SPP’s RTO Expansion: A Major Milestone for U.S. Power Markets
Market Change Overview
Southwest Power Pool is preparing for one of the most significant market expansions in North America. On April 1, 2026, most Western Energy Imbalance Service participants will transition into the Integrated Marketplace, gaining access to full regional transmission organization services for the first time. Others may pursue participation in Markets+, coming in 2027, which provides RTO-like benefits without full RTO membership.
With FERC approval of SPP’s amended tariff, the expansion positions SPP as an RTO operating across both the Eastern and Western Interconnections. To support this structure, SPP is creating separate balancing authority areas for the East and West, allowing coordinated operations while maintaining requirements unique to each interconnection.
For WEIS participants that are transitioning, this move represents a shift from a real-time imbalance market into a full RTO framework that includes centralized unit commitment, day-ahead scheduling, co-optimized energy and reserves, transmission congestion rights processes, and expanded planning and reliability services. Existing SPP members will also adopt new workflows and system changes associated with the RTO West Expansion.
These updates introduce operational impacts across multiple business functions. Operations and real-time teams are preparing to adjust procedures to reflect the new East and West balancing authority areas and incorporate new DC Tie processes that are new under the West Expansion. Scheduling teams must align internal workflows with updated requirements for demand, load forecasts, and virtual offer submissions in addition to working with revised UI and integration pathways for Market and Reserve services. Settlement teams are adopting separate Market and Transmission settlement reports, update reconciliation processes, and incorporate new charge components and estimate logic into daily workflows. IT and integration teams need to validate updated APIs, WSDLs, and UI, load, and submit processes across all affected areas, and prepare systems for future changes to public data reports once technical specifications are released.
This expansion reflects SPP’s continued evolution and aims to support improved reliability, coordinated operations, and long-term economic efficiency across a broader regional footprint.
Hartigen’s Role
Hartigen is preparing PowerOptix to support all interface, settlement, and TCR updates introduced through SPP’s RTO Expansion. Enhancements include updated support across Market, Reserve, Virtual, Demand, DC Tie, and Notification services. Additional updates include API and WSDL updates across affected Market, Settlement, and TCR functions. PowerOptix will also include UI, load, and submit updates across all impacted areas, as well as new DC Tie functionality. Additional enhancements include improved workflows for reconciliation, validation, and downstream settlement processes, and calculation updates to support new estimate methodologies and required settlement components. These updates ensure customers are able to operate reliably and efficiently within the expanded Integrated Marketplace.
Important Milestones
Testing and certification activities have been completed or are currently underway.
TCR Go-Live: January 2, 2026
SPP RTO Expansion Go-Live: April 1, 2026
Key Takeaways
Most WEIS participants will join SPP’s Integrated Marketplace on April 1, 2026; others may transition to Markets+ in 2027.
Existing SPP members will also adopt new structures, BAAs, and interfaces introduced by the RTO West Expansion.
Settlement reporting is transitioning to separate Market and Transmission report services.
TCR services are updating APIs and WSDLs to support Western participation and mitigate operational risk.
Reference
Content in this edition reflects Hartigen’s internal expertise, with significant contributions from our SPP market expert, Megan Hlavinka. Thank you as well, Michael Canto and David Potts for your contributions.