Santee Cooper 2023 Integrated Resource Plan Docket

Sierra Club
Project completed.

Synapse supported Sierra Club’s engagement in Santee Cooper’s 2023 Integrated Resource Plan (IRP) docket before the South Carolina Public Service Commission. Synapse conducted capacity expansion and production cost modeling of Santee Cooper’s electricity system with a focus on evaluating the Company’s decision to delay the retirement of the coal-fired Winyah Generating Station and replace it with a natural gas combined cycle power plant. We discuss how Santee Cooper’s proposed retirement date for Winyah is two years later than its own modeling showed was economically optimal and outline our concerns with some of the Company’s modeling assumptions.

We performed independent modeling of Santee Cooper’s electric system to evaluate an economic retirement date for the Winyah coal plant and develop an optimized clean energy resource replacement portfolio for Santee Cooper that is compliant with the proposed greenhouse gas regulations proposed under section 111 of the clean air act. We found that Santee Cooper did not properly justify its decision to delay the retirement of Winyah from 2026 to the end of 2030. This was due in large part to its failure to develop a truly optimized portfolio, and the Companies input assumptions, that were systematically skewed in favor of fossil resources. Based on our modeling, we find that the Section 11 rules will both increase the cost of, and limit operations of, the Company’s legacy fossil units. Therefore, we find that it will be more economic for Santee Cooper to retire both the Winyah and Cross coal-fired power plants early to avoid costly environmental retrofits and reduce pollution costs.

We recommend that Santee Cooper revisit its IRP and model compliance with the proposed 111 rule. We also recommend that Santee Cooper revised many of its assumptions, including relaxing its renewable build limits, modeling long-duration battery energy storage, updating its ELCCs for battery storage and wind, modeling more up-to-date capital costs for new renewable resources, modeling more realistic capital costs for natural gas resources, and allowing market purchased in its IRP model. Finally, we recommend that Santee Cooper begin issuing an All-Source RFP and focus its near-term procurement efforts on renewable resources.