Black Hills (NYSE: BKH) outlines pro forma impact of NorthWestern all-stock merger

Rhea-AI Filing Summary

Black Hills Corporation filed an update to give investors detailed financial information about its pending all-stock merger with NorthWestern Energy Group. The filing adds NorthWestern’s latest quarterly financial statements and unaudited pro forma results showing how the two utilities would look as a combined company.

The Merger Agreement calls for each NorthWestern share to be exchanged for 0.98 Black Hills shares, with Black Hills treated as the accounting acquirer. Based on a recent Black Hills share price, the estimated merger consideration is about $4.55 billion, with a large portion recorded as goodwill under purchase accounting.

The pro forma combined income statements illustrate how revenue, earnings and earnings per share would have appeared if the merger had been completed earlier, but the company emphasizes these figures are preliminary, rely on assumptions and do not predict future performance. Completion of the merger still depends on multiple regulatory approvals and satisfaction of other closing conditions.

Insights

Utility mergers analyst

Filing adds detail on a large utility merger but no new decision point.

The disclosure expands financial transparency around the planned all-stock combination of Black Hills and NorthWestern. It includes full NorthWestern quarterly results and detailed pro forma statements prepared under acquisition accounting, with Black Hills as the accounting acquirer.

Estimated merger consideration of about $4.55 billion is tied to an exchange ratio of 0.98 Black Hills shares for each NorthWestern share and a recent Black Hills share price. A substantial portion is allocated to goodwill, reflecting expected synergies and the premium over net assets.

Regulatory approvals from FERC and several state commissions, along with other closing conditions, remain outstanding, so timing and ultimate terms could still evolve. Future company and regulatory filings will determine whether the transaction closes on the anticipated second-half 2026 timeline and how final purchase accounting is resolved.

8-K Event Classification

2 items: 8.01, 9.01

2 items

Item 8.01 Other Events Other

Voluntary disclosure of events the company deems important to shareholders but not covered by other items.

Item 9.01 Financial Statements and Exhibits Exhibits

Financial statements, pro forma financial information, and exhibit attachments filed with this report.

Key Figures

Exchange ratio: 0.98 Black Hills shares per NorthWestern share Estimated merger consideration: $4.551 billion NorthWestern Q1 2026 revenue: $497.570 million +5 more

8 metrics

Exchange ratio 0.98 Black Hills shares per NorthWestern share Merger consideration terms

Estimated merger consideration <money>$4.551&nbsp;billion</money> Preliminary fair value of total consideration

NorthWestern Q1 2026 revenue <money>$497.570&nbsp;million</money> Three months ended March 31, 2026

NorthWestern Q1 2026 net income <money>$63.456&nbsp;million</money> Three months ended March 31, 2026

Pro forma combined Q1 2026 revenue <money>$1.278&nbsp;billion</money> Black Hills + NorthWestern illustrative combined

Pro forma Q1 2026 net income to common <money>$195&nbsp;million</money> Combined company, illustrative

Pro forma basic EPS Q1 2026 <money>$1.43</money> per share Combined company, illustrative EPS

Preliminary goodwill <money>$1.918&nbsp;billion</money> Excess of consideration over net assets

Key Terms

all-stock merger, pro forma condensed combined financial statements, Exchange Ratio, goodwill, +2 more

6 terms

all-stock merger financial

"provides for an all-stock business combination of Black Hills and NorthWestern upon the terms and subject to the conditions"

An all-stock merger is a deal in which one company combines with another by paying only with shares rather than cash, so owners of the target company receive new stock in the combined business. For investors this matters because it changes who owns what percentage of the merged company, can dilute existing shareholders, ties the value of the deal to future share performance, and signals that management prefers using equity over cash for the transaction—like paying with IOUs that depend on how well the new company does.

pro forma condensed combined financial statements financial

"pro forma financial information of Black Hills and NorthWestern on a combined basis in accordance with Article 11 of Regulation S-X"

Exchange Ratio financial

"each share of NorthWestern... will be converted into the right to receive 0.98... shares of Black Hills Common Stock (the "Exchange Ratio")"

The exchange ratio is the number used to decide how many shares of one company you get for each share you own in another company during a merger or acquisition. It’s like a recipe that tells you how to swap shares fairly, ensuring both companies’ values are balanced. This ratio matters because it determines how ownership divides between the companies' shareholders.

goodwill financial

"Any differences between the fair value of the consideration transferred and the fair value of the assets acquired and liabilities assumed will be recorded as goodwill."

Goodwill is the extra value a buyer pays for a company above the measurable worth of its buildings, inventory and other tangible items, reflecting things like brand reputation, customer loyalty and expected future profits. Think of paying more for a café because of its famous name and regulars rather than its furniture alone. It matters to investors because changes in goodwill — for example a write-down if expected benefits don’t materialize — can reduce reported earnings and signal that past acquisitions aren’t delivering as hoped.

Hart-Scott-Rodino Antitrust Improvements Act regulatory

"the waiting period under the Hart-Scott-Rodino Antitrust Improvements Act expired, permitting consummation of the transaction"

A U.S. law that requires companies planning large mergers or acquisitions to notify federal antitrust authorities and wait for review before completing the deal. Think of it like applying for a building permit: regulators check whether the combined business would unfairly hurt competition and can clear the deal, impose changes, or seek to stop it, so the process affects transaction timing, cost, and whether expected benefits reach investors.

Power Cost and Credit Adjustment Mechanism (PCCAM) financial

"suspended the 90/10 cost sharing mechanism of the Power Cost and Credit Adjustment Mechanism (PCCAM) on a temporary basis"

A power cost and credit adjustment mechanism (PCCAM) is a regulatory tool that lets utilities automatically raise or lower customer charges to reflect changes in the cost of generating or buying electricity and any related credits. For investors, it matters because PCCAMs shift short-term fuel and purchase-price risk away from the utility’s profits and onto customers, smoothing revenue and cash flow but exposing returns to regulatory and demand changes—like a thermostat that keeps a company’s income steady despite swings in energy costs.

Understanding 8-K Material Events →

0001130464false00011304642026-05-152026-05-15

UNITED STATES
SECURITIES AND EXCHANGE COMMISSION
WASHINGTON, D.C. 20549

FORM 8-K

CURRENT REPORT

Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934

Date of Report (Date of earliest event reported): May 15, 2026

Black Hills Corporation

(Exact name of Registrant as Specified in Its Charter)

South Dakota			001-31303	46-0458824
(State or Other Jurisdiction of Incorporation)			(Commission File Number)	(IRS Employer Identification No.)
7001 Mount Rushmore Road
Rapid City, South Dakota				57702
(Address of Principal Executive Offices)				(Zip Code)

Registrant’s Telephone Number, Including Area Code: 605 721-1700

(Former Name or Former Address, if Changed Since Last Report)

Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the registrant under any of the following provisions:

☐Written communications pursuant to Rule 425 under the Securities Act (17 CFR 230.425)

☐Soliciting material pursuant to Rule 14a-12 under the Exchange Act (17 CFR 240.14a-12)

☐Pre-commencement communications pursuant to Rule 14d-2(b) under the Exchange Act (17 CFR 240.14d-2(b))

☐Pre-commencement communications pursuant to Rule 13e-4(c) under the Exchange Act (17 CFR 240.13e-4(c))

Securities registered pursuant to Section 12(b) of the Act:

Title of each class		Trading Symbol(s)		Name of each exchange on which registered
Common stock of $1.00 par value		BKH		The New York Stock Exchange

Indicate by check mark whether the registrant is an emerging growth company as defined in Rule 405 of the Securities Act of 1933 (§ 230.405 of this chapter) or Rule 12b-2 of the Securities Exchange Act of 1934 (§ 240.12b-2 of this chapter).

