The seam between America’s two largest power grids is starting to close.
On August 28, the Department of Energy and the Montana Department of Environmental Quality released the final environmental impact statement for the North Plains Connector. The project is a proposed 422-mile, 525-kilovolt high-voltage direct current line that would run from Colstrip, Montana, to St. Anthony, North Dakota. The two agencies led the review jointly.
According to DOE, the line would give the Western and Eastern Interconnections 3,000 megawatts of bidirectional transfer capability. Power could flow either way, depending on which side of the country needs it more.
An environmental impact statement does not put steel in the ground. It does clear the biggest federal hurdle a long-distance line faces before construction, and for interregional transmission in the United States, that hurdle has stopped many projects.
The Grid Seam Is Where Reliability Gets Tested
The United States runs its power system as separate interconnections, and only limited capacity links them. When extreme heat or cold hits one region, help from the other side is limited by how much transfer capacity exists between them.
DOE says the North Plains Connector is designed to increase transfer capacity and open up access to generation, so it can meet growing electricity demand in Montana and North Dakota and across the country. The department also says linking the grids would strengthen regional reliability and resilience and help protect against outages.
Catherine Jereza, Assistant Secretary for the Office of Electricity, said connecting the nation’s eastern and western power grids is a critical step toward ensuring long-term energy affordability and reliability for millions of Americans.
The line also crosses more than a geographic boundary. Puget Sound Energy describes it as the first transmission link connecting the Midcontinent Independent System Operator, the Western Electricity Coordinating Council and the Southwest Power Pool. Those three regions have different market rules, planning processes and resource mixes.
Value comes from that diversity.
A Federal Review That Kept Moving
The schedule stands out. According to Puget Sound Energy, the project entered the National Environmental Policy Act process in October 2024. DOE published the draft environmental impact statement in January 2026 and opened a 45-day comment period. The final document reflects that public feedback, along with route and construction refinements made by the developer, the department says.
Oklahoma Energy Today reported that the federal review finished well under the two-year maximum timeline. For a line that crosses two states, three regional systems and the boundary between interconnections, that pace is unusual.
Developers have long argued that permitting, more than engineering or capital, keeps interregional lines from getting built. The North Plains Connector review suggests that a large HVDC project can get through federal environmental review on a predictable schedule when the agencies and the developer keep it moving.
That precedent matters well beyond Montana.
Utilities Committed Before the Permits Arrived
Grid United and ALLETE are developing the project jointly, according to Puget Sound Energy. When DOE awarded the project a $700 million grant through its Grid Resilience and Innovation Partnerships program in August 2024, Montana Free Press reported that ALLETE held a 35 percent development share and Portland General Electric had reserved a 20 percent capacity share. The project was then estimated at $3.6 billion.
Puget Sound Energy signed on in December 2024 for 750 megawatts, the largest share of any participating utility. Its commitment is a non-binding memorandum of understanding, and the utility will invest once regulatory approvals and permits are in place. Josh Jacobs, the utility’s vice president of clean energy strategy and planning, called the line “a critical link connecting PSE and its customers to new markets that can provide needed resource diversity.”
So the demand came first, and the permits are now catching up.
Few interregional proposals reach final federal review with this kind of backing. Utilities from the Pacific Northwest to the Upper Midwest have reserved capacity on a line that does not exist yet, which signals how much they value access to resources outside their own region.
What the Milestone Means Across the Market
The final environmental review changes the planning assumptions for several groups at once:
- Generation developers in Montana and North Dakota gain a credible path to buyers in both interconnections.
- Western utilities gain access to Plains resources whose output often peaks at different times from their own.
- Grid operators in MISO, SPP and WECC will need coordination rules for scheduling a large controllable HVDC flow.
- Investors get a reference case for how an interregional HVDC line moves through federal environmental review.
- Communities along the route stand to benefit from the $46 million that Montana Free Press reported for roads, sewer and water services.
- Regulators can draw on the rate impact study published as an appendix to the final statement.
Direct current matters here. An HVDC line lets operators set the amount and direction of power flow, so it behaves less like a passive wire and more like a dispatchable asset. That lets planners treat the connection as a reliability resource in its own right.
The Real Work Begins After the Review
The remaining federal and state approvals, final financing and procurement all lie ahead. Puget Sound Energy has pointed to 2032 as the anticipated in-service date. Before then, the developers will have to secure converter stations and HVDC equipment from a supply chain that is already busy with offshore wind, data center and international transmission orders.
Construction will test the same coordination that got the project through review: landowners, tribal and local governments, two state governments and a group of utilities with their own regulators and customers.
Execution is now what counts.
The North Plains Connector will not solve the country’s interregional transmission shortfall by itself. It does show the order in which such a project can come together: utilities commit capacity, federal funding narrows the cost gap, and environmental review finishes on schedule. Other interregional proposals now have that model to follow.
For decades, the line between America’s grids has been treated as a fixed fact of geography. The North Plains Connector is testing whether it can become a market instead.
