Powering Energy Highways: Minnesota’s transmission progress
Over the past several years, CUB has sought to keep Minnesotans informed of transmission buildouts across the state. As captured in our previous articles, transmission “highways” play a pivotal role in transporting electricity from where it is produced to where it is used. Additional transmission capacity is needed to meet rising energy demand, increase system reliability, and support the integration of renewable energy resources onto the grid. Many of the projects discussed in our previous articles have now been approved for construction or are nearing the end of the regulatory review process. Below, we provide a brief update about the status of these “energy highways.”
The Regulatory Process
When a utility or developer wants to build a transmission line, they must first seek approval from the Public Utilities Commission (PUC). During the review process, the PUC must find both that the line is needed and that the location of the line is reasonable.
In evaluating whether to grant a “certificate of need” for a transmission line, the PUC must look at how the proposed project relates to the current and future energy needs of the state. This requires considering numerous factors, including how the transmission line contributes to the adequacy and reliability of energy supplies, whether there are reasonable alternatives to the project, and whether the line is expected to have socioeconomic or environmental impacts.
If the PUC determines a transmission line is needed, then it must also approve route permits that identify where the project will be built. State agencies play a major role in reviewing proposed transmission routes to ensure impacts to the environment and local communities are minimized. Hearings are also conducted to receive feedback from the public and landowners that might be affected by project construction.
Minnesota Transmission Projects Currently Underway
The below list does not include every transmission line currently being built or undergoing regulatory review. Except for the Minnesota Energy Connection line, the projects discussed below are part of a broad portfolio of transmission lines developed by the Midcontinent Independent System Operator (MISO) called “Tranche 1.”
MISO is a nonprofit organization that oversees the electric grid across 15 states—including Minnesota—and Manitoba. In that role, MISO is tasked with managing energy supply and demand to ensure that customers’ electricity needs are reliably met. Tranche 1 involves building 18 new transmission lines across the Midwest region—including four in Minnesota—to revitalize the aging electric grid and keep up with changing energy needs. As a complete portfolio, Tranche 1 is expected to produce approximately $37 billion in benefits over the next 20 years, with many of these cost savings being realized by Minnesota ratepayers.
Big Stone South – Alexandria – Big Oaks
Partially Approved, Under Review
Dockets Nos. CN-22-538; TL-23-159; TL-23-160
The Big Stone South project is expected to increase reliability and enable abundant wind energy from the Dakotas to flow into Minnesota. The buildout of renewable resources enabled by this project could provide up to $2.1 billion in energy savings over the first 20 years of operation.
The PUC granted a certificate of need for the Big Stone South – Alexandria – Big Oaks transmission line in October 2024. A route permit was also approved for the eastern segment of the transmission line, which extends eastward from Alexandria, Minnesota to Sherburne County. This portion of the project is expected to be completed in 2028. Various compliance filings were submitted through the first quarter of 2025, after which pre-construction efforts began in March.
The route for the western segment—which connects Big Stone City, South Dakota to a substation in Alexandria—is still undergoing regulatory review through a contested case process. Parties will submit testimony in August and September, after which an evidentiary hearing will be held. Public commenters can share their perspectives on the proposed route through October 20, 2025. The judge overseeing the case is expected to issue a report and recommendation by mid-February, 2026, after which the PUC will hold a hearing on the matter. This portion of the project is not expected to go online until 2030.
Iron Range – Benton County – Big Oaks (Northland Reliability)
Approved
Dockets Nos. CN-22-416; TL-22-415
The Northland Reliability project is designed to increase grid stability by providing better access to lower-cost wind resources and facilitating the reliable transfer of electricity to northern Minnesota on cold winter days. The line will allow existing coal facilities to cease operations and enable new carbon-free resources to come online. After construction, the transmission line is expected to provide up to $304 million in annual cost savings.
The Northland Reliability transmission line was approved by the PUC in February 2025. The project spans from the Iron Range to Benton County and replaces two lines between Benton and Sherburne counties. Approximately 85 percent of the project is located on existing rights of way. Vegetation surrounding the Benton County substation was removed starting in April 2025 to make way for further construction activities. The project is expected to be placed in service by mid-2030.
Mankato – Mississippi River
Under Review
Dockets Nos. CN-22-532; TL-23-157
The Mankato – Mississippi line will lower transmission congestion and allow more carbon-free energy resources to be added to the grid. In turn, the project will contribute to reducing carbon emissions by 2.4 to 5.3 million metric tons over the first 20 years of operation. By providing additional transmission capacity, the line will also relieve concerns about “overloading,” which occurs when the amount of electricity flowing onto the grid exceeds what transmission infrastructure is capable of handling.
The Mankato – Mississippi River project connects substations in Wilmarth, Faribault, and Rochester before heading east to the Mississippi River. Several substations are also expected to be upgraded. The transmission line is still undergoing regulatory review, with parties commenting on the need for the project during the first quarter of 2025.
The proposed route is undergoing a contested case process. Parties will file testimony over the next several weeks, and public hearings will be held between May 27-29. Comments can be submitted in the docket until June 10, 2025. The judge overseeing the case is expected to provide a report and recommendation in October, after which the PUC will hold a hearing on the matter. If approved, the project is expected to be placed in service by 2030.
Minnesota Energy Connection Project
Approved
Docket Nos. CN-22-131; TL-22-132
While not part of Tranche 1, the Minnesota Energy Connection Project plays an important role in enabling Xcel’s transition to carbon-free energy resources. Every few years, utilities are required to file forward-looking integrated resource plans (IRPs) that explain how they will generate or procure electricity to meet their customers’ needs. As part of this process, the PUC approved Xcel’s proposal to retire its coal generation facility located in Sherburne County and reuse existing interconnection rights to put new wind and solar resources onto the grid. The Minnesota Energy Connection Project will help facilitate the transfer of that electricity and aid Xcel in its pursuit of cleaner, less carbon-intensive energy resources.
At a hearing on April 10, 2025, the PUC approved the Minnesota Energy Connection transmission line, which is designed to connect Xcel Energy’s Sherburne County substation in Becker, Minnesota to a new substation in Lyon County. The PUC’s written order has not yet been filed, but soon Xcel will start preparing pre-construction compliance documents in anticipation of beginning development. The transmission line is anticipated to go online in the second half of 2027, with new substation construction being completed in 2031.
Conclusion
The Minnesota PUC has made major strides towards modernizing the electric grid by approving recent transmission projects. These infrastructure improvements will bolster system reliability and expand access to lower-cost, carbon free energy resources.
As mentioned above, comment periods are currently open for the Mankato – Mississippi transmission line and the western portion of Big Stone South. If you are interested in providing comments on either of the projects, you can do so via the PUC website. Make sure to reference the individual docket numbers (listed above) for which you are providing comments. Your submission will become part of the public record for the proceeding.
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