Emerging growth company ☐

If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 13(a) of the Exchange Act. ☐

Item 8.01 Other Events.

Black Hills Corporation ("Black Hills" or the "Company") is filing this Current Report on Form 8-K solely to provide certain information relating to the pending merger transaction involving Black Hills and NorthWestern Energy Group, Inc., a Delaware corporation (“NorthWestern”). As previously disclosed in its Current Report on Form 8-K filed on August 19, 2025, Black Hills entered into an Agreement and Plan of Merger (the “Merger Agreement”) on August 18, 2025 with NorthWestern and River Merger Sub Inc., a Delaware corporation and direct wholly owned subsidiary of Black Hills. The Merger Agreement, which was unanimously approved on August 18, 2025 by both the board of directors of Black Hills and the board of directors of NorthWestern, provides for an all-stock business combination of Black Hills and NorthWestern upon the terms and subject to the conditions set forth therein. Such conditions include, among other things, regulatory approvals, including approval from certain state regulatory commissions, as well as the Federal Energy Regulatory Commission.

This Item 8.01 contains:

1.Historical financial statements of NorthWestern filed in accordance with Rule 3-05 of Regulation S-X, included as Exhibit 99.1, which are incorporated herein by reference; and

2.Pro forma financial information of Black Hills and NorthWestern on a combined basis in accordance with Article 11 of Regulation S-X giving effect to certain pro forma adjustments related to the pending merger transaction as if it were completed on January 1, 2025 as it relates to the pro forma combined condensed statement of income, and as if it were completed on March 31, 2026 as it relates to the pro forma combined condensed balance sheet, included as Exhibit 99.2 hereto, which is incorporated herein by reference.

The pro forma information and related notes have been prepared for illustrative purposes only, based upon applicable rules of the Securities and Exchange Commission. The pro forma information does not purport to be indicative of what the combined company’s consolidated financial position or results of operations actually would have been had the pending merger transaction been completed as of the dates indicated. In addition, the unaudited pro forma combined condensed financial information does not purport to project the future financial position or operating results of the combined company. The pro forma adjustments, which are subject to uncertainties, are based on the information available at the time of the preparation of these pro forma financial statements and on the basis of certain assumptions and estimates. The pro forma financial information should be read, if at all, with the related qualifications and other notes set forth in Exhibit 99.2.

This Report does not modify or update the consolidated financial statements of Black Hills included in the Company’s periodic reports. The historical financial statements of NorthWestern included as Exhibit 99.1 were prepared by NorthWestern and previously disclosed by NorthWestern in its periodic reports; it has not been independently validated or reviewed by Black Hills.

* * *

Forward-Looking Statements

This Current Report on Form 8-K contains statements reflecting assumptions, expectations, projections, intentions or beliefs about future events that are intended as “forward-looking statements.” We make these forward-looking statements in reliance on the safe harbor protections provided under the Private Securities Litigation Reform Act of 1995. All statements, other than statements of historical facts, included in this Current Report on Form 8-K that address activities, events or developments that we expect, believe or anticipate will or may occur in the future are forward-looking statements. This includes, without limitations, completion of the merger transaction with NorthWestern and statements about the benefits of the proposed transaction between Black Hills and NorthWestern including future financial and operating results. These forward-looking statements are based on assumptions which we believe are reasonable based on current expectations and projections about future events and industry conditions and trends affecting our business. However, whether actual results and developments will conform to our expectations and predictions is subject to a number of risks and uncertainties that, among other things, could cause actual results to differ materially from those contained in the forward-looking statements.

All forward-looking statements are subject to risks, uncertainties and other factors that may cause the actual results, performance or achievements of Black Hills or NorthWestern to differ materially from any results expressed or implied by such forward-looking statements. Such factors include, among others, (1) the risk of delays in consummating the pending merger transaction, including as a result of required governmental and regulatory approvals, which may not be obtained on the expected timeline, or at all, (2) the risk of any event, change or other circumstance that could give rise to the termination of the Merger Agreement, (3) the risk that required regulatory approvals are subject to conditions not anticipated by Black Hills and NorthWestern, (4) the possibility that any of the anticipated benefits and projected synergies of the pending merger transaction will not be realized or will not be realized within the expected time period, (5) disruption to the parties’ businesses as a result of the announcement and pendency of the merger transaction, including potential distraction of management from current plans and operations of Black Hills or NorthWestern and the ability of Black Hills or NorthWestern to retain and hire key personnel, (6) reputational risk and the reaction of each company’s customers, suppliers, employees or other business partners to the pending merger transaction, (7) the possibility that the pending merger transaction may be more expensive to complete than anticipated, including as a result of unexpected factors or events, (8) the outcome of any legal or regulatory proceedings that may be instituted against Black Hills or NorthWestern related to the Merger Agreement or the pending merger transaction, (9) the risks associated with third party contracts containing consent and/or other provisions that may be triggered by the pending merger transaction, (10) legislative, regulatory, political, market, economic and other conditions, developments and uncertainties affecting Black Hills’ or NorthWestern’s businesses; (11) the evolving legal, regulatory and tax regimes under which Black Hills and NorthWestern operate; (12) restrictions during the pendency of the merger transaction that may impact Black Hills’ or NorthWestern's ability to pursue certain business opportunities or strategic transactions; and (13) unpredictability and severity of catastrophic events, including, but not limited to, extreme weather, natural disasters, acts of terrorism or outbreak of war or hostilities, as well as Black Hills’ and NorthWestern’s response to any of the aforementioned factors.

Additional factors which could affect future results of Black Hills and NorthWestern can be found in both Black Hills’ and NorthWestern’s Annual Reports on Form 10-K, Quarterly Reports on Form 10-Q, and Current Reports on Form 8-K, in each case filed with the SEC and available on the SEC’s website at http://www.sec.gov. Black Hills and NorthWestern disclaim any obligation and do not intend to update or revise any forward-looking statements contained in this communication, which speak only as of the date hereof, whether as a result of new information, future events or otherwise, except as required by federal securities laws.

Item 9.01 Financial Statements and Exhibits.

Exhibit No.	Description
99.1	Unaudited consolidated financial statements of NorthWestern Energy Group, Inc. as of and for the three months ended March 31, 2026 and 2025
99.2	Unaudited pro forma condensed combined financial statements (a) as of and for the three months ended March 31, 2026 and (b) for the year ended December 31, 2025
104	Cover Page Interactive Data File (formatted as the inline XBRL document)

SIGNATURES

Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned hereunto duly authorized.

			BLACK HILLS CORPORATION
Date:	May 15, 2026	By:	/s/ Kimberly F. Nooney
			Kimberly F. Nooney Senior Vice President and Chief Financial Officer

NORTHWESTERN ENERGY GROUP

CONDENSED CONSOLIDATED STATEMENTS OF INCOME

(Unaudited)

(in thousands, except per share amounts)

	Three Months Ended March 31,
	2026				2025
Revenues
Electric	$	362,054		$	335,483
Gas		135,516			131,147
Total Revenues		497,570			466,630
Operating expenses
Fuel, purchased supply and direct transmission expense (exclusive of depreciation and depletion shown separately below)		145,565			138,197
Operating and maintenance		74,540			56,709
Administrative and general		46,119			41,357
Property and other taxes		50,404			43,240
Depreciation and depletion		66,831			62,400
Total Operating Expenses		383,459			341,903
Operating income		114,111			124,727
Interest expense, net		(39,916)			(36,511)
Other income, net		3,057			3,928
Income before income taxes		77,252			92,144
Income tax expense		(13,796)			(15,204)
Net Income	$	63,456		$	76,940
Average Common Shares Outstanding		61,461			61,339
Basic Earnings per Average Common Share	$	1.03		$	1.25
Diluted Earnings per Average Common Share	$	1.03		$	1.25
Dividends Declared per Common Share	$	0.67		$	0.66

