CAISO’s Western Energy Imbalance Market notched another milestone last week as it welcomed the country’s largest municipal utility and extended its eastern border to include much of New Mexico.

The Los Angeles Department of Water and Power (LADWP) and Public Service Company of New Mexico (PNM) both commenced trading in the EIM on April 1, coming a week after four publicly owned utilities became participants, including Turlock Irrigation District (TID) and Balancing Area of Northern California members Modesto Irrigation District (MID), City of Redding and Western Area Power Administration-Sierra Nevada Region.

The EIM will grow to 15 members next month with the addition of Montana-based NorthWestern Energy. This spring’s expansion represents the largest ever for the market, which began operations in November 2014 with PacifiCorp as its first member.

“We are very pleased to welcome LADWP and PNM as new participants in the Western EIM,” CAISO CEO Elliot Mainzer said in a statement. “We look forward to working with both utilities to bring additional economic and environmental benefits to their customers as we further expand the geographical scope of the real-time energy market.”

LADWP brings significant and wide-ranging transmission assets into the EIM. The utility owns and operates more than 3,600 miles of transmission lines crossing five states, including half of the 3,100-MW Pacific DC Intertie linking the L.A. metro area with the Bonneville Power Administration territory in the Pacific Northwest.

Other transmission assets include 60% of the contract capacity rights on the Southern Transmission System line connecting Southern California with the Intermountain Power Plant (IPP) in Utah, a 36% ownership stake in the Mead-Adelanto Transmission Project connected to Nevada, and co-ownership of the Navajo-McCullough Transmission Line between the now-retired Navajo Generating Station in Arizona and the McCullough substation in Nevada.

LADWP also controls about 8,000 MW of generating capacity, including the 1,900 MW coal-fired IPP (slated for conversion to an 840-MW gas-fired plant in 2025), 15% of the output from the 2,080-MW Hoover Dam in Nevada, and 5.7% of output from the 3,300-MW Palo Verde nuclear generating station in Arizona.

The utility’s participation in the EIM will be “a win-win proposition for the City of Los Angeles and the Western Grid in terms of fostering the integration of renewable energy while maintaining power reliability, as the City of Los Angeles moves ahead with our goal of 100% renewables as well as assisting all California utilities in meeting the state target of 60% renewables by 2030,” said Reiko Kerr, LADWP senior assistant general manager of power system engineering, planning and technical services.

PNM, BANC, TID

PNM operates 3,189 miles of transmission, including a 500-kV segment from the Palo Verde plant (of which it controls 402 MW of output) and a 345-kV backbone spanning New Mexico and capable of delivering power from the wind-rich eastern reaches of the state to the Four Corners delivery point in the northwest. A portion of the 345-kV line extends into SPP.

The utility owns 2,865 MW of generating capacity, including the coal-fired San Juan Generating Station (847 MW) and Four Corners plant (200 MW). It also has more than 300 MW of wind assets and nearly 120 MW of solar.

PNM’s participation in the EIM will also include the loads of 11 members of wholesale power cooperative Tri-State Generation and Transmission Association, which in February transitioned a number of its Colorado, Nebraska and Wyoming members to join SPP’s newly launched Western Energy Imbalance Service. (See WEIS Market ‘First Step’ to Full RTO Membership.)

“PNM, CAISO and Tri-State’s close collaboration enabled us to have a smooth entry into the [EIM],” Tri-State CEO Duane Highley said in a statement. “We greatly appreciate the professionalism of the PNM and CAISO staff, who we worked with over many months to enter the market.”

The engagement of MID, Redding and WAPA-Sierra Nevada boosts the roster of BANC participants in the EIM. The group’s largest member, Sacramento Municipal Utility District, joined in April 2016. (See SMUD Goes Live in Western EIM.) BANC members Roseville Electric Utility, City of Shasta Lake and Trinity Public Utilities District have not yet committed.

Like BANC, TID owns a share of the California-Oregon Intertie (COI), the other major transmission line that allows California to tap the Northwest’s hydroelectric resources. TID’s transmission network also links to CAISO at two locations and to the SMUD and WAPA systems at the Tracy substation, the tie-in for the COI.

TID’s generation portfolio includes a 136-MW share of the output from the Don Pedro Dam, the 136-MW Tuolumne Wind Project, nearly 100 MW of gas-fired generation and a 6.8-MW geothermal plant.

“As participants in the EIM, we have the opportunity to further capitalize on the generation infrastructure TID has developed over the years,” TID General Manager Michelle Reimers said.