A new report by experts at The Brattle Group examines how the Southeast region in the U.S. can cost-effectively meet growing electricity demand, continue deploying low-carbon resources, and maintain resource adequacy through the 2040s.
Prepared for GridLab, Southeast Energy Vision: Achieving Reliability and Net Zero Emissions while Supporting Rapid Load Growth, evaluates the region’s resource needs through 2040 under a range of future conditions, including load growth, generation retirements, extreme weather, transmission constraints, regional coordination, and demand flexibility.
The analysis finds that annual solar development must double to keep up with demand growth and clean, firm resources, including nuclear, are part of a more cost-effective generation mix.
The report evaluates the Southeast at a regional and zonal scale and deploys in simulating resource adequacy risks and a cost-minimizing, weather-resilient long-term resource portfolio.
Specifically, Brattle experts utilized the firm’s capacity expansion model gridSIM, together with its Weather-Reflective Resource Adequacy Sampling (WRAS) methodology, to endogenously capture resource adequacy risks that conventional planning approaches may overlook.
The analysis evaluates hourly system needs drawn from 15 weather years, including heat waves, winter cold snaps, and periods of low renewable production. It also considers how increased utilization of existing regional transmission capacity and flexible demand can help address resource adequacy challenges over the coming decades.
The authors find that the Southeast’s most significant future resource adequacy challenges are likely to arise when winter cold snaps occur during renewable generation droughts, rather than summer peak periods.
During such winter events, high heating demand can coincide with greater thermal generation outage risk and limited solar production, increasing the importance of firm resources, storage, transmission, regional trading, and flexible demand.
Among the report’s key findings:
• Resource adequacy challenges in the Southeast are increasingly driven by weather risk and energy supply limitations, rather than by peak loads. Risks are concentrated during extended winter cold snaps, particularly overnight when demand remains elevated and solar generation is unavailable. They also emerge during renewable droughts, temperature-correlated fossil outages, and prolonged heatwaves. Effective Southeast resource planning thus requires evaluating multi-day periods at hourly granularity and across a broad geographic scope.
• A lower-emission resource portfolio can cost-effectively maintain resource adequacy. Continued deployment of clean resources in the Southeast can support growing demand and help address severe-weather reliability risks while reducing emissions. Significant additions of solar and storage, complemented by firm generation, are important elements of the projected cost-effective mix.
• Firm resources, including nuclear, are part of a more cost-effective, cleaner generation mix. While the Southeast is projected to have approximately 100 GW of fossil resources – including 29 GW of new combined-cycle gas generation – online by 2040, the study also projects 27 GW of new nuclear capacity, 110 GW of new solar, and 30 GW of new storage capacity by 2040.
• Increased regional and inter-regional transmission utilization offers a critical and immediately available reliability benefit. More effective use of existing transmission and better coordination within the Southeast and with neighboring regions can enable the region to import about 7 GW by taking advantage of geographic diversity and sharing resources during challenging system conditions. Increased utilization of the existing transmission system also increases the value of solar and storage, enabling earlier additions of these resources.
• Flexible demand can further help address the Southeast’s resource adequacy challenges. Programs designed to respond during actual risk hours can provide broader value through longer-duration winter responses, overnight flexibility, and extended deployment during heatwaves. Shifting demand away from overnight risk hours during winter challenges and toward hours with greater solar production can reduce the need for firm resources by about 7 GW.
The report’s analysis points to the necessity of an “all of the above” approach to long-term planning, Brattle said.
"Beyond new resource development, more effective transmission utilization, regional trading – including non-firm energy trades – flexible demand, and improved performance of the existing fleet provide important and complementary reliability capabilities. Used together with the projected generation and storage additions, these strategies can address resource adequacy risks more comprehensively and cost-effectively than relying on a narrower set of solutions," Brattle said.
The report was authored by Brattle Principals Akarsh Sheilendranath, Johannes Pfeifenberger, and Michael Hagerty; Managing Energy Associate Wonjun Chang; Energy Specialist Sophie Edelman; and Senior Energy Analyst Tina Zhang.