See Notes to Condensed Consolidated Financial Statements

NORTHWESTERN ENERGY GROUP
CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME
	(Unaudited)
	(in thousands)
		Three Months Ended March 31,
		2026				2025
Net Income		$	63,456		$	76,940
Other comprehensive income, net of tax:
Foreign currency translation adjustment			(1)			1
Reclassification of net losses on derivative instruments			113			113
Total Other Comprehensive Income			112			114
Comprehensive Income		$	63,568		$	77,054

See Notes to Condensed Consolidated Financial Statements

NORTHWESTERN ENERGY GROUP
CONDENSED CONSOLIDATED BALANCE SHEETS
(Unaudited)
(in thousands, except share data)
ASSETS		March 31, 2026			December 31, 2025
	Current Assets:
Cash and cash equivalents	$	5,861		$	8,781
Restricted cash		21,744			21,957
Accounts receivable, net		199,275			209,751
Inventories		134,071			132,506
Regulatory assets		103,237			92,937
Prepaid expenses and other		48,984			38,010
Total current assets		513,172			503,942
Property, plant, and equipment, net		6,794,000			6,738,849
Goodwill		367,635			367,635
Regulatory assets		773,589			772,634
Other noncurrent assets		134,110			76,631
Total Assets	$	8,582,506		$	8,459,691
LIABILITIES AND SHAREHOLDERS' EQUITY
	Current Liabilities:
Current maturities of finance leases	$	1,844		$	1,865
Current portion of long-term debt		104,983			104,967
Short-term borrowings		150,000			150,000
Accounts payable		121,796			129,633
Accrued expenses and other		321,104			272,373
Regulatory liabilities		31,195			38,613
Total current liabilities		730,922			697,451
Long-term finance leases		8,436			—
Long-term debt		3,177,528			3,181,040
Deferred income taxes		750,719			733,064
Noncurrent regulatory liabilities		684,664			678,861
Other noncurrent liabilities		321,353			283,535
Total Liabilities		5,673,622			5,573,951
Commitments and Contingencies (Note 11)
Shareholders' Equity:
Common stock, par value $0.01; authorized 200,000,000 shares; issued and outstanding 65,001,449 and 61,503,442 shares, respectively; Preferred stock, par value $0.01; authorized 50,000,000 shares; none issued		650			649
Treasury stock at cost		(99,186)			(97,503)
Paid-in capital		2,094,232			2,091,935
Retained earnings		919,137			896,720
Accumulated other comprehensive loss		(5,949)			(6,061)
Total Shareholders' Equity		2,908,884			2,885,740
Total Liabilities and Shareholders' Equity	$	8,582,506		$	8,459,691

See Notes to Condensed Consolidated Financial Statements

NORTHWESTERN ENERGY GROUP

CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS

(Unaudited)

(in thousands)

Three Months Ended March 31,

OPERATING ACTIVITIES:		2026			2025
	Net income	$	63,456		$	76,940
Adjustments to reconcile net income to cash provided by operations:
Depreciation and depletion		66,831			62,400
Amortization of debt issuance costs, premium, and deferred hedge gain		975			990
Stock-based compensation costs		2,045			2,284
Equity portion of allowance for funds used during construction		(1,941)			(1,797)
Loss on disposition of assets		9			149
Deferred income taxes		14,140			13,071
Changes in current assets and liabilities:
Accounts receivable		10,476			275
Inventories		(1,565)			3,335
Other current assets		(10,974)			5,510
Accounts payable		(7,984)			(14,992)
Accrued expenses and other		48,746			24,792
Regulatory assets		(10,300)			(12,711)
Regulatory liabilities		(7,418)			(6,335)
Other noncurrent assets and liabilities		(7,082)			(519)
Cash Provided by Operating Activities		159,414			153,392
INVESTING ACTIVITIES:
Property, plant, and equipment additions		(116,080)			(92,124)
Investment in debt & equity securities		—			(4,584)
Cash Used in Investing Activities		(116,080)			(96,708)
FINANCING ACTIVITIES:
Dividends on common stock		(41,038)			(40,307)
Issuance of long-term debt		—			400,000
Line of credit repayments, net		(4,000)			(362,000)
Other financing activities, net		(1,429)			(3,328)
Cash Used in Financing Activities		(46,467)			(5,635)
(Decrease) Increase in Cash, Cash Equivalents, and Restricted Cash		(3,133)			51,049
Cash, Cash Equivalents, and Restricted Cash, beginning of period		30,738			29,017
Cash, Cash Equivalents, and Restricted Cash, end of period	$	27,605		$	80,066
Supplemental Cash Flow Information:
	Cash (received) paid during the period for:
Production tax credits(1)		—			(8,255)
Interest		44,166			32,768
Significant non-cash transactions:
Capital expenditures included in accounts payable		41,848			14,028

(1) Proceeds from production tax credits transferred are included in cash provided by operating activities within the Condensed Consolidated Statement of Cash Flows.

See Notes to Condensed Consolidated Financial Statements

NORTHWESTERN ENERGY GROUP

CONDENSED CONSOLIDATED STATEMENTS OF SHAREHOLDERS’ EQUITY

(Unaudited)

(in thousands, except per share data)

									Three Months Ended March 31,
	Number of		Number of			Common			Treasury						Retained		Accumulated Other				Total
	Common		Treasury											Paid in Capital							Comprehensive			Shareholders'
	Shares		Shares			Stock			Stock									Earnings			Loss			Equity
Balance at December 31, 2024	64,811		3,490		$	648		$	(97,394)		$	2,084,133		$	877,017		$	(6,704)		$	2,857,700
Net income	—		—			—			—			—			76,940			—			76,940
Foreign currency translation	—		—			—			—			—			—			1			1
adjustment, net of tax
Reclassification of net losses on
derivative instruments from OCI to net	—		—			—			—			—			—			113			113
income, net of tax
Stock-based compensation	59		—			1			(729)			2,272			—			—			1,544
Issuance of shares	—		7			—			188			189			—			—			377
Dividends on common stock ($0.660	—		—			—			—			—			(40,307)			—			(40,307)
per share)
Balance at March 31, 2025	64,870		3,497		$	649		$	(97,935)		$	2,086,594		$	913,650		$	(6,590)		$	2,896,368
Balance at December 31, 2025	64,895		3,477		$	649		$	(97,503)		$	2,091,935		$	896,720		$	(6,061)		$	2,885,740
Net income	—		—			—			—			—			63,456			—			63,456
Foreign currency translation	—		—			—			—			—			—			(1)			(1)
adjustment, net of tax
Reclassification of net losses on
derivative instruments from OCI to net	—		—			—			—			—			—			113			113
income, net of tax
Stock-based compensation	106		28			1			(1,874)			2,036			—			—			163
Issuance of shares	—		(7)			—			191			261			—			—			452
Dividends on common stock ($0.670	—		—			—			—			—			(41,039)			—			(41,039)
per share)
Balance at March 31, 2026	65,001		3,498			650			(99,186)			2,094,232			919,137			(5,949)			2,908,884

See Notes to Condensed Consolidated Financial Statements

NOTES TO CONDENSED CONSOLIDATED FINANCIAL STATEMENTS

(Reference is made to Notes to Financial Statements included in the NorthWestern Energy Group's Annual Report)

(Unaudited)

(1) Nature of Operations and Basis of Consolidation

NorthWestern Energy Group, doing business as NorthWestern Energy, provides electricity and/or natural gas to approximately 850,300 customers in Montana, South Dakota, Nebraska and Yellowstone National Park, through its subsidiaries NorthWestern Corporation (NW Corp) and NorthWestern Energy Public Service Corporation (NWE Public Service). We have generated and distributed electricity in South Dakota and distributed natural gas in South Dakota and Nebraska since 1923 and have generated and distributed electricity and distributed natural gas in Montana since 2002.

