SPP said Monday that six more Pacific Northwest entities are interested in participating in the next phase of the grid operator’s energy market services in the Western Interconnection.

The six organizations — Avista, Chelan County Public Utility District (Wash.), Grant County Public Utility District (Wash.), Puget Sound Energy, Tacoma Power and Canadian marketer Powerex — made their intentions public in an Aug. 19 letter to SPP, saying they intend to work with the RTO to develop a Western market that “supports reliability and delivers value to our customers.”

They join Bonneville Power Administration in formally committing to funding the further development of Markets+, a conceptual bundle of services that would centralize day-ahead and real-time unit commitment and dispatch and provide hurdle-free transmission service. Markets+ has been framed as a voluntary, incremental opportunity to realize market benefits by utilities that aren’t ready to pursue full RTO membership. (See BPA Commits to Funding Markets+ Development.)

SPP said the seven entities willing to move forward with the development of Markets+ represent a “well connected footprint with extensive transmission capability, a large fleet of clean flexible hydro resources and a peak load” of over 30 GW. That is 50% larger than ISO-NE, the nation’s smallest grid operator, it said.

“We are very encouraged by the governance and market design progress for Markets+ over the past several months, which has been achieved through SPP’s collaborative, stakeholder-driven approach,” Powerex CEO Tom Bechard said in a statement.

Powerex Managing Director Mark Holman has been one of the most vocal and inquisitive participants in SPP’s Markets+ development sessions, which began late last year. The grid operator has held three in-person meetings with Western stakeholders to review work on the market’s service offering and discuss outstanding items and next steps. (See SPP Continues to Build on Markets+ Offering.)

“By participating in this process, we are working together to build Markets+ on a strong foundation of input from Western stakeholders, ensuring the market meets the needs of the West and brings value to all participants,” SPP CEO Barbara Sugg said.

A draft service offering that explains how the proposed service will address governance structure, market design, transmission availability and other items will be distributed Sept. 30, setting off a public comment period. The final service offering will be distributed Nov. 18. Interested parties will make a commitment to fund further market development in early 2023.