Regulatory approval for SunZia Transmission paves the way for a Southwest renewable energy corridor


Pattern Energy Group, a renewable energy developer, announced its SunZia Transmission project received the approval of the Arizona Corporation Commission (ACC) to build a 550-mile high voltage direct current transmission line from New Mexico to Arizona.

On Monday, the company’s Certificate of Environmental Compatibility application for the transmission project received the approval of the ACC. Separately, the New Mexico Public Regulatory Commission issued two unanimous approvals of Pattern Energy’s SunZia Wind project, a 3.5 GW proposed wind project in Torrance, Lincoln and San Miguel Counties, New Mexico to provide power across the transmission line to Pinal County, Arizona.

The power transmission project is on track for construction by mid-2023 and still requires state approval from the New Mexico PRC as well as federal approval from the Bureau of Land Management (BLM), expected by April 2023. It also needs approvals from local jurisdictions and stakeholder groups. According to a BLM filing, the project has involved cooperation from ten federal agencies, five state agencies and nine local authorities.

Once completed, the 525-Volt SunZia Transmission and Wind project represents the largest clean energy project in the U.S., including $8 billion in total investments, providing power from central New Mexico to more than 3 million residents of central Arizona.

“We are excited to get to work on the revolutionary SunZia Transmission line which will be the conduit for the largest wind project in U.S. history,” said Mike Garland, chief executive officer of Pattern Energy. “Once complete these projects will combine to increase the reliability of the western grid, create good jobs, and bring millions of dollars in economic benefits to Arizona and New Mexico.”

First approved in 2015, SunZia Transmission’s route was adjusted over the years as the result of planning with the Department of Defense and White Sands Missile Range. The project’s current path runs parallel to existing HVDC power line, Western Spirit Transmission line, for about 35 miles in order to minimize the environmental impact along the route for the new wind development.

The transmission line originates at a planned substation in near Corona, New Mexico, and traverses eight counties in New Mexico and Arizona before terminating at an existing substation in Casa Grande, Arizona, about 60 miles from downtown Phoenix and Tucson, Arizona.

Following publication on November 15, Pattern Energy spokesman Matt Dallas told this news publication, “SunZia will be a FERC open access transmission line so it would be available for other generators to utilize as with any other open access transmission network. Because it is an HVDC line, the costs and complexities associated with interconnecting along the route may be a challenge,” he said, while pointing to a second transmission line approved by the ACC that will run parallel to SunZia, providing an easier access point for other generation sources such as solar to interconnect with the local grid.

Southwestern Power, operated by MMR Group, is the owner of the second 500 kV high voltage-alternating current (HVAC) transmission line, El Rio Sol Transmission, a 550-mile transmission line that will run parallel to SunZia.  In July, Southwestern Power sold the SunZia transmission line to Pattern Energy in a sale transaction.

Southwest Renewable Resources

According to the Solar Energy Industries Association (SEIA), Arizona and New Mexico rank fifth and 18th in the U.S. for solar deployments, with 5.3 GW and 4.4 GW of respective development pipelines for the next five years.

The Southwest market represents a critical area for new HVDC and AC power transmission develop to bring multiple gigawatts of clean energy into markets such as Phoenix, Tucson and Albuquerque, N.M.


SunZia Transmission proposed route through Arizona and New Mexico.

Image: Pattern Energy

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