SPP Becomes First RTO to Operate in Both Eastern and Western Interconnections with FERC Tariff Approval

Southwest Power Pool (SPP) has made history by becoming the first regional transmission organization (RTO) in the U.S. to operate across both the Eastern and Western Interconnections of the national power grid. On March 20, the Federal Energy Regulatory Commission (FERC) approved an amended tariff allowing SPP expansion into the Western Interconnection. This approval will enable seven Western entities to join SPP’s integrated marketplace starting in April 2026.

FERC Approval Opens the Door for Expansion

The amended tariff allows Western entities such as Basin Electric Power Cooperative, Colorado Springs Utilities, and Tri-State Generation and Transmission Association to expand their participation in SPP’s services. These entities currently participate in SPP’s Western Energy Imbalance Service (WEIS) market. As part of the expansion, they will also participate in the Integrated Marketplace, transmission planning, and reliability coordination.

SPP’s president and CEO, Barbara Sugg, expressed excitement over the approval. She said, “Expanding the RTO into the Western Interconnection is an exciting step in SPP’s growth.” She added, “It will bring value to new and existing members while enhancing reliability in both interconnections.” The expansion is a key milestone in SPP’s Aspire 2026 plan. This plan outlines how the RTO will fully integrate Western facilities into its market system, creating value for all members.

Western Expansion Enhances Reliability and Reduces Costs

Tri-State Generation and Transmission Association CEO Duane Highley highlighted the benefits of the expansion. “The Western expansion of the SPP RTO enhances reliability and resiliency for our members,” he said. “It helps us grow and diversify our resource portfolio while reducing emissions.” SPP offers advantages like efficient regional transmission planning and a participatory governance model. These features help reduce costs for members.

Similarly, MEAN’s Director of Wholesale Operations Brad Hans pointed out how the expansion will help reduce carbon footprints. “SPP’s RTO expansion into the Western Interconnect helps us reduce our carbon footprint,” he said. “It does so by maximizing renewable energy resources through economic dispatch.”

SPP Strengthens Its Presence in the West

As SPP moves toward the 2026 expansion, it is also developing Markets+, a new market designed to bring more value to the Western Interconnection. The Markets+ tariff was approved by FERC in January. It will allow SPP to operate two markets and manage the Western Resource Adequacy Program (WRAP). SPP believes that multiple markets will maximize value for participants and drive affordability, reliability, equity, and sustainability.

Sugg emphasized the importance of these upcoming markets. “With the expansion of the RTO’s Integrated Marketplace in 2026 and the launch of Markets+ in 2027, we look forward to bringing more value to the West,” she said.

SPP’s Journey and Future Outlook

Since earning FERC approval as an RTO in 2004, SPP has expanded rapidly. It has grown its service territory in the Eastern Interconnection from eight to 14 states. With the Western expansion, SPP will cover parts of 17 states. The official launch of the expansion is scheduled for April 1, 2026.