Study Case Results PC06 High NG Price PC07 Low NG Price W ESTERN E LECTRICITY C OORDINATING C OUNCIL

Overview Study Case Descriptions Impacts to Generation Commitment and Dispatch Impacts to Path Flows Key Observations 2 W ESTERN E LECTRICITY C OORDINATING C OUNCIL

High and Low NG Price Studies Purpose To study the effect of increasing (and decreasing) the natural gas (NG) prices while keeping all other fuel prices at their original values. These study cases were derived from the April 9, 2015 version (v1.5) of the 2024 Common Case. Comparisons are made to that version. 3 W ESTERN E LECTRICITY C OORDINATING C OUNCIL

High and Low NG Price Studies High NG Price (PC06) – Common case NG prices increased by 50% – Example: Colorado average price was increased from 4.91 $/MMBtu to 7.36 $/MMBtu Low NG Price (PC07) – Common case NG prices decreased by 36% – Example: Colorado average price was decreased from 4.91 $/MMBtu to 3.14 $/MMBtu Key Questions – Impact to generation – Impact to transmission 4 W ESTERN E LECTRICITY C OORDINATING C OUNCIL

Comparison of Generation Results 5 W ESTERN E LECTRICITY C OORDINATING C OUNCIL

Change in Generation by state (PC1 to PC6) 6 W ESTERN E LECTRICITY C OORDINATING C OUNCIL The higher gas price triggered some displacement of gas-fired generation by coal-fired generation.

Change in Generation by state (PC1 to PC7) 7 W ESTERN E LECTRICITY C OORDINATING C OUNCIL

8 The difference in NG price is reflected in the total production costs. The CO 2 cost is from the California Global Warming Solutions Act. Change in CO 2 Amount from PC1: High NG price = 2.9% increase Low NG price = 8.6% decrease

Path Flows 9 W ESTERN E LECTRICITY C OORDINATING C OUNCIL

Path (COI plus PDCI) 10 W ESTERN E LECTRICITY C OORDINATING C OUNCIL

Path W ESTERN E LECTRICITY C OORDINATING C OUNCIL

Path W ESTERN E LECTRICITY C OORDINATING C OUNCIL

Path W ESTERN E LECTRICITY C OORDINATING C OUNCIL

Observations 14 W ESTERN E LECTRICITY C OORDINATING C OUNCIL

Observation #1 Decreasing the NG prices had a larger overall impact than increasing the prices. The reduced prices provided closer economic parity between coal and gas generation. Increasing the NG prices extended the economic differential. 15 W ESTERN E LECTRICITY C OORDINATING C OUNCIL

Observation #2 The lower gas prices also had more of an impact on the path flows. Since gas-fired generation is often closer to the load pockets, there was less utilization of the inter-state transmission as a portion of the coal generation was displaced by gas generation. The higher gas prices did impact Path 27 due to increased output from IGS. 16 W ESTERN E LECTRICITY C OORDINATING C OUNCIL

Observation #3 The amount of CO 2 emissions was improved (decreased) with the decreased gas prices in PC07 consistent with a shift from coal-fired to gas-fired generation from the economic dispatch. CO 2 emission rates Coal = 200 lbs/MMBtu Gas = 117 lbs/MMBtu 17 W ESTERN E LECTRICITY C OORDINATING C OUNCIL

Contact Information 18 W ESTERN E LECTRICITY C OORDINATING C OUNCIL Stan Holland (801)