NorthWestern Energy to Participate in Regional Transmission Projects

NorthWestern Energy Group, Inc. d/b/a NorthWestern Energy (Nasdaq: NWE) is joining new high voltage transmission projects to expand Montana’s grid, meet the state’s increasing energy demand, enhance energy security and create opportunities to serve regional energy needs that will benefit all of our customers.

NorthWestern Energy joins North Plains Connector east-west transmission line

NorthWestern Energy has signed a nonbinding memorandum of understanding with North Plains Connector LLC, a wholly owned entity of Grid United, to own 10% (300 megawatts) of North Plains Connector, a 3,000-megawatt, 420-mile high-voltage direct current (HVDC) transmission line to be constructed with endpoints near Bismarck, North Dakota, and Colstrip, Montana. Grid United and ALLETE, Inc. are jointly developing North Plains Connector. Avista, Portland General Electric and Puget Sound Energy also have ownership MOUs with North Plains Connector. The project is entering the permitting phase and initiating regulatory filings with approvals targeted in 2026. Construction is expected to commence in 2028, aiming for the project to be operational by 2032. Under the terms of the memorandum of understanding, Grid United will continue to fund the development of North Plains Connector. NorthWestern Energy would invest when project regulatory approvals and permits are in place.

“NorthWestern Energy’s Colstrip, Montana substation is strategically located and will serve as a critical endpoint for North Plains Connector, reinforcing Colstrip’s position as an essential energy hub,” said NorthWestern Energy President and CEO Brian Bird. “The North Plains Connector developer’s collaborative approach with Montana communities to address concerns and ensure the footprint reflects local priorities aligns with NorthWestern Energy’s commitment to our customers.”

North Plains Connector is the first interregional transmission line to create a major grid-to-grid connection across the three energy markets, the Midcontinent Independent System Operator (MISO), Southwest Power Pool (SPP), and Western Electricity Coordinating Council (WECC). The transmission line will create connection between NorthWestern Energy’s Montana and South Dakota service areas. The bidirectional transmission line will efficiently transport large amounts of power from areas with supply to areas in need and take advantage of diverse load and weather patterns.

“NorthWestern Energy is the only partner serving customers in both regions, which have diverse energy load demands and diverse energy generation resources,” said Bird.

“We are pleased to welcome NorthWestern Energy to North Plains Connector,” said Michael Skelly, CEO and co-founder of Grid United. “As Montana’s largest energy provider, NorthWestern Energy brings a breadth of experience and deep understanding of the region’s energy needs. Their support reinforces the importance of North Plains Connector as a meaningful solution for a strong and reliable electric grid.”

Earlier this year, NorthWestern Energy supported the Montana Department of Commerce as part of the North Plains Connector Interregional Innovation (NPCII) consortium in its successful application for a $700 million grant from the U.S. Department of Energy’s Grid Resilience and Innovation Partnership (GRIP) program. The NPCII includes an upgrade of the Colstrip Transmission System and while the majority of the grant is earmarked for the North Plains Connector, the grant also includes funding for a potential upgrade of the Colstrip Transmission System, which is jointly owned and operated by NorthWestern Energy.

Montana to the South Transmission Corridor

NorthWestern Energy and Grid United have also entered into a letter of intent to continue transmission development to further enhance the grid through the southwest corridor of Montana. Development to expand the southwest corridor of Montana through grid buildout would represent a significant step in enhancing connectivity between Montana and the broader Western energy market - bolstering grid reliability, allowing for critical import capability and enabling customers to access and benefit from emerging energy markets in the West.

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NorthWestern Energy - Delivering a Bright Future

NorthWestern Energy Group, Inc., doing business as NorthWestern Energy, provides essential energy infrastructure and valuable services that enrich lives and empower communities while serving as long-term partners to our customers and communities. We work to deliver safe, reliable, and innovative energy solutions that create value for customers, communities, employees, and investors. We do this by providing low-cost and reliable service performed by highly-adaptable and skilled employees. We provide electricity and / or natural gas to approximately 775,300 customers in Montana, South Dakota, Nebraska, and Yellowstone National Park. Our operations in Montana and Yellowstone National Park are conducted through our subsidiary, NW Corp, and our operations in South Dakota and Nebraska are conducted through our subsidiary, NWE Public Service. We have provided service in South Dakota and Nebraska since 1923 and in Montana since 2002.

About Grid United

Grid United is an independent transmission company aiming to modernize the United States' power grid to create a more resilient and efficient electric system that uses the nation's abundant and geographically diverse natural resources to the benefit of all consumers. For more information, visit www.gridunited.com.

About ALLETE

ALLETE, Inc. (NYSE: ALE) is an energy company headquartered in Duluth, Minnesota. In addition to its electric utilities, Minnesota Power and Superior Water, Light and Power of Wisconsin, ALLETE owns ALLETE Clean Energy, based in Duluth; BNI Energy in Bismarck, North Dakota; and New Energy Equity, headquartered in Annapolis, Maryland; and has an 8% equity interest in the American Transmission Co. More information about ALLETE is available at www.allete.com.

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NorthWestern Energy Investor Relations Contact: Travis Meyer [phone] [e-mail]

Media Contact: Jo Dee Black [phone] [e-mail]

Grid United Media contact: Ashley McGeary, Communications Director [e-mail]

ALLETE, Inc. Media Contact: Amy Rutledge 218-723-7400 [e-mail]