The preparation of financial statements in conformity with accounting principles generally accepted in the United States of America (GAAP) requires us to make estimates and assumptions that may affect the reported amounts of assets, liabilities, revenues and expenses during the reporting period. Actual results could differ from those estimates. The unaudited Condensed Consolidated Financial Statements (Financial Statements) reflect all adjustments (which unless otherwise noted are normal and recurring in nature) that are, in our opinion, necessary to fairly present our financial position, results of operations and cash flows. The actual results for the interim periods are not necessarily indicative of the operating results to be expected for a full year or for other interim periods. Events occurring subsequent to March 31, 2026 have been evaluated as to their potential impact to the Financial Statements through the date of issuance.

The Financial Statements included herein have been prepared by NorthWestern, without audit, pursuant to the rules and regulations of the SEC. Certain information and footnote disclosures normally included in financial statements prepared in accordance with GAAP have been condensed or omitted pursuant to such rules and regulations; however, we believe that the condensed disclosures provided are adequate to make the information presented not misleading. We recommend that these Financial Statements be read in conjunction with the audited financial statements and related footnotes included in the NorthWestern Energy Group Annual Report on Form 10-K for the year ended December 31, 2025.

Supplemental Cash Flow Information

The following table provides a reconciliation of cash, cash equivalents, and restricted cash reported within the Condensed Consolidated Balance Sheets that sum to the total of the same such amounts shown in the Condensed Consolidated Statements of Cash Flows (in thousands):

	March 31,		December 31,		March 31,		December 31,
	2026		2025		2025		2024
Cash and cash equivalents	$	5,861	$	8,781	$	56,025	$	4,283
Restricted cash		21,744		21,957		24,041		24,734
Total cash, cash equivalents, and restricted cash shown in	$	27,605	$	30,738	$	80,066	$	29,017
the Condensed Consolidated Statements of Cash Flows

(2) Pending Merger with Black Hills Corporation

On August 18, 2025, we entered into a Merger Agreement with Black Hills and River Merger Sub, Inc., a Delaware corporation and direct wholly owned subsidiary of Black Hills (Merger Sub). The Merger Agreement provides for an all-stock merger of equals between NorthWestern and Black Hills upon the terms and subject to the conditions set forth therein. The Merger Agreement provides for Merger Sub to merge with and into NorthWestern, with NorthWestern continuing as the surviving entity and a direct wholly owned subsidiary of Black Hills, which would assume the new corporate name of Bright Horizon Energy as the resulting parent company of the combined corporate group. Under the provisions of ASC Topic 805, which requires the identification of an acquirer in a business combination, Black Hills is the accounting acquirer. Pursuant to the Merger Agreement, at the effective time of the Merger, each share of NorthWestern, par value $0.01 per share, issued and outstanding as of immediately prior to closing will be converted into the right to receive 0.98 validly issued, fully paid and non-assessable shares of Black Hills Common Stock.

In connection with this pending merger, we have incurred merger-related costs. During the three months ended March 31, 2026, we have incurred $3.4 million of merger-related costs, which are included in our Administrative and general expenses.

Regulatory and Shareholder Approvals

Our pending merger with Black Hills was unanimously approved by our board of directors and Black Hills' board of directors. In February 2026, the Form S-4, which contains joint proxy statement/prospectus for NorthWestern and Black Hills, was declared effective by the SEC. In April 2026, shareholders of each company voted to approve the Merger and the waiting period under the Hart-Scott-Rodino Antitrust Improvements Act expired, permitting consummation of the transaction. The completion of the Merger remains subject to the satisfaction or waiver of certain conditions to

closing, including (1) subject to certain conditions, the receipt of certain regulatory approvals, including approval from the Federal Energy Regulatory Commission (FERC), the Montana Public Service Commission (MPSC), the Nebraska Public Service Commission (NPSC), and the South Dakota Public Utilities Commission (SDPUC), in each case on such terms and conditions that would not result in a material adverse effect on Bright Horizon Energy; (2) the absence of any court order or regulatory injunction prohibiting the completion of the Merger; (3) the authorization for listing of shares of Black Hills Common Stock to be issued in the Merger on a mutually agreed stock exchange; (4) subject to specified materiality standards, the accuracy of the representations and warranties of each party; (5) compliance by each party in all material respects with its covenants; (6) the absence of a material adverse effect on each party; and (7) receipt of each party of an opinion relating to the anticipated tax-free treatment of the Merger.

We have filed applications with the MPSC, NPSC, SDPUC, and FERC for approval of the Merger. In March 2026, we reached a settlement agreement with the Public Advocate of Nebraska, which is subject to approval by the NPSC. A hearing with the NPSC was held in April 2026. In April 2026, we reached settlement agreements with certain key intervenors in both Montana and South Dakota, which are subject to approval by the MPSC and SDPUC, respectively. Hearings with the MPSC and SDPUC are scheduled in the second quarter of 2026. We anticipate the transaction closing in the second half of 2026, subject to the satisfaction or waiver of certain closing conditions.

(3) Regulatory Matters

Montana Rate Review

In December 2025, the MPSC issued a final order approving our partial electric settlement agreement. The final order also suspended the 90/10 cost sharing mechanism of the Power Cost and Credit Adjustment Mechanism (PCCAM) on a temporary basis pending further review by the MPSC. Within this final order, the MPSC disallowed a portion of the capital costs related to the construction of Yellowstone County Generating Station (YCGS). As a result, in the fourth quarter of 2025 we recorded a $30.9 million non-cash charge for the regulatory disallowance. As of March 31, 2026, we have $6.3 million reserved within Regulatory liabilities on the Condensed Consolidated Balance Sheets for interim rates to be refunded to customers.

In January 2026, we filed a Motion for Reconsideration (Motion) as it relates to this final order. Among other things, our Motion requests that the MPSC reconsider their prudence conclusions regarding the capital costs associated with the construction of YCGS and clarification as to the effective date of the PCCAM sharing mechanism suspension, for which we have requested an effective date of July 1, 2025, to align with the PCCAM tracker year. Any subsequent modifications by the MPSC to their final order will be reflected in our 2026 results.

Colstrip Acquisitions and Requests for Cost Recovery

In January 2023, and July 2024, we entered into definitive agreements with Avista Corporation (Avista) and Puget Sound Energy (Puget), respectively, to acquire their respective interests in Colstrip Units 3 and 4 for $0 and completed these acquisitions on January 1, 2026. Accordingly, we are responsible for the associated operating costs beginning on January 1, 2026, which we will not collect through utility base rates, until requested in a future Montana rate review. Puget and Avista will remain responsible for their respective pre-closing share of environmental, asset retirement obligations (AROs), and pension liabilities attributed to events or conditions existing prior to the closing of the transaction and for any future decommissioning and demolition costs associated with the existing facilities that comprise their interests.

While Puget and Avista remain contractually obligated for the pre-closing share of AROs, we remain the primary obligor. As such, as of March 31, 2026, we have recorded $2.8 million and $34.6 million within Accrued expenses and other and Other noncurrent liabilities, respectively, on the Condensed Consolidated Balance Sheets for these AROs, and we have recorded an indemnification asset of $2.8 million and $34.6 million with Prepaid expenses and other and Other noncurrent assets, respectively, on the Condensed Consolidated Balance Sheets.

