Brattle study finds similar summer reserve margins and lower winter risk in alternative EDAM footprint; NV Energy petitions PUCN over implementation cost rules

David Rubin, a representative for NV Energy, briefed the Regional Transmission Coordination Task Force on the company's pending application with the Public Utilities Commission of Nevada (PUCN) to join the California ISO's extended day-ahead market (EDAM), and described two petitions for reconsideration of the PUCN's April order. Rubin said one petition is from NV Energy seeking reconsideration of the cost-treatment of charges tied to potential failures of the resource-efficiency test and the company's ability to spend funds on EDAM implementation in 2026; a second petition, filed by a coalition including Nevada Gold Mines and the Southern Nevada Water Authority, seeks tariff approvals prior to the PUCN's final authorization.

The task force then heard a presentation from Kai Van Horn of the Brattle Group summarizing a study comparing planning reserve margin (PRM) outcomes across multiple western footprints, including RAP subregions, the full RAP footprint, and a non-CAISO EDAM footprint. Brattle modeled resource adequacy using hundreds of thousands of hourly outage and weather simulations and replicated RAP'style methodology for apples-to-apples comparisons. "For the summer, we saw similar PRMs across the footprints," Van Horn said. "In the winter we observed lower PRMs in the non-CAISO EDAM footprint, driven primarily by differences in timing of risk and resource mix."

Van Horn emphasized modeling caveats and potential enhancements: the Brattle team followed RAP practice and assumed unconstrained transmission within footprints for the PRM calculations, and recommended future analyses incorporate transmission limits, temperature-dependent thermal outage rates and a refined treatment of non-firm imports to better assess deliverability and true regional support during emergencies. "We followed the RAP methodology, which assumes no limits on transmission connectivity," he said, noting that contracting parties must still show transmission rights when they sign capacity contracts.

Rubin summarized the PUCN conditions attached to NV Energy's approval: a moratorium on implementation spending until Jan. 1, 2027; caps on implementation and incremental O&M costs subject to PUCN modification; and an automatic disallowance for costs arising from resource-efficiency-test failures as the order was written. NV Energy has asked the commission to allow prudence review of those failures rather than an automatic disallowance, arguing there may be circumstances beyond the company's control.

Why it matters: resource adequacy and EDAM participation are central to Nevada's statutory timeline for regional market integration. Under SB448, NV Energy must be part of an RTO by Jan. 1, 2030, unless it files an application by Jan. 1, 2027 showing a viable waiver or delay. The Brattle analysis indicates that PRM differences across plausible footprints are nuanced: summer margins are broadly comparable, but winter risk timing and resource mixes (including storage penetration) materially affect outcomes and the value of regional diversity.

What's next: Brattle identified near-term outreach and workshops on governance, modeling and compliance that will inform ROE design and resource-accreditation details. NV Energy awaits a PUCN decision on the petitions for reconsideration, expected by the end of May, and must align implementation spending with the PUCN'ordered caps and timing if the order stands.