TAS Quarterly Meeting Further Investigation of Load and Energy Shapes for use in the 2026 Common Case November 4-5, Tom Miller- TAS Vice Chair W ESTERN E LECTRICITY C OORDINATING C OUNCIL Holidays Kick Off ! NET LOAD THANKSGIVING DAY OVER STUFFING 3-Hour Ramp-Rate: Million lbs Duck-free Presentation Discussion 1.Overview Energy Shape Investigation 2.Fundamental Energy Shape Attributes 3.California Load Attributes Developing Criteria for Load Shapes Peak Load Months and Heating/Cooling Days vs 2009 Northwest Energy Shapes Typical Northwest Load and Wind Compare Northwest Hydro 5.Insights from CEC, CAISO and NREL 6.Alternate Perspective 7.Lessons learned and Next Steps 8.Wrap-up 9.Proposals 3 W ESTERN E LECTRICITY C OORDINATING C OUNCIL Overview: Energy Shape Investigation Draft Proposal for Further Investigation: Define Goal and Object for selecting typical load shape year that characterizes typical energy load shapes (peaks/energy) Develop criteria for picking a load shape year: Load attributes for WECC-wide sub-regions E.g. NW Winter Peaking vs. CA/SW Summer Peaking Attributes of updated NREL wind/solar data Investigate Historical Load Attributes: Years (updated NREL wind/solar) Each Load Area: monthly energy, peak MW, peak-hour Sub-region Peak: coincidental peak-MW for each load area California: coincidental peak for each load area WECC Peak: coincidental peak-MW for each load area Discussion on need for Hydro data to be coincident: hear from the experts (Michael Milligan, Arnie Olsen, Others) Alternative Proposals: define and present for discussion Develop Recommendation/ alternative proposals What was Accomplished: Reached out to CA Stakeholders to better understand their concerns and perspectives TAS Follow-up Discussions WECC BA Peak Month assessment California Cooling Degree Days Great Recession Alternate proposal Presentation Success: Provide stakeholders additional information and opportunity to discuss attributes of candidate energy shape years Seek consensus Propose alternative proposal to be considered for Todays TAS Vote 4 W ESTERN E LECTRICITY C OORDINATING C OUNCIL Fundamental Energy Shape Attributes 5 W ESTERN E LECTRICITY C OORDINATING C OUNCIL Annual Hydro Energy Typical CA Load Peak MonthNon Typical CA June Peak Typical WECC-wide April NW Hydro Non Typical (Low) ~ (-) 4000 aMW Typical: Aligns with Historical Avg. April NW WindTypical: Aligns with Historical Avg. Lower than Typical: ~ (-) 100 aMW June NW Hydro Non Typical (High) ~ aMW Typical Aligns with Hist. Avg. June NW Wind Non Typical (High) ~ aMW Typical Aligns with Hist. Avg. Updated NREL Wind SolarAvailable (Pro) Load Criteria Development 6 W ESTERN E LECTRICITY C OORDINATING C OUNCIL What Criteria do Planning Regions Plan to? Summer/Winter Peak Mw? Energy? Load-net wind-solar Peaks? Table shows assessment of Annual Peak Month Non-Typical Peak Month Typical Peak Month Load Criteria Development 7 W ESTERN E LECTRICITY C OORDINATING C OUNCIL 2008 California Major Load Centers June Peak not typical Conclusion: 2009 is a better representative year over 2008 regarding typical system peak months CA Annual Cooling Days 8 W ESTERN E LECTRICITY C OORDINATING C OUNCIL Conclusion: both 2008 and 2009 are good candidate years regarding CA CDDs Load Impact to Temperature Cooling Degree Day: sum of the absolute distance from 65 degrees that the days midpoint temp has for a given area: CA IOUs, SMUD, LADWP, Burbank, Glendale, Pasa, IID Typical Northwest Wind and Loads 9 W ESTERN E LECTRICITY C OORDINATING C OUNCIL Wind: Northwest (WA+OR) WECC-Wide Stress: In California-Southwest, the system is more prone to over- generation (with high solar and low load in April). In Northwest, it is also more likely to have over-generation (with higher wind) in April than in June. NW Hydro 10 W ESTERN E LECTRICITY C OORDINATING C OUNCIL Concerns Non-typical NW Hydro Monthly Shape April 2008: Below typical NW Hydro may under-state over- generation issues in the Northwest (Wind) and Southwest/California Regions (Low Load/High Solar) June 2008: late runoff and above average my stress flows across COI and CA 500/230kv Backbone Conclusion: 2009 better representative of typical year that has benefits for all regions to assess April stress 2008 June NW Wind highest for all years (~ +30% > Hist. Avg.) April Highest Avg. NW Wind California Energy Commission California Energy Commission (CEC) Mike Jaske CEC load forecasters have never authored hourly shapes Users of CECs official peak load and annual energy load forecasts use their own discretion on how to come up with loads on an 8760 basis. CEC staff provided monthly peak projections (and I believe energy) to the ISO for the ISO to use in reporting to WECC, but are not published CEC project to develop the capability to make 8760 projections: Vendor has been selected (via RFO). Project will take time to develop and No official base load forecast shapes will be available for another year or so. Recognizing that AAEE load shape is an important assumption, and is likely to be considerably different from the base load shape CEC is developing an interim capability for the new AAEE projections for the TPP to provide 8760 shapes for those specific assumptions. 