Avista Interests - The 222 megawatts of generation capacity from Colstrip Units 3 and 4 acquired from Avista (Avista Interests) on January 1, 2026, was identified as a key element in our strategy to achieve resource adequacy for customers, as outlined in our 2023 Montana Integrated Resource Plan. Noting the costs associated with operating this resource are not currently reflected in utility customer rates, in August 2025, we filed a temporary PCCAM tariff waiver request with the MPSC that could provide a near-term cost-recovery mechanism to offset a portion of the approximately $18 million in annual incremental operating and maintenance costs associated with the Avista Interests. This waiver requested that the MPSC allow us to keep 100 percent of the net revenue associated with certain designated power sales contracts up to the amount of the operating and maintenance expenses we incur associated with our Avista Interests. Furthermore, the waiver request indicated that any net revenues from the designated contracts exceeding the operating and maintenance expenses associated with our Avista Interests would continue to flow back to retail customers. In January 2026, the MPSC approved our PCCAM tariff waiver request on an interim basis with final approval or denial subject to the ongoing PCCAM docket process.

Puget Interests - The 370 megawatts of generation capacity from Colstrip Units 3 and 4 acquired from Puget (Puget Interests) on January 1, 2026, increases our ownership share of the facility to 55 percent and provides an increase in voting share in determining strategic direction and investment decisions at the facility. Unlike the Avista Interests, we do not currently need this capacity to serve existing customers in Montana. As such, the Puget Interests are held by our FERC regulated subsidiary to isolate the costs associated with this acquired interest from our Montana retail customers. While we expect our future opportunity to serve growing customer demand, including large-load customers, may be supported by this resource, in October 2025, we signed a contract to sell the dispatchable capacity and associated energy from the Puget Interests beginning January 1,

2026, through late 2027. Revenues from this agreement are expected to largely offset the estimated $30 million of annual incremental operating and maintenance costs associated with the Puget Interests. In addition, in October 2025, we submitted a request to the FERC for approval of cost-based rates for our subsidiary that will own the Puget Interests. In February 2026, the FERC approved both the cost based rates and the contract rates retroactive to January 1, 2026. In March 2026, two MPSC commissioners, in their individual capacity, filed a motion with the FERC requesting a rehearing that largely reiterated arguments previously rejected by the FERC. We anticipate that the FERC will rule on this motion in the second quarter of 2026. If the FERC denies the motion, its prior approval order will stand. If the FERC grants the motion, it could reopen all or some portion of the proceedings.

(4) Income Taxes

We compute income tax expense for each quarter based on the estimated annual effective tax rate for the year, adjusted for certain discrete items. Our effective tax rate typically differs from the federal statutory tax rate due to the regulatory impact of flowing through the federal and state tax benefit of repairs deductions, state tax benefit of accelerated tax depreciation deductions (including bonus depreciation when applicable) and production tax credits. The regulatory accounting treatment of these deductions requires immediate income recognition for temporary tax differences of this type, which is referred to as the flow-through method. When the flow-through method of accounting for temporary differences is reflected in regulated revenues, we record deferred income taxes and establish related regulatory assets and liabilities.

During the three months ended March 31, 2026 income tax expense was $13.8 million compared to $15.2 million for the same period in 2025. For the three months ended March 31, 2026, the effective tax rate was 17.9% compared to 16.5% for the same period in 2025. The higher effective tax rate was primarily due to lower production tax credits.

(5) Comprehensive Income (Loss)

The following tables display the components of Other Comprehensive Income (Loss), after-tax, and the related tax effects (in thousands):

								Three Months Ended
			March 31, 2026									March 31, 2025
		Before-Tax		Tax Expense				Net-of-Tax			Before-Tax		Tax Expense				Net-of-Tax
		Amount									Amount						Amount						Amount
Foreign currency translation adjustment	$	(1)		$	—		$	(1)		$	1		$	—		$	1
Reclassification of net income on derivative
instruments		153			(40)			113			153			(40)			113
Other comprehensive income (loss)	$	152		$	(40)		$	112		$	154		$	(40)		$	114

Balances by classification included within accumulated other comprehensive loss (AOCL) on the Condensed Consolidated Balance Sheets are as follows, net of tax (in thousands):

		March 31, 2026			December 31, 2025
Foreign currency translation	$	1,450		$	1,451
Derivative instruments designated as cash flow hedges		(8,356)			(8,469)
Postretirement medical plans		957			957
Accumulated other comprehensive loss	$	(5,949)		$	(6,061)

The following tables display the changes in AOCL by component, net of tax (in thousands):

							Three Months Ended
							March 31, 2026
	Affected Line Item			Interest Rate
	in the Condensed			Derivative
	Consolidated			Instruments			Postretirement		Foreign Currency
	Statements of			Designated as														Total
	Income		Cash Flow Hedges				Medical Plans		Translation
Beginning balance			$	(8,469)		$	957		$	1,451		$	(6,061)
Other comprehensive loss before
reclassifications				—			—			(1)			(1)
Amounts reclassified from AOCL	Interest Expense			113			—			—			113
Net current-period other comprehensive income
(loss)				113			—			(1)			112
Ending balance			$	(8,356)		$	957		$	1,450		$	(5,949)
							Three Months Ended
							March 31, 2025
	Affected Line Item			Interest Rate
	in the Condensed			Derivative
	Consolidated			Instruments			Postretirement		Foreign Currency
	Statements of			Designated as									Total
	Income		Cash Flow Hedges				Medical Plans		Translation
Beginning balance			$	(8,921)		$	784		$	1,433		$	(6,704)
Other comprehensive income before
reclassifications				—			—			1			1
Amounts reclassified from AOCL	Interest Expense			113			—			—			113
Net current-period other comprehensive income				113			—			1			114
Ending balance			$	(8,808)		$	784		$	1,434		$	(6,590)

(6) Financing Activities

On April 9, 2026, we amended our existing NorthWestern Energy Group $150.0 million Term Loan Credit Agreement (Term Loan) to extend the maturity date from April 10, 2026 to December 31, 2026.

We exercised a five-year renewal option on a default supply procurement agreement, which we have recorded as a finance lease on our Condensed Consolidated Balance Sheets. As a result, the finance lease term was extended and will mature on June 30, 2031.

On April 28, 2026, NWE Public Service priced $150.0 million aggregate principal amount of South Dakota First Mortgage Bonds at a fixed interest rate of 5.51 percent maturing on June 15, 2036. We expect to complete the issuance and sale of these bonds on June 15, 2026. A portion of the proceeds will be utilized to redeem all $60.0 million of NWE Public Service's 2.80 percent South Dakota First Mortgage Bonds due on June 15, 2026.

(7) Segment Information

Our reportable segments are engaged in the electric and natural gas utility businesses.

Our Chief Operating Decision Maker (CODM), who is our Chief Executive Officer, uses segment net income to evaluate if our operating segments are earning their authorized rate of return and in the annual budget and forecasting process. Our CODM also uses segment net income to determine how to allocate capital resources between our operating segments and when to allocate the resources necessary to file for rate reviews. Segment asset and capital expenditure information is not provided for our reportable segments. As an integrated electric and gas utility, we operate significant assets that are not dedicated to a specific reportable segment.

Financial data for the reportable segments are as follows (in thousands):
Three Months Ended
March 31, 2026		Electric			Gas			Total
Operating revenues	$	362,054		$	135,516		$	497,570
Fuel, purchased supply and direct transmission expense (exclusive of depreciation
and depletion shown separately below)		90,275			55,290			145,565
Operating, general, and administrative		89,601			27,131			116,732
Property and other taxes		39,211			11,152			50,363
Depreciation and depletion		55,469			11,362			66,831
Interest expense, net		(30,185)			(7,871)			(38,056)
Other income, net		1,545			624			2,169
Income tax expense		(11,483)			(3,135)			(14,618)
Segment net income	$	47,375		$	20,199		$	67,574
Reconciliation to consolidated net income
Other, net(1)								(4,118)
Consolidated net income							$	63,456

Three Months Ended
March 31, 2025		Electric			Gas			Total
Operating revenues	$	335,483		$	131,147		$	466,630
Fuel, purchased supply and direct transmission expense (exclusive of depreciation
and depletion shown separately below)		92,752			45,445			138,197
Operating, general, and administrative		72,479			25,170			97,649
Property and other taxes		33,286			9,795			43,081
Depreciation and depletion		52,488			9,912			62,400
Interest expense, net		(27,756)			(7,034)			(34,790)
Other income, net		2,490			1,091			3,581
Income tax expense		(9,872)			(4,427)			(14,299)
Segment net income	$	49,340		$	30,455		$	79,795
Reconciliation to consolidated net income
Other, net(1)								(2,855)
Consolidated net income							$	76,940

(1) Consists of unallocated corporate costs, including merger-related costs, and certain limited unregulated activity within the energy industry.

