Study Results PC8-PC16 System Stress Tests This slide deck contains results from the 2012 TEPPC Study Program related to the various stress tests performed on the 2022 Common Case. The results of the studies are shown along with an indicator to show the robustness of transmission in that area.

10-Year Stress Test Results Description and goal Assumptions Results

Study Description and Goal

Stress Test Cases – two concepts… PC8-PC15 – Add 6,000 GWh Renewables PC16 – RPS Off-Ramp

Summary “Examine the Robustness of the Power Grid” Evaluate system’s ability to integrate and deliver added resources to load, subject to transmission constraints “Stress” the system Proxy for High gas (makes RE more competitive) High load (requires higher RPS and more RE) CO2 Policy (less thermal, more RE) Increase in RPS (more RE) Studies are designed as indicators Help us to understand how the system may behave under a variety of future conditions. This is robust planning.

Caveats No additional transmission added Small addition of RE will not solely justify addition of large interregional project Capital cost analysis will not be performed as it is outside the intent of the study

Study Assumptions

Stress Test: PC8-PC15 Resource Selection Process Calculate ratios of renewables in TEPPC 2022 Common Case Do not include existing resources Do not include DG IRP and LRS data Apply ratio to future build-out of 6,000 GWh Concept: past trends are best the representation of what could be added to each state More recourses available than what is identified in WREZ More granular information from CPUC/CAISO Locate resources using WREZ Extrapolation Method

Resources from CPUC scenario that were originally decremented for Common Case net-short are added Solar +1000 GWh Evaluated as one 6,000 GWh study. Resource split 50/50 in each Basin state. Per CPUC Geothermal -1000 GWh

Stress Test: PC16 Resource Removal Process WECC Class Explanation Class 0 Existing Class 1 Under active construction. Projected to be in-service within five years. Class 2 Additions that were reported to have: Regulatory approval (or in review) Signed Interconnection agreement Expected on-line date within seven years Class 3 Meet NERC criteria for Future Planned or Future Other Resources but that do not meet Class 1 or 2 Class 4 Meet NERC criteria for Conceptual Resources Remove WECC LRS Data Collection Manual

Common Case Results Refresher

Selection based on → Implementation Indicators Construction Status Financial Indicators Implementation Indicators Selection based on → Regional Significance

Potential “area of concern” High utilization can be explained or is expected

Flow: NW to BC Flow: BC to NW

IPP generation

CA gas units are “most marginal.” Common Trends 1 System seems to be fairly robust given the CCTA and Common Case starting point of system utilization. 3 Heavier utilization, not much congestion (i.e., the transmission system still permits economic transfer). 2 When more renewable energy is added to the system, gas appears to be the marginal resource in all studies (except Montana), given our current price assumptions. CA gas units are “most marginal.”

California Stress Test Assumptions Transmission Results Generation Impacts Key Finding Stress test had only minor impact on transmission utilization. Including additional generation in CA reduces requirement for imports. Robustness Indicator

Arizona Stress Test Assumptions Transmission Results Generation Impacts Key Finding Increase in AZ to CA imports. Congestion on P29. More detailed analysis required. Robustness Indicator

New Mexico Stress Test Assumptions Transmission Results Generation Impacts Key Finding Increase in P22 (SW of 4-Corners) utilization, but not congested. Other paths are not heavily impacted. Robustness Indicator

Wyoming Stress Test Assumptions Transmission Results Generation Impacts Key Finding Some sensitivity observed – P29 and P36. Large change in RMPA to Basin flow. Robustness Indicator

Montana Stress Test Assumptions Transmission Results Generation Impacts Key Finding Robustness Indicator P8 congested as a result. MT system is relatively isolated and is easily stressed.

Washington Stress Test Assumptions Transmission Results Generation Impacts Key Finding Small impact. Robustness Indicator

Very little congestion observed. Oregon Stress Test Assumptions Transmission Results Generation Impacts Key Finding Very little congestion observed. Robustness Indicator

Increased utilization, but not much congestion. Basin Stress Test Assumptions Transmission Results Generation Impacts Key Finding Increased utilization, but not much congestion. Robustness Indicator

RPS Off-Ramp Stress Test Assumptions Transmission Results Generation Impacts Key Finding Decrease in congestion outweighs increase. Side bar: Is it apparent that our system designed for “RPS compliance” is highly versatile and can accommodate more “local” generation? Robustness Indicator

Quick Summary NA NA Robustness Indicator NA NA

Questions or thoughts on this study?