Duke Energy 2025 Biennial Consolidated Carbon Plan and Integrated Resource Plan (CPIRP) for North Carolina
On behalf of the North Carolina Sustainable Energy Association (NCSEA), Synapse provided expert testimony in Duke Energy’s 2025 Biennial Consolidated Carbon Plan and Integrated Resource Plan (CPIRP). For this docket, Synapse reviewed the Company’s modeling and conducted out own independent modeling using both the EnCompass capacity expansion and production cost model, as well as SERVM to conduct reliability modeling.
Synapse focused on evaluating Duke’s input assumptions, modeling methodology, and final portfolios. We assessed the reasonableness of the Companies’ proposed resource build and demand-side management (DSM) and energy efficiency investment plans. We assessed whether the Companies are accurately reflecting the costs, risks, and volatility impacts of their planned reliance on gas resources through their modeling. We then presented the results of NCSEA’s alternative analyses. Both the NCSEA Alternative Portfolio and the NCSEA Combined Utility Portfolio represent least-regrets futures that meet the energy and reliability needs of the Companies’ high and growing load forecast with fewer new gas generation resources and increased investment in energy efficiency. The NCSEA portfolios maintain a viable path to the 2050 net-zero carbon emissions requirement and result in a lower cost to ratepayers than Duke Energy’s Recommended Portfolio.
We found that Duke is scaling back its investment in solar PV in the near and intermediate term (2026-2034) by 2,460 MW. Over the same timeframe, the Company is increasing its investment in battery energy storage (1,900 MW) and gas generation (700 MW), relative to its prior (2023) CPIRP. We found that the Company’s projections around load growth between now and 2040 have increased by more than 2,000 MW since the last CPIRP and are driving the Company to delay coal plant retirements and build more new gas assets. Our additional findings on Duke’s modeling were that (1) the Company does not have sufficient firm gas capacity to supply its projected gas demand, (2) it is relying on overly optimistic assumptions around the cost of nuclear generation, (3) Duke is planning to continue to underinvest in DSM; inaction by the Company has driven the delay in the deployment timeline for Bad Creek 2.
Based on Synapse’s independent modeling in EnCompass, we found that the NCSEA Alternative Portfolio, which includes increased investment in energy efficiency, demand side management, expanded PowerPair program resources and the addition of Bad Creek 2 in 2037, results in less natural gas and few nuclear resources than in Duke’s Recommended Portfolio. Based on our independent modeling in SERVM, we confirmed that this alternative portfolio achieved Duke’s reliability threshold.
Based on these findings, we recommended that Duke revise its Recommended Portfolio to (1) incorporate higher levels of energy efficiency and DSM investment, more aligned with levels modeled in its high energy efficiency and high DSM scenarios; (2) model accelerated and increased deployment of the PowerPair program; and (3) include Bad Creek II as a resource in the late 2030’s. We also outlined recommendations for the Commission for Duke to monitor the cost of operating its legacy resources, and better justify its assumptions around nuclear technology and its firm gas supply.