(8) Revenue from Contracts with Customers

Nature of Goods and Services

We provide retail electric and natural gas services to three primary customer classes. Our largest customer class consists of residential customers, which includes single private dwellings and individual apartments. Our commercial customers consist primarily of main street businesses, and our industrial customers consist primarily of manufacturing and processing businesses that turn raw materials into products.

Electric Segment - Our regulated electric utility business primarily provides generation, transmission, and distribution services to customers in our Montana and South Dakota jurisdictions. We recognize revenue when electricity is delivered to the customer. Payments on our tariff-based sales are generally due 20-30 days after the billing date.

Natural Gas Segment - Our regulated natural gas utility business primarily provides production, storage, transmission, and distribution services to customers in our Montana, South Dakota, and Nebraska jurisdictions. We recognize revenue when natural gas is delivered to the customer. Payments on our tariff-based sales are generally due 20-30 days after the billing date.

Disaggregation of Revenue

The following tables disaggregate our revenue by major source and customer class (in thousands):

								Three Months Ended
				March 31, 2026									March 31, 2025
		Electric			Natural Gas			Total			Electric			Natural Gas			Total
Montana	$	120,438		$	48,138		$	168,576		$	114,977		$	51,418		$	166,395
South Dakota		23,229			14,524			37,753			22,292			15,570			37,862
Nebraska		—			11,161			11,161			—			13,209			13,209
Residential		143,667			73,823			217,490			137,269			80,197			217,466
Montana		106,482			26,877			133,359			96,952			26,758			123,710
South Dakota		31,397			11,754			43,151			29,315			11,175			40,490
Nebraska		—			6,506			6,506			—			7,441			7,441
Commercial		137,879			45,137			183,016			126,267			45,374			171,641
Industrial		11,864			791			12,655			10,100			484			10,584
Lighting, governmental, irrigation, and interdepartmental		5,509			524			6,033			4,693			591			5,284
Total Retail Revenues		298,919			120,275			419,194			278,329			126,646			404,975
Regulatory Amortization		12,277			(1,001)			11,276			27,690			(9,436)			18,254
Transmission		28,765			—			28,765			26,555			—			26,555
Transportation, wholesale and other		22,093			16,242			38,335			2,909			13,937			16,846
Total Revenues	$	362,054		$	135,516		$	497,570		$	335,483		$	131,147		$	466,630

(9) Earnings Per Share

Basic earnings per share are computed by dividing earnings applicable to common stock by the weighted average number of common shares outstanding for the period. Diluted earnings per share reflect the potential dilution of common stock equivalent shares that could occur if unvested shares were to vest. Common stock equivalent shares are calculated using the treasury stock method, as applicable. The dilutive effect is computed by dividing earnings applicable to common stock by the weighted average number of common shares outstanding plus the effect of the outstanding unvested restricted stock and performance share awards. Average shares used in computing the basic and diluted earnings per share are as follows:

	Three Months Ended
	March 31, 2026	March 31, 2025
Basic computation	61,460,756	61,339,498
Dilutive effect of: Performance and restricted share awards(1)	171,246	86,603
Diluted computation	61,632,002	61,426,101

(1)Performance share awards are included in diluted weighted average number of shares outstanding based upon what would be issued if the end of the most recent reporting period was the end of the term of the award.

As of March 31, 2026, there were no shares from performance and restricted share awards which were antidilutive and excluded from the earnings per share calculations, compared to 49,071 shares as of March 31, 2025.

(10) Employee Benefit Plans

We sponsor and/or contribute to pension and postretirement health care and life insurance benefit plans for eligible employees. Net periodic benefit cost (credit) for our pension and other postretirement plans consists of the following (in thousands):

		Pension Benefits						Other Postretirement Benefits
	Three Months Ended March 31,							Three Months Ended March 31,
	2026				2025			2026			2025
Components of Net Periodic Benefit Cost (Credit)
Service cost	$	1,098		$	1,195		$	54		$	62
Interest cost		2,891			6,045			102			127
Expected return on plan assets		(2,923)			(5,742)			(403)			(354)
Recognized actuarial loss (gain)		—			—			(161)			(70)
Net periodic benefit cost (credit)	$	1,066		$	1,498		$	(408)		$	(235)

We contributed $2.0 million to our pension plans during the three months ended March 31, 2026. We expect to contribute an additional $9.5 million to our pension plans during the remainder of 2026.

(11) Commitments and Contingencies Parent Guarantee

NorthWestern Energy Group, Inc. has guaranteed the contractual obligations of its wholly-owned subsidiary, NorthWestern Colstrip 370Pu, LLC (NW Colstrip 370), to its counterparty to an agreement for the sale of capacity and energy from our recently acquired 370 megawatt ownership interest in the Colstrip facility. The guarantee exists during the January 2026 through September 2027 term of the agreement. The guarantee is unconditional and irrevocable, covering all payment obligations of the subsidiary under the contract up to a maximum amount of $15.0 million. The guarantee is triggered in an event where NW Colstrip 370 fails to pay any amounts that could come due under the agreement. As of March 31, 2026, no demand has been made under the guarantee and management believes that risk of material payment under this guarantee is remote.

ENVIRONMENTAL LIABILITIES AND REGULATION

The circumstances set forth in Note 20 - Commitments and Contingencies to the financial statements included in the NorthWestern Energy Group Annual Report on Form 10-K for the year ended December 31, 2025 appropriately represent, in all material respects, the current status of our environmental liabilities and regulation.

LEGAL PROCEEDINGS

We are subject to various legal proceedings, governmental audits and claims that arise in the ordinary course of business. In our opinion, the amount of ultimate liability with respect to these other actions will not materially affect our financial position, results of operations, or cash flows.

UNAUDITED PRO FORMA CONDENSED COMBINED CONSOLIDATED FINANCIAL INFORMATION

On August 18, 2025, Black Hills Corporation, a South Dakota corporation (“Black Hills” or the “Company”), entered into an Agreement and Plan of Merger (the “Merger Agreement”) with NorthWestern Energy Group, Inc., a Delaware corporation (“NorthWestern”) and River Merger Sub Inc., a Delaware corporation and direct wholly owned subsidiary of Black Hills (“Merger Sub”). The Merger Agreement, which has been unanimously approved by both the board of directors of Black Hills and the board of directors of NorthWestern, provides for an all-stock merger of Black Hills and NorthWestern upon the terms and subject to the conditions set forth therein.

The Merger Agreement provides for Merger Sub to merge with and into NorthWestern (the "Merger"), with NorthWestern continuing as the surviving entity and a direct wholly owned subsidiary of Black Hills, which would assume a new corporate name, Bright Horizon Energy Corporation, as the resulting parent company of the combined corporate group.

At the effective time of the Merger (the “Effective Time”), each share of common stock of NorthWestern, par value $0.01 per share (the "NorthWestern Common Stock", issued and outstanding as of immediately prior to the Effective Time will be converted into the right to receive 0.98 (the "Exchange Ratio") validly issued, fully paid and non-assessable shares of common stock of Black Hills, par value $1.00 per share (the "Black Hills Common Stock") (or cash in lieu of fractional shares thereof), in each case upon and subject to the terms and conditions of the Merger Agreement.

