Agenda 05-21-24; 8-f - Comment Letter Addressing Duke Energy’s Proposed Carbon Plan Integrated Resource Plan Submitted to the North Carolina Utilities Commission

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18 territory and neighboring utilities, both within Duke's grid planning region (Southeast Regional Transmission Planning, SERTP) and to neighboring transmission planning regions SERTP and PJM. Reports like "The Value of Transmission During Winter Storm Elliott" from ACORE underscore the importance of such connections for improving resilience and reliability, particularly during extreme weather events. Additionally, the joint GE and NRDC study on interregional transmission highlights the vast benefits of expanding interregional transmission throughout the Eastern Interconnection. This approach would not only diversify energy sources and enhance load management but also contribute significantly to the resilience and efficiency of the regional energy infrastructure, all while lowering costs for consumers. By broadening their transmission planning scope, Duke can advance a more sustainable and cost-effective energy future for the Carolinas, and for the broader Southeast region. Proactive, large-scale, long-term transmission planning approaches driven by future generation needs can drive cost-effective power system transformation. For example, the estimated average costs of coordinated onshore wind upgrades for renewables, including up to 17 GW of offshore wind, is significantly lower than the average costs of total network upgrades for current interconnection requests—totaling 15.5 GW offshore wind.27,28,29 This difference implies that proactive, integrated grid planning for larger volumes of capacity additions can offer economies of scale and scope. Planning transmission and generation together can help unlock North Carolina's high offshore wind energy potential in a cost-effective manner. Unit transmission costs of offshore wind expansion could be reduced further by planning appropriately for high-capacity lines to enable access to large resource areas, which would be more efficient than an incremental, piecemeal expansion approach. This could capture economies of scale and reduce redundancies by building fewer lines to support more renewables. Inter-regional coordination and transmission expansion would further reduce cost. Researchers calculate that such approaches could reduce the system cost of electricity in a 100%-renewable US power system by 46% compared with a state-by-state approach.30 Accordingly, the undersigned local governments recommend that the Commission direct Duke to integrate transmission planning into resource planning and procurement as well as plan jointly with neighboring grids. Communities of color and low-income communities often face the most health and environmental impacts from fossil fuel plants and energy infrastructure but often lack the 27 PJM's feasibility and system impacts studies for current interconnection requests totaling 15.5 GW of offshore wind estimate $6.4 billion in total network upgrade costs, which is as high as $400/kW. However, PJM's Offshore Wind Transmission Study published in 2021 estimated the cost of coordinated onshore upgrades for 75 GW of renewables, including up to 17 GW of offshore wind, at$3.2 billion, an average cost of just$40/kW. Such a significant difference implies that proactive, integrated grid planning for larger volumes of capacity additions can offer economies of scale and economies of scope. 28 Based on costs from PJM's feasibility and system impact studies for individual generation interconnection requests as reported in Burke and Goggin, Offshore Wind Transmission Whitepaper, October 2020 at p. 40. 29 PJM, Offshore Transmission Study Group Phase 1 Results, presented to Independent State Agencies Committee (ISAC), July 29, 2021. 30 The Value of Inter-Regional Coordination and Transmission in Decarbonizing the US Electricity System. 16