PC21 Coal Retirement Study TAS/TEPPC – Nov W ESTERN E LECTRICITY C OORDINATING C OUNCIL WECC System Adequacy Planning

Overview Study Description › Scope › Input assumptions › Study qualifications Study Results › Details Generation Paths Other Observations 2 W ESTERN E LECTRICITY C OORDINATING C OUNCIL

Study Description 3 W ESTERN E LECTRICITY C OORDINATING C OUNCIL

Study Description - Purpose Model a scenario that approaches the 2024 trajectory of reducing carbon emissions to 80% below the 2005 levels by W ESTERN E LECTRICITY C OORDINATING C OUNCIL 248 in 2024

Study Description - Assumptions Modeling assumptions include: – Retirement of several high CO 2 intensity coal-fired generators based on vintage and location – Addition of renewable resources (wind + solar) – Additional energy efficiency – Addition of gas-fired generation – Addition of energy storage resources – More details on next slides 5 W ESTERN E LECTRICITY C OORDINATING C OUNCIL

6 ABAZCACOMTUTWY Battle River 4,5 [537] Apache 2,3 [350] ACE Cogen [103] Comanche 1,2 [660] Colstrip 1,2,3 [1354] Huntington 1,2 [909] Dave Johnston 1-4 [762] Genesse 2 [390] Cholla 1,3 [387] Argus 8,9 [50] Craig 1,2 [863] Intermountain 1,2 [1800] Jim Bridger 1,2,3 [1581] Sheerness 1,2 [780] Coronado 1 [380] Casterville [1] Hayden 1,2 [446] NM KUCC 1-4 [175] Naughton 1,2 [357] Sundance 3 [362] H.W. Sundt 4 [156] Fellow [1] M Drake 5,6,7 [254] Four Corners 4,5 [1540] Sunnyside [53] Neil Simpson 2 [80] Navajo 2,3 [1500] Jackson Valley [21] Nucla 1-4 [100] Wygen 1,2 [180] Lassen [22] R D Nixon 1 [208] NVWA Wyodak [340] Mt Poso [35] N Valmy 2 [268] Centralia 2 [688] Phillips Carbon [16] TS Power 1 [227] Portland Cement [28] Port of Stockton [44] PC21 Additional Coal Retirements

PC21 Coal Retirements by State/Province 7 W ESTERN E LECTRICITY C OORDINATING C OUNCIL

Replacement Sources 8 W ESTERN E LECTRICITY C OORDINATING C OUNCIL The Retired MWh represents the energy produced by the PC21 retired coal resources in the 2024 v1.5 common case. The EE energy was modeled as a load reduction and resulted in a total reduction of about 1700 GWh.

Study Qualifications Path Ratings: The WECC paths associated with a few of the retired generators and their replacements would likely need to be re- rated through the path rating process. No changes in path or branch ratings were assumed for this study. Constraints: Other operating constraints and nomograms were also not modified. Flexibility Reserves: The flexibility reserve adders for each reserve area are derived from the loads and amount of variable generation. The flexibility reserve adders were not recalculated for this study. Resource Adequacy: A check of the peak planning reserve margins was not done. System Stability: Tests of system stability were not conducted. 9 W ESTERN E LECTRICITY C OORDINATING C OUNCIL

Results 10 W ESTERN E LECTRICITY C OORDINATING C OUNCIL

Dump Energy ReservesNomogramsCostDeliverableConstraints 11 W ESTERN E LECTRICITY C OORDINATING C OUNCIL Generation that is chosen by the PSM model for commitment and dispatch for a least-cost solution may be dumped if its dispatch will break a modeling constraint regarding generation, transmission, reserves, and/or nomograms.

12 W ESTERN E LECTRICITY C OORDINATING C OUNCIL From New Gen 0 269, ,409,645 1,801, Load side ,820,604 38,636,263 61,938, ,356 -1,731,070

Category Change – Estimated/Actual 13 W ESTERN E LECTRICITY C OORDINATING C OUNCIL

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Generation Comparison 15 W ESTERN E LECTRICITY C OORDINATING C OUNCIL

Difference in Annual Energy - WECC 16 W ESTERN E LECTRICITY C OORDINATING C OUNCIL

2024 CO 2 PC21 Coal Retirement Case 17 W ESTERN E LECTRICITY C OORDINATING C OUNCIL

Generation Change by State and Fuel 18 W ESTERN E LECTRICITY C OORDINATING C OUNCIL

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20 W ESTERN E LECTRICITY C OORDINATING C OUNCIL This was the only replacement ES unit that had any significant operation. The others didn’t seem to reach the price thresholds.

WECC Paths 21 W ESTERN E LECTRICITY C OORDINATING C OUNCIL

Top 15 Heavily Utilized in PC21 22 W ESTERN E LECTRICITY C OORDINATING C OUNCIL

Comparison of Net Annual Flow – Top 15 U90 23 W ESTERN E LECTRICITY C OORDINATING C OUNCIL

Path 8 24 W ESTERN E LECTRICITY C OORDINATING C OUNCIL The retirement of the base load generation at Colstrip 1,2,3 had an impact on the Path 8 flows. It is also possible that the path rating would be reduced.

Path (COI plus PDCI) 25 W ESTERN E LECTRICITY C OORDINATING C OUNCIL

Path W ESTERN E LECTRICITY C OORDINATING C OUNCIL In the past a nomogram has been used to define a relationship between generation and path 27 flows. The nomogram was not modified to specify how the replacement generation in Utah would be treated with respect to southern California.

Path W ESTERN E LECTRICITY C OORDINATING C OUNCIL

More Results 28 W ESTERN E LECTRICITY C OORDINATING C OUNCIL

WECC Peak Week 29 W ESTERN E LECTRICITY C OORDINATING C OUNCIL

WECC Peak Hour – PC21 30 W ESTERN E LECTRICITY C OORDINATING C OUNCIL

WECC Early April 31 W ESTERN E LECTRICITY C OORDINATING C OUNCIL

Dump Energy 4/7/24 – PC21 32 W ESTERN E LECTRICITY C OORDINATING C OUNCIL

Peak hour on April 2 – WECC PC21 33 W ESTERN E LECTRICITY C OORDINATING C OUNCIL

California Peak Week 34 W ESTERN E LECTRICITY C OORDINATING C OUNCIL

California Early April 35 W ESTERN E LECTRICITY C OORDINATING C OUNCIL The gaps between the demand and generation represent energy imports. The hours where the generation exceeds the demand represents exports.

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Observations The PC21 study had no unserved load. PC21 CO 2 was 29 million metric tons short of goal Overall energy from PC01 CC and CT units increased Overall energy from remaining coal units increased Share of annual energy from renewable resources is 23.1% in PC21 vs. 17.7% in PC01 Poor performance of PC21 pump storage projects except for project added in SRP area 37 W ESTERN E LECTRICITY C OORDINATING C OUNCIL

38 W ESTERN E LECTRICITY C OORDINATING C OUNCIL Contact Stan Holland Western Electricity Coordinating Council Senior Engineer (801) Stan Holland Western Electricity Coordinating Council Senior Engineer (801)