The following unaudited pro forma condensed combined financial statements, which have been prepared to give effect to the Merger in accordance with Article 11 of Regulation S-X and are limited to adjustments required by such rules, include adjustments for the following:

•certain reclassifications to conform the historical financial statement presentation of Black Hills and NorthWestern; and

•application of the acquisition method of accounting under the provisions of the Financial Accounting Standards Board (FASB) Accounting Standards Codification, which we refer to as ASC 805, “Business Combinations,” to reflect estimated merger consideration of approximately $4.6 billion in exchange for 100% of all outstanding NorthWestern Common Stock;

The unaudited pro forma financial information should be read, if at all, together with its accompanying notes and in conjunction with the following historical consolidated financial statements and accompanying notes of Black Hills and NorthWestern, referenced below. The pro forma financial statements of Black Hills have been derived from:

•the audited consolidated financial statements of Black Hills as of and for the year ended December 31, 2025 included in Black Hills’ Annual Report on Form 10-K for the fiscal year then ended;

•the unaudited consolidated financial statements of Black Hills as of and for the three months ended March 31, 2026 included in Black Hills’ Quarterly Report on Form 10-Q for the quarterly period then ended;

•the audited consolidated financial statements of NorthWestern for the year ended December 31, 2025, included in NorthWestern's Annual Report on Form 10-K for the fiscal year then ended, filed as Exhibit 99.1 to Black Hills' Form 8-K filed on February 19, 2026; and

•the unaudited consolidated financial statements of NorthWestern as of and for the three months ended March 31, 2026, included in NorthWestern's’ Quarterly Report on Form 10-Q for the quarterly period then ended, filed as Exhibit 99.1 to the Current Report on Form 8-K;

The unaudited pro forma combined condensed statement of income combine the Black Hills and NorthWestern historical consolidated income statements for the three months ended March 31, 2026 and year ended December 31, 2025, giving effect to the Merger as if it were completed on January 1, 2025. The unaudited pro forma combined condensed balance sheet as of March 31, 2026 gives effect to the Merger as if it were completed on that date.

The historical consolidated financial information has been adjusted in the unaudited pro forma financial statements to give effect to certain pro forma events that are directly attributable to the Merger and factually supportable. The unaudited pro forma financial statements do not reflect other potential effects of the Merger, such as anticipated cost savings (or associated costs to achieve such savings) from operating efficiencies or restructuring that could result from the Merger, the effect of any regulatory actions that may impact the pro forma financial statements following completion of the Merger or the effects of any changes in business or market conditions as a result of the Merger or otherwise.

The statements and related notes have been prepared for illustrative purposes only, based upon applicable rules of the Securities and Exchange Commission. The pro forma information does not purport to be indicative of what the combined company’s consolidated financial position or results of operations actually would have been had the Merger been completed as of the dates indicated. In addition, the unaudited pro forma combined condensed financial information does not purport to project the future financial position or operating results of the combined company. The pro forma adjustments, which are subject to uncertainties, are based on the information available at the time of the preparation of these pro forma financial statements and on the basis of certain assumptions and estimates.

Amounts in the unaudited pro forma financial information below may not foot due to immaterial rounding differences.

BLACK HILLS CORPORATION AND NORTHWESTERN ENERGY GROUP
UNAUDITED PRO FORMA CONDENSED COMBINED STATEMENT OF INCOME (LOSS)
FOR THE THREE MONTHS ENDED MARCH 31, 2026
	Black Hills Corporation Historical			NorthWestern Energy Group Historical			Presentation Reclass (Note 1)			Transaction Accounting Adjustments			Note 3	Pro Forma Condensed Combined
	(in millions, except per share amounts)
Revenue	$	781		$	498		$	—		$	—			$	1,278
Operating expenses:
Fuel, purchased power and cost of natural gas sold		338			146			—			—				484
Operations and maintenance		148			75			46			—				269
Administrative and general		-			46			(46	)		—				—
Depreciation and amortization		75			67			—			—				142
Taxes other than income taxes		18			50			—			—				69
Total operating expenses		579			384			—			—				962
Operating income		202			114			—			—				316
Other income (expense):
Interest expense, net		(52	)		(40	)		—			—				(92	)
Other income (expense), net		1			3			—			—				4
Total other income (expense)		(51	)		(37	)		—			—				(88	)
Income before income taxes		151			77			—			—				228
Income tax (expense)		(18	)		(14	)		—							(31	)
Net income		133			64			—			—				197
Net income attributable to non-controlling interest		(2	)		-			—			—				(2	)
Net income available for common stock	$	131		$	64		$	-		$	-			$	195
Earnings per share of common stock:
Earnings per share, Basic	$	1.74		$	1.03									$	1.43
Earnings per share, Diluted	$	1.73		$	1.03									$	1.43
Weighted average common shares outstanding:
Basic		75			61			-			(1	)	(A)		136
Diluted		76			62			-			(1	)	(A)		136

2

BLACK HILLS CORPORATION AND NORTHWESTERN ENERGY GROUP
UNAUDITED PRO FORMA CONDENSED COMBINED STATEMENT OF INCOME (LOSS)
FOR THE YEAR ENDED DECEMBER 31, 2025
	Black Hills Corporation Historical			NorthWestern Energy Group Historical			Presentation Reclass (Note 1)			Transaction Accounting Adjustments			Note 3	Pro Forma Condensed Combined
	(in millions, except per share amounts)
Revenue	$	2,310		$	1,611		$	—		$	—			$	3,921
Operating expenses:
Fuel, purchased power and cost of natural gas sold		832			410			—			—				1,241
Operations and maintenance		590			285			158			34		(B), (C)		1,067
Administrative and general		-			158			(158	)		—				—
Depreciation and amortization		284			250			—			—				533
Taxes other than income taxes		67			182			—			—				250
Total operating expenses		1,773			1,285			—			34				3,091
Operating income		538			326			—			(34	)			829
Other income (expense):
Interest expense, net		(200	)		(150	)		—			—				(351	)
Other income (expense), net		6			12			—			—				18
Total other income (expense)		(194	)		(138	)		—			—				(332	)
Income before income taxes		344			188			—			(34	)			497
Income tax benefit (expense)		(44	)		(6	)		—			6		(D)		(44	)
Net income		300			181			—			(28	)			453
Net income attributable to non-controlling interest		(8	)		-			—			—				(8	)
Net income available for common stock	$	292		$	181		$	—		$	(28	)		$	445
Earnings per share of common stock:
Earnings per share, Basic	$	3.99		$	2.95									$	3.34
Earnings per share, Diluted	$	3.98		$	2.94									$	3.33
Weighted average common shares outstanding:
Basic		73			61			—			(1	)	(A)		133
Diluted		73			62			—			(1	)	(A)		133

