Southwest Power Pool Can Cost-Effectively Maintain Resource Adequacy Over Next Decades, Brattle Study Shows
In a new report prepared for Southwest Power Pool (SPP), Brattle experts found that SPP is well positioned to meet long-term investment and resource adequacy challenges as the regional electricity markets navigate high load growth and a changing generation fleet. This Future Energy & Resource Needs Study (FERNS) is part of SPP’s strategic initiative to proactively assess how energy supply costs and year-round reliability and resiliency requirements are expected to change over the next decades.
SPP already generates 47% of its electricity from carbon-free resources, but this share of carbon-free generation is projected to increase as load growth accelerates and the region will make substantial generation and transmission investments to maintain grid reliability. The Brattle team simulated optimal generation and transmission expansion over the next 25 years (through 2050) while considering various reliability challenges, such as during extreme seasonal weather events, renewable droughts, and weather-related generation outages.
The report’s key takeaways include:
- Even in scenarios with high load growth and high shares of renewable generation, SPP is projected to be able to maintain resource adequacy in a cost-effective and affordable fashion through a combination of retaining existing generation capacity and the addition of new resources, including storage.
- A projected $88–$263 billion of generation investments will be needed to support SPP’s load growth through 2050. Due to the high load growth, this is possible without significant rate increases (in inflation-adjusted terms), especially if federal tax credits (or similar policies) remain available. In scenarios without tax credits, region-wide investments are around $80 billion lower over the next 25 years and SPP’s average generation and transmission costs are about $10/MWh higher (in 2023 dollars).
- Between 70% and 90% of SPP’s annual energy will likely be generated from emissions-free resources by 2050 (depending on the availability of tax credits), with conventional generation continuing to meet a disproportional share of SPP’s resource adequacy needs. These results are a function of trends in technology costs, natural gas prices, and the availability of tax credits (or similar policies).
- Solar is projected to outcompete wind: 20–48 GW of projected investment in new wind generation compares to 42–130 GW of new solar additions by 2050. As solar generation expands, 22–59 GW of cost-effective battery storage is projected to be built (and often co-located) to maintain resource adequacy.
- Over the next 25 years, 4–21 GW of new regional transmission capacity (between SPP zones) is projected to be needed and cost-effective to support the delivery of generation to load centers.
- The nature of resource adequacy challenges will change significantly during the 2030s, with scarcity events (a) growing more frequent during winter months (particularly in high electrification futures) and (b) shifting from afternoon peak load hours into the early evening hours (after sunset). Winter planning reserve margins will need to be significantly higher than summer reserve margins.
- The effective load carrying capability (ELCC) value of solar and short-duration storage resources is projected to decline over time, while that of wind resources increases. Even the ELCC of 8‑hour storage declines in the high renewable generation scenarios, indicating a need for long-duration storage. Throughout the study period, interties with neighboring regions offer valuable resource adequacy and extreme-weather resilience benefits to the SPP footprint.
- SPP has sufficient available land to accommodate the projected 60–180 GW of wind and solar additions through 2050 in all scenarios evaluated.
The report, “Future Energy & Resource Needs Study (FERNS),” was prepared for SPP by Principal Johannes Pfeifenberger, Energy Research Associates Kate Peters and Sam Willett, Senior Energy Analyst Paige Vincent, and Energy Analyst Hazel Ethier.
SPP staff presented a summary of the FERNS report during the March 18, 2025 joint meeting of SPP’s Consolidated Planning Process Task force (CPPTF), the Economic Studies Working Group (ESWG), and the Transmission Working Group (TWG). The materials for this meeting, including the SPP staff presentation, are posted here. Brattle slides from an earlier FERNS update to SPP stakeholders are posted here and here. View press coverage of the report here.
