 completed projects and 6,896 withdrawn projects
The time from interconnection request (IR) date to commercial operations date (COD) is increasing for some regions and generator types; typically longer for CAISO and for wind
Trends are less evident in time from interconnection request to withdrawn date, though a series of queue reforms from 2010-20121 may have helped reduce backlog
Across the five ISOs studied, just 24% of projects proposed from 2000-2015 have reached commercial operations
The completion rate may have increased temporarily after 2010-2012 queue reforms1 but appears to be declining for projects proposed from 2014-2016. Trends for projects proposed in 2017 and after cannot yet be determined
Increase in completion rates for projects proposed in 2012-2014 is visible across several ISOs; wind (19%) and solar (16%) have lower completion rates from 2000-2015 than other types
Active Projects in Interconnection Queues
Includes data from all 7 ISOs and 35 non-ISO utilities, totaling 5,639 proposed projects
Interconnection queues indicate that commercial interest in solar and storage has grown, including via hybridization; wind and gas have declined
Trends over time vary somewhat by region: Wind capacity has contracted in some regions, solar and storage see consistent growth, gas largely declines
Regional: Proposed solar is widespread, with less in SPP and Northeast; Most wind in SPP with new offshore in NY; Most storage in CAISO, West, ERCOT, and PJM; Gas is largely in the Southeast
State Level: Most proposed solar TX, AZ, IN; proposed wind in TX, “wind belt”, and CA, with offshore in NY; Storage is mainly proposed in CA, TX, NY; Proposed gas in TX and Southeast
71% (653 GW) of total capacity in queues has expected online date by end of 2023; 13% (117 GW) has an executed interconnection agreement (IA)
The median project with an executed IA (but not yet built) has spent 1,387 days in the queues, over 2.5 years more than the median project without an IA (469 days)
Among projects without signed IAs, those in SPP (median = 915 days) tend to have spent the longest time in the queues, followed by MISO (612) and NYISO (602).
Among projects with signed IAs, those in CAISO (median = 2,072 days) tend to have spent the longest time in queues, followed by SPP (1,645), and West (non-ISO) (1,555).
Considerable variation also exists between resource types, with coal, hydropower, nuclear, and wind projects spending the longest time in queues
Among projects without signed IAs, nuclear projects (median = 1,004 days) tend to have spent the longest time in the queues, followed by wind (964)
Among projects with signed IAs, coal projects (median = 4,081 days) are by far the oldest, followed by Hydropower (2,444 days)
Interest in hybrid plants has increased: 34% of solar (159 GW) proposed as hybrids, 6% of wind (13 GW) proposed as hybrids (up from 28% and 5% in 2019, respectively)
Solar+Storage and Wind+Storage configurations are more common than other hybrid types
Hybrids comprise a sizable fraction of all proposed solar plants in multiple regions; proposed wind hybrids dominated by CAISO
• Solar hybridization relative to total amount of solar in each queue is highest in CAISO (89%) and non-ISO West (67%), and is above 20% in SPP and ERCOT
• Wind hybridization relative to total amount of wind in each queue is highest in CAISO (37%) and non-ISO West (13%), and is less than 7% in all other regions
Solar+storage is dominant hybrid type in queues, wind+storage is much less common; CAISO & West of greatest interest so far
Solar+storage projects typically feature a higher storage contribution than wind+storage; POI limits are typically based on generator capacity (at least in CAISO)
Storage capacity for hybrid projects was provided in a subset of queues. Where available, we calculated the ratio of storage capacity to generator capacity. Median storage:generator capacity ratio for solar+storage (60%) is higher than for wind+storage (35%), and the ratio is generally higher where solar penetration is higher.
Point of interconnection (POI) capacity limits were only provided in CAISO’s queue. For solar+storage projects, the solar capacity alone equals or exceeds the POI limit in 91% of projects, and the median combined (solar+storage) capacity is double (200%) the POI limit. For wind+storage projects, the wind capacity alone equals or exceeds the POI limit in 67% of projects, and the median total (wind+storage) capacity is 126% of the POI limit. These values suggest that these projects are maximizing their POI limit by using storage to supply power at times when the generator is not generating
As of the end of 2020, there were over 5,600 projects seeking grid interconnection across the U.S., representing over 755 GW of generation and an estimated ~204 GW of storage.
• Solar (462 GW) accounts for >60% of all active generator capacity in the queues, though substantial wind (209 GW) and gas (74 GW) capacity is also in development. Notably, 29% of the wind capacity in the queues is for offshore projects (61 GW).
• Considerable standalone (89 GW) and hybrid (~112 GW1) battery capacity is also in development, along with 4 GW of other storage.
• Growth in proposed solar and storage capacity is consistent across regions. Proposed wind has contracted in some regions, but continues to grow in those with proposed offshore development. Gas is declining in all regions except for non-ISO Southeast.
• Hybrids now comprise a large – and increasing – share of proposed projects, particularly in CAISO and non-ISO West. 159 GW of solar hybrids (primarily solar+battery) and 13 GW of wind hybrids are in the queues.
• The vast majority (71%) of capacity in the queues has requested to come online by the end of 2023, and some (13%) already has an executed interconnection agreement.
• The time projects spend in queues before reaching COD may be increasing. For the four ISOs studied2, the typical duration from IR to COD went from ~1.9 years for projects built in 2000-2009 up to ~3.5 years for those built in 2010-2020.
• More than half (671 GW) of the estimated 1,100 GW of wind and solar capacity needed to approach a zero-carbon electricity target is already in development3.
• Ultimately, much of this proposed capacity will not be built. Historically only ~24% of projects in the queues reached commercial operations, and less for wind (19%) and solar (16%). There are growing calls for queue reform to reduce cost, lead times, and speculation.