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 14 of the Condensed Notes to Consolidated Financial Statements for recent developments surrounding the pending Merger.

Business Segment Recent Developments

Electric Utilities

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See Note 2 of the Condensed Notes to Consolidated Financial Statements for recent rate review activity for South Dakota Electric and Colorado Electric.

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During the second quarter of 2026, South Dakota Electric continued with construction of its Lange II project which 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. On August 4, 2026, South Dakota Electric filed an application with the SDPUC for a PIRP rider which requests recovery of $320 million of Lange II project costs outside of a general rate review. If approved by the SDPUC, the rider is anticipated to be effective on December 1, 2026.

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On March 12, 2026, the state of South Dakota enacted comprehensive wildfire liability mitigation legislation (Senate Bill 36), effective July 1, 2026. The legislation provides material liability protections for a utility that complies with its published wildfire mitigation plan. On July 2, 2026, South Dakota Electric filed its WMP with the SDPUC. Under Senate Bill 36, a utility's WMP is valid and current if it is on file and all annual reports are timely filed with the SDPUC. In 2025, the state of Wyoming enacted similar legislation. In November 2025, Wyoming Electric filed its WMP with the WPSC, which was approved on July 9, 2026.

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On April 22, 2026, Wyoming Electric entered into a generation reservation agreement with a prospective new customer seeking to construct a 1.8 GW data center under Wyoming Electric's LPCS Tariff. In July 2026, the parties amended this generation reservation agreement to increase the total refundable advances and extended the maturity date to August 31, 2026. This agreement is a bridge agreement to support long lead-time items while Wyoming Electric continues to negotiate definitive agreements with the prospective customer. See Note 5 of the Condensed Notes to Consolidated Financial Statements for additional information.

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On June 30, 2026, Wyoming Electric submitted an IRP to the WPSC. The IRP, which is based on 20-year planning period including a near-term planning period through 2033, identified a near-term capacity shortfall of 95 MW beginning in 2027. Based on its forecasts and analysis, Wyoming Electric recommends the addition of natural gas-fired generation and battery storage assets to meet the identified resource need. Wyoming Electric's IRP does not address any LPCS Tariff capacity needs, which are handled separately under customer-specific agreements.

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On June 19, 2026, Wyoming Electric filed a request with the WPSC to establish an LCTCAM tariff. The LCTCAM tariff provides a framework to directly recover transmission investment costs from LPCS customers who are served by, and benefit from, the transmission facility. The proposed mechanism is designed to ensure that customers not directly served by those facilities are protected from bearing those costs. The filing requests WPSC approval of the LCTCAM tariff by September 1, 2026, with an effective date of January 1, 2027.

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In 2026, Wyoming Electric has set multiple all-time records for System Peak Demand. The most recent all-time peak of 439 MW was set on July 20, 2026. Prior to 2026, the previous all-time peak was 379 MW set on June 20, 2025.

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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. During the fourth quarter of 2025, Colorado Electric commenced construction of the 50-MW battery storage project. The project is expected to be completed by year-end 2027. On February 18, 2026, Colorado Electric entered into a 200-MW solar PPA. See Note 3 of the Condensed Notes to Consolidated Financial Statements for additional information regarding the PPA.

Gas Utilities

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See Note 2 of the Condensed Notes to Consolidated Financial Statements for recent rate review activity for Arkansas Gas, Kansas Gas and Nebraska Gas.

Corporate and Other

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See Note 5 of the Condensed Notes to Consolidated Financial Statements for information regarding recent financing activities.

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During the second quarter of 2026, we published our 2025 Corporate Sustainability Report, highlighting our environmental, social and governance impacts and our progress on major projects and climate goals. We reported a 43% reduction in electric utility emissions intensity compared to 2005, driven by the addition of renewable and natural gas resources and the retirement of aging power plants. We also reduced natural gas utility emissions by 25% since 2022, including a 53% reduction from transfer stations, reflecting progress toward our net-zero by 2035 goal through expanded leak detection and repair efforts.