BLACK HILLS CORP /SD/

Pending Merger with NorthWestern

On August 18, 2025, we entered into the Merger Agreement with NorthWestern and Merger Sub. See Note 17 of the Notes to Consolidated Financial Statements in this Annual Report on Form 10-K for further discussion about the pending Merger.

One Big Beautiful Bill Act

See Note 15 of the Notes to Consolidated Financial Statements in this Annual Report on Form 10-K for discussion surrounding the OBBBA.

Trade Tariffs

Trade tariffs have been enacted over the last several months through presidential executive orders affecting products exported by several U.S. trading partners, and retaliatory tariffs have been imposed by some of these trading partners. While some tariffs scheduled to take effect were temporarily suspended, broad tariffs remain in effect with the possibility of additional tariffs being imposed. We are currently unable to predict the impact that recently imposed and possible future tariffs may have on our business. Trade tariffs have not had a material impact on our operations of financial performance to date. We are closely monitoring the impacts of trade tariffs and the potential effect they may have on our financial positions, results of operations, or cash flows.

Business Segment Recent Developments

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See Note 2 of the Notes to Consolidated Financial Statements in this Annual Report on Form 10-K for recent rate review activity for Colorado Electric.

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In December 2025, the Ready Wyoming project was fully completed and placed in service and now interconnects South Dakota Electric’s and Wyoming Electric’s transmission systems. Ready Wyoming was originally announced in November 2021 and construction commenced in late 2023. The project provides customers long-term price stability and greater flexibility as power markets develop in the western United States. This project is also expected to enable economic growth in Wyoming, expand access to renewable resources and facilitate additional renewable development across wind- and sun-rich resource areas.

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In 2025, Wyoming Electric continued to grow its large-load demand from existing data center customers, Microsoft and Meta, under its LPCS Tariff. In July 2024, Wyoming Electric announced it would partner with Meta to provide power for its AI data center. Meta's new AI data center plans to transition from construction power to permanent service later in the first quarter of 2026. We are also actively negotiating with prospective new data center customers that would further grow our load pipeline under Wyoming Electric's LPCS Tariff and also through strategic investments in new transmission and generation.

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In 2025, Wyoming Electric set multiple all-time and winter records for System Peak Demand. The most recent all-time peak of 379 MW was set on June 20, 2025 and the most recent winter peak of 375 MW was set on November 30, 2025. Prior to 2025, the previous all-time and winter peak was 314 MW set on January 11, 2024.

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On March 28, 2025, South Dakota Electric filed a CPCN with the WPSC for the Lange II project, which was approved in June 2025. The new facility began construction in the third quarter of 2025 and is anticipated to be in service in the fourth quarter of 2026. The addition of these resources will replace generation facilities planned for retirement and support updated planning reserve margin requirements.

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In 2025, Colorado Electric received CPUC approval for the addition of 250 MW of new renewable generation resources in support of its Clean Energy Plan, which included a 50-MW utility-owned battery storage project and a 200-MW solar PPA. On November 3, the CPUC approved the CPCN for the 50-MW battery storage project. During the first quarter of 2026, Colorado Electric expects to execute the 200-MW solar PPA.

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In 2024, we published our first formal WMP, which is an overview of our three-layered approach to manage wildfire risks driven by asset-based risk assessments that include asset programs, integrity programs and operational response. On June 30, 2025, we established our Emergency PSPS program across all three of our electric utilities to promote customer safety and mitigate wildfire risk. In establishing the Emergency PSPS program, we engaged with wildfire experts and key stakeholders including customers, community and local agencies, regulators and community leaders.

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On March 6, 2025, the state of Wyoming enacted comprehensive wildfire liability mitigation legislation (HB0192), effective July 1, 2025. The legislation provides material liability protections for a utility that complies with its commission-approved wildfire mitigation plan. In November 2025, we filed our WMP with the WPSC and anticipate approval in March 2026.

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See Note 2 of the Notes to Consolidated Financial Statements in this Annual Report on Form 10-K for recent rate review activity for Arkansas Gas, Iowa Gas, Kansas Gas, and Nebraska Gas.

Corporate and Other

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See Note 8 of the Notes to Consolidated Financial Statements in this Annual Report on Form 10-K for information regarding our corporate Revolving Credit Facility, October 2, 2025 debt offering and ATM program activity.