11 W ESTERN E LECTRICITY C OORDINATING C OUNCIL California ISO California ISO (CAISO) David Le For future scenario, load analyses from the CEC demand forecasters are critical to establish a baseline load shape for California. Trying to use historical load shape, as well as wind and others, for the future, with renewable additions, may not provide a representative of the future load shape. In addition, to understand load shapes correctly, we will need to incorporate temperature data as well as economic forecast comparison. Since the demand for production cost simulation is a 1:2 heat wave loads, we have yet to see how the historical load shapes trend with the 1:2 heat wave projection. Given that were short on time for the 2026 CC case, Id suggest using 2009 for the baseline load shape for now, and performing a sensitivity study with the 2008 load shape. Even with the 2009 load (hydro, and so on) shapes, we still do not have very rigorous analyses to establish a baseline assumption for the ten- year future. This will need to be an action item before the next Common Case 12 W ESTERN E LECTRICITY C OORDINATING C OUNCIL National Renewable Energy Lab NREL- Michael Milligan My view is modeling must have a plausible, realistic depiction of load/wind/solar/hydro. In the case of wind and solar, the complexities of the resource make it difficult to parameterize them to ensure on any given modeled day, the underlying weather that drives wind, solar and demand, is consistent. Coupled with the fact that wind and solar are generally "as delivered" resources, there is not as much opportunity to dispatch them - although it is important to note that both wind and solar can now be used to provide regulation and even ramping if it is economic. Hydro is fundamentally different from wind/solar because it is partially controllable - much more so than wind/solar in the dispatch/commitment time frames. Both the HTC and PLF algorithms recognize and implement that, subject to monthly energy budgets, ramp constraints, etc. on the hydro system..that leaves the question of whether and how hydro coincident data should be used. Note that in a year of high rainfall, there are complex time lags between the time of rainfall and the time that water can be used along a river basin - anywhere from hours to weeks (or maybe months. Some analysis that would analyze the annual correlation between wind, solar, and hydro energy would help inform the decision as to how to handle hydro in the modeling framework 13 W ESTERN E LECTRICITY C OORDINATING C OUNCIL Lessons Learned Gridview modeling of monthly peak-MW and energy helps mitigates concern over 2008 CA June peak Issues Need to develop regional criteria for load shapes Load Forecasting Expertise Need to develop dispatch attributes of wind/solar Reported load forecasts need to be vetted for use in TEPPC data-set Implied Load Modifiers: EE, BTM-PV Incremental Modeling: EE, BTMPV, Other Understand underlying assumptions: economic, temperature (1 in 2) adjusted Need for WECC Staff time for load assessments 14 W ESTERN E LECTRICITY C OORDINATING C OUNCIL Expanding Footprint of Centralized Dispatch Geography Changing Resource Mix Sep- 17 th CA SB 350 CA 50% RPS GWh BTM-PV Electric Vehicles EPA CPP 111d BPA+ = BPA + CHPD + DOPD + GCPD + SCL + TPWR Alternative Perspective Source: California ISO Source: EPA Clean Power Plan WECC Phase Preliminary Technical Report NEXT Steps 2026 Common Case Energy Shape Implementation Smart Goals development Smart Goal: Measurable, Attainable, Relevant, Time-bound): Understanding WECC Load Forecast Data Investigate 2026 Common Case Load Forecasts Shapes TAS Process Improvements for Load Assessments 16 W ESTERN E LECTRICITY C OORDINATING C OUNCIL Wrap-up 17 W ESTERN E LECTRICITY C OORDINATING C OUNCIL Annual Hydro Energy Typical CA Load Peak MonthNon Typical CA June Peak Typical WECC-wide April NW Hydro Non Typical (Low) ~ (-) 4000 aMW Typical: Aligns with Historical Avg. April NW WindTypical: Aligns with Historical Avg. Lower than Typical: ~ (-) 100 aMW June NW Hydro Non Typical (High) ~ aMW Typical Aligns with Hist. Avg. June NW Wind Non Typical (High) ~ aMW Typical Aligns with Hist. Avg. Updated NREL Wind SolarAvailable (Pro) Proposals TAS Vote: 2008 Coincident Load-Wind-Solar- Hydro based on NW Proposal (August) New Proposal 2009 Coincident Load-Wind- Solar-Hydro based on original proposal (April 28) 18 W ESTERN E LECTRICITY C OORDINATING C OUNCIL Questions or Comments 19 W ESTERN E LECTRICITY C OORDINATING C OUNCIL Reference Slides 20 W ESTERN E LECTRICITY C OORDINATING C OUNCIL The Great Recession 21 W ESTERN E LECTRICITY C OORDINATING C OUNCIL Conclusion: Great Recession impacted both 2008 and Open question on how. Northwest Monthly Wind 2008: Peak wind in Jun coinciding with peak Hydro 2009: Peak wind in Mar and below median in spring 22 * Red font denotes difference is greater that a standard deviation from median SOURCE: TAS Review Load and Hydro Shapes for use in TEPPC 2026 Common Case by Kevin Harris