Construction of the final segment of the Southwest Intertie Project, a 576-mile transmission corridor connecting an area from Idaho to just south of Las Vegas, Nevada, is underway. Officials celebrated the latest milestone for the installation during a groundbreaking ceremony in Ely, Nevada, on September 3.
LS Power, through its affiliate Great Basin Transmission, marked the start of work on the Southwest Intertie Project-North (SWIP-North) on Thursday. The SWIP-North, which is expected to enter operation in 2028, will be a 285-mile, 500-kilovolt (kV) transmission line connecting the Midpoint Substation near Twin Falls, Idaho, with the Robinson Summit Substation near Ely. LS Power said the project represents an investment of more than $1 billion in power infrastructure “that will help strengthen grid reliability, reduce congestion and expand access to diverse power supply resources across the West.”
“Reliable power increasingly depends on our ability to move electricity across regions, and that requires major investment in transmission,” said LS Power CEO Paul Segal. “SWIP-North will complete an important new pathway between the Pacific Northwest and the Desert Southwest, improving reliability and giving the Western grid greater flexibility. Projects of this scale take persistence, and we’re proud to have spent more than two decades advancing this corridor to construction.”
Idaho to Southern Nevada
The entire Southwest Intertie Project once complete will connect Idaho’s Magic Valley to Nevada’s Eldorado Valley south of Las Vegas. The SWIP-North segment, more than 70% of which will be located in Nevada, joins two earlier phases of the overall project developed by LS Power. Those include the 231-mile One Nevada Transmission Line (ON Line), built in partnership with NV Energy and placed into service in 2014, and the 60-mile DesertLink Line, which began delivering power in 2020. The transmission paths connect to the California Independent System Operator (CAISO) grid.
“Construction of this last phase of the Southwest Intertie Project underscores Nevada’s position as a strategic energy hub for the West,” said Nevada Gov. Joe Lombardo. “SWIP-North will provide benefits for Nevadans, including additional transmission capacity, new energy import and export opportunities, increased energy reliability for residents and businesses, and enhanced resiliency against extreme weather events and wildfires.”
Officials on Thursday said that once the SWIP-North segment is energized the entire Southwest Intertie Project will have the ability to move more than 2 GW of bidirectional electricity across the regional grid. That capacity includes 500 MW of northbound transmission dedicated for Idaho Power customers.
“SWIP-North represents a unique cooperation between multiple regions, states and utilities—and a great example of innovation and collaboration between a private developer, LS Power; Western electric utilities, NV Energy and Idaho Power; and a regional grid operator, the California ISO, to balance cost allocation, capacity sharing and benefits,” said LS Power President Paul Thessen.
Shared Capacity Rights
NV Energy, Idaho Power, and CAISO all will share capacity rights on the line. The capacity agreement between NV Energy and LS Power affiliates stipulates that NV Energy covers all costs for the ON Line; LS Power covers all costs for SWIP-North; and both share capacity across the full path. LS Power has assigned its capacity rights to CAISO and Idaho Power.
Elliot Mainzer, CEO and president of CAISO, said, “Major transmission investments like SWIP-North are essential to building a more reliable, resilient and efficient Western grid. By creating a stronger connection across the West, this line will give grid operators greater flexibility to move power where it is needed most, improve access to diverse energy resources, and enhance our ability to respond to changing system conditions and extreme weather events.”
Mitch Colburn, Idaho Power vice president of Planning, Engineering and Construction, said, “Keeping energy costs affordable for our customers is one of our top priorities. SWIP-North will help Idaho Power meet growing energy demands and reduce costs for our customers by connecting Idaho Power to the Desert Southwest’s low-cost energy resources.”
Great Basin Transmission was selected by CAISO in 2023 to develop, permit, finance, construct, own, operate, and maintain the SWIP-North Project, with final cost recovery approval in 2024. Idaho Power obtained approval for participation in the project in 2025.
“Beyond the increased electrical capacity that the project will bring to the Western grid, SWIP-North will bring measurable economic benefits to Nevada and Idaho during construction and beyond,” said Mark Milburn, LS Power senior vice president of Development. “We estimate the project will add around 300 construction jobs, generate over $375 million in regional economic impact from construction-related activity and provide millions in property tax revenue each year to help fund essential local services.”
—Darrell Proctor is a senior editor for POWER.
