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

2. 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

3. 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

4. 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

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

6. 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.

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

8. 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

9. Path Flows 9 W ESTERN E LECTRICITY C OORDINATING C OUNCIL

10. Path 66+65 (COI plus PDCI) 10 W ESTERN E LECTRICITY C OORDINATING C OUNCIL

11. Path 46 11 W ESTERN E LECTRICITY C OORDINATING C OUNCIL

12. Path 27 12 W ESTERN E LECTRICITY C OORDINATING C OUNCIL

13. Path 26 13 W ESTERN E LECTRICITY C OORDINATING C OUNCIL

14. Observations 14 W ESTERN E LECTRICITY C OORDINATING C OUNCIL

15. 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

16. 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

17. 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

18. Contact Information 18 W ESTERN E LECTRICITY C OORDINATING C OUNCIL Stan Holland (801) 883-6858 stan@wecc.biz