The SunZia Transmission Line Project will be located in the USA. (Credit: © Pattern Energy)
The route of the project. (Credit: © Pattern Energy)
Construction commencement at the project site in Corona, New Mexico. (Credit: © Pattern Energy)
Groundbreaking of the SunZia Transmission Project. (Credit: © Pattern Energy)

SunZia Transmission is an under-construction ±525 kV high-voltage direct current (HVDC) transmission line in the US.

The transmission line will stretch from central New Mexico to south-central Arizona.

Renewable energy company Pattern Energy Group acquired the SunZia Transmission project from MMR Group-subsidiary SouthWestern Power Group in July 2022.

Once complete, SunZia Transmission will deliver renewable power generated by Pattern Energy’s 3,515MW SunZia Wind facility.

The transmission line will transport 3,000MW of electricity and will enable delivering power to around 3 million Americans.

Overall, the SunZia Wind Project and the transmission project are expected to deliver an economic benefit of around $20.5bn.

The US Department of the Interior’s Bureau of Land Management (BLM) approved the project in May 2023.

Pattern Energy Group reached financial close on the wind project and transmission line in December 2023.

The construction works also began in the same year. The project will create more than 2,000 construction jobs and over 100 permanent jobs.

SunZia Transmission is expected to be commissioned in 2026.

SunZia Transmission Project Route Details

The bipolar SunZia Transmission Project will stretch between Corona, New Mexico and Pinal County, Arizona in the US.

The 550-mile bi-directional HVDC transmission line will pass through federal, state, and private lands. Approximately 185 miles will be on federal lands, 227 miles on state land, and 142 miles will be located on private lands.

The Bureau of Land Management (BLM) Right-of-Way granted is 400ft wide to accommodate e the 500kV transmission line.


The construction of the transmission line will include one 500kV High Voltage Direct Current (HVDC) line of approximately 553-miles and two 500kV High Voltage Alternating Current (HVAC) line of approximately 1 mile length.

The project will also involve the construction of other ancillary facilities.

The transmission line components will include steel lattice, guyed mast structures, self supporting four-legged steel lattice structures, and self-supporting tubular pole structures.

The height of the structures will range from 100ft to 170ft and the distance between these structures would be typically 1,000 to 1,500ft, depending on topographical and site-specific conditions

SunZia Transmission Project Description

According to the Plan of Development (POD) June 2023, the transmission line route will originate at the proposed SunZia East Substation in Torrance County, New Mexico, and will terminate at the existing Pinal Central Substation in Pinal County, Arizona.

The transmission line will have four segments.

Segment 1 will stretch from the existing 500kV Alternating Current (AC) Pinal Central Substation to the new 500kV AC SunZia West and Converter Station and new 500kV AC Willow Substation.

The second segment will extend from the new 500kV AC Willow Substation to the new 500kV AC SunZia South Substation.

Third segment will be from new 500kV AC SunZia South Substation to the New Mexico Institute of Mining and Technology (New Mexico Tech) and the fourth will connect the New Mexico Tech to the new 500kV AC and Converter Station.

New access roads and existing roads will be required for construction, maintenance, and associated facilities of the project.

The SunZia Transmission Project is planned to be constructed in two phases.

Phase I includes the first nominal 500 kV circuit. The first transmission line will be a DC facility between the SunZia East and the SunZia West substations and an AC facility between SunZia West Substation and Pinal Central Substation.

In the first phase, SunZia East and SunZia West substations will be constructed.

Phase II of the project with second transmission line will be known as El Rio Sol. In this phase, the Willow and SunZia South substations will be constructed.

Both the phases will co-locate with the 115kV and 50 feet wide Tri-State (Phase I) and 345kV and 100 feet wide El Paso Electric (Phase 2) existing transmission lines passing north-south through the Sevilleta NWR.

The HVDC Light station in New Mexico will convert AC power to DC for transport in the overhead lines. The electricity will be reconverted to AC at the HVDC station in Arizona for integration into the receiving grid.


Pattern Energy Group closed an $11bn non-recourse financing for the SunZia project, including the wind and transmission components.

It included around $8.8bn in construction and term facilities and $2.25bn in tax equity.

Several banking institutions such as BNP Paribas, Crédit Agricole Corporate and Investment Bank and MUFG Bank among others acted as Initial Coordinating Lead Arrangers and Joint Bookrunners for construction and term facilities.

BNP Paribas, Crédit Agricole Corporate and Investment Bank, MUFG Bank, Societe Generale, and Sumitomo Mitsui Banking Corporation acted as co-syndication agents.

The tax equity term loan facility was provided by Banco Santander, and Santander Bank as Joint Coordinating Lead Arrangers.

Bank of America, GE Vernova’s Financial Services business, Natixis Corporate & Investment Banking and Royal Bank of Canada served as Joint Lead Arrangers.

Contractors Involved

Power Engineers prepared the Plan of Development (POD), published in June 2023, of the SunZia Transmission Project.

Quanta Infrastructure Services Group was selected by Pattern Energy as the engineering, procurement and construction (EPC) Contractor of the transmission line.

Hitachi Energy secured the contract to supply the HVDC technology including its HVDC Light technology and MACH digital control platform for the project.