3

BLACK HILLS CORPORATION AND NORTHWESTERN ENERGY GROUP
UNAUDITED PRO FORMA CONDENSED COMBINED BALANCE SHEET
AS OF MARCH 31, 2026
	Black Hills Corporation Historical			NorthWestern Energy Group Historical			Presentation Reclass (Note 1)			Transaction Accounting Adjustments			Note 3	Pro Forma Condensed Combined
	(in millions)
ASSETS
Current assets:
Cash, restricted cash and equivalents	$	31		$	28		$	—		$	(33	)	(E)	$	26
Accounts receivable, net		383			199			—			—				583
Materials, supplies and fuel		147			134			—			—				281
Regulatory assets, current		123			103			—			—				226
Other current assets		104			49			—			—				153
Total current assets		788			513			—			(33	)			1,268
Total property, plant and equipment, net		8,394			6,794			—			—				15,188
Other assets:
Goodwill		1,300			368			—			1,550		(F)		3,217
Regulatory assets, non-current		252			774			—			—				1,025
Other assets, non-current		87			134			—			—				221
Total other assets, non-current		1,638			1,275			—			1,550				4,463
TOTAL ASSETS	$	10,820		$	8,583		$	—		$	1,517			$	20,920
LIABILITIES AND EQUITY
Current liabilities:
Accounts payable	$	211		$	122		$	—		$	—			$	333
Accrued liabilities		262			323			—			—				585
Regulatory liabilities, current		86			31			—			—				117
Notes payable		252			150			—			—				402
Current maturities of long-term debt		410			105			—			—				515
Total current liabilities		1,221			731			—			—				1,952
Long-term debt, net of current maturities		3,993			3,178			—			—				7,170
Deferred credits and other liabilities:
Deferred income tax liabilities, net		737			751			—			(98	)	(G)		1,389
Regulatory liabilities, non-current		490			685			—			—				1,175
Other deferred credits and other liabilities		353			330			—			—				683
Total deferred credits and other liabilities		1,580			1,765			—			(98	)			3,247
Equity:
Stockholders’ equity -
Black Hills common stock, additional paid-in capital and treasury stock		2,532			-			—			4,552		(H)		7,084
NorthWestern common stock, additional paid-in capital and treasury stock		-			1,996			—			(1,996	)	(H)		(0	)
Retained earnings		1,421			919			—			(946	)	(H)		1,393
Accumulated other comprehensive income (loss)		(8	)		(6	)		—			6		(H)		(8	)
Total stockholders’ equity		3,945			2,909			—			1,615				8,470
Non-controlling interest		82			-						—				82
Total equity		4,027			2,909			—			1,615				8,551
TOTAL LIABILITIES AND TOTAL EQUITY	$	10,820		$	8,583		$	—		$	1,517			$	20,920

4

NOTES TO THE UNAUDITED PROFORMA CONDENSED COMBINED FINANCIAL STATEMENTS

(1) BASIS OF PROFORMA PRESENTATION

The unaudited pro forma combined condensed statements of income combine the Black Hills and NorthWestern historical consolidated income statements for the three months ended March 31, 2026 and the year ended December 31, 2025, giving effect to the Merger as if it were completed on January 1, 2025. The unaudited pro forma combined condensed balance sheet as of March 31, 2026 gives effect to the Merger as if it were completed on that date.

Black Hills’ and NorthWestern’s historical financial statements were prepared in accordance with U.S. GAAP and presented in U.S. dollars. Certain reclassifications have been made to NorthWestern’s historical presentation in order to conform to Black Hills’ historical presentation, as presented within the column titled “Presentation Reclass” in the pro forma balance sheet. Black Hills has not identified all adjustments necessary to conform NorthWestern’s accounting policies to Black Hills’ accounting policies. Upon completion of the Merger, or as more information becomes available, Black Hills will perform a more detailed review of NorthWestern’s accounting policies. As a result of that review, differences could be identified between the accounting policies of the two companies that, when conformed, could have a material impact on the combined company’s financial information. Further, there were no material transactions and balances between Black Hills and NorthWestern as of and for the three months ended March 31, 2026 and year ended December 31, 2025.

The accompanying unaudited pro forma condensed combined financial statements and related notes were prepared using the acquisition method of accounting under the provisions of ASC 805, with Black Hills considered the acquirer of NorthWestern. ASC 805 requires, among other things, that the assets acquired and liabilities assumed in a business combination be recognized at their fair values as of the acquisition date. For purposes of the unaudited pro forma condensed combined balance sheet, the purchase consideration has been allocated to the assets acquired and liabilities assumed of NorthWestern based upon management’s preliminary estimate of their fair values as of March 31, 2026. Black Hills has not completed the valuation analysis and calculations in sufficient detail necessary to arrive at the required estimates of the fair market value of the NorthWestern assets to be acquired or liabilities assumed. Accordingly, NorthWestern's assets and liabilities are presented at their respective carrying amounts and should be treated as preliminary fair values. Any differences between the fair value of the consideration transferred and the fair value of the assets acquired and liabilities assumed will be recorded as goodwill. Accordingly, the purchase price allocation and related adjustments reflected in these unaudited pro forma condensed combined financial statements are preliminary and subject to revision based on a final determination of fair value.

The unaudited pro forma financial statements are presented for illustration only and do not reflect anticipated cost savings (or associated costs to achieve such savings) from operating efficiencies or restructuring that could result from the Merger. Further, the pro forma financial statements do not reflect the effect of any regulatory actions that may impact the proforma financial statements when the Merger is completed.

(2) PRELIMINARY PURCHASE PRICE ALLOCATION

At the Effective Time, each share of NorthWestern Common Stock, issued and outstanding as of immediately prior to the Effective Time will be converted into the right to receive 0.98 validly issued, fully paid and non-assessable shares of Black Hills Common Stock (or cash in lieu of fractional shares thereof), in each case upon and subject to the terms and conditions of the Merger Agreement. For purposes of the unaudited pro forma condensed combined balance sheet, the estimated merger consideration is based on the total NorthWestern Common Stock issued and outstanding as of April 24, 2026 and the closing price per share of Black Hills Common Stock on May 7, 2026.

Refer to the table below for preliminary calculation of estimated merger consideration:

	Amount in millions (except exchange ratio and price per share)
NorthWestern Common Stock issued and outstanding as of April 24, 2026		62
Exchange ratio		0.98
Black Hills Common Stock to be issued		60
Black Hills Common Stock price on May 7, 2026	$	75.22
Estimated value of Black Hills Common Stock to be issued to NorthWestern stockholders pursuant to the Merger Agreement	$	4,534
Estimated cash consideration attributable to the settlement of equity awards		7
Estimated equity consideration attributable to the settlement of equity awards		10
Estimated fair value of merger consideration	$	4,551

5

The cash and equity consideration attributable to the settlement of equity awards represents the estimated fair value of share-based compensation for NorthWestern’s vested and replaced awards related to pre-combination services. NorthWestern’s outstanding equity awards will vest or be replaced by Black Hills’ restricted stock equity awards in the manner specified in the Merger Agreement. The estimated fair value of estimated merger consideration will primarily depend on the market price of Black Hills Common Stock when the merger is consummated. The following table shows the effect of changes in Black Hills Common Stock price and the resulting impact on the estimated merger consideration (in millions, except per share data):

Stock Price Sensitivity	Black Hills Common Stock Price (Per Share)			Estimated fair value of merger consideration			Estimated Goodwill
As presented	$	75.22		$	4,551		$	1,918
10% increase		82.74			5,005			2,371
10% decrease	$	67.70		$	4,098		$	1,464

The preliminary estimated Merger consideration as shown in the tables above is allocated to the tangible assets acquired and liabilities assumed of NorthWestern based on their preliminary estimated fair values. As mentioned above in Note 1, Black Hills has not completed the valuation analysis and calculations in sufficient detail necessary to arrive at the required estimates of the fair market value of the NorthWestern assets to be acquired or liabilities assumed. Accordingly, assets acquired and liabilities assumed are presented at their respective carrying amounts and should be treated as preliminary fair values. The fair value assessments are preliminary and are based upon available information and certain assumptions, which Black Hills believes are reasonable under the circumstances. Actual results may differ materially from the assumptions within the unaudited pro forma condensed combined financial statements.

The following table sets forth a preliminary allocation of the estimated Merger consideration to the fair value of the identifiable tangible and intangible assets acquired and liabilities assumed of NorthWestern using NorthWestern’s unaudited consolidated balance sheet as of March 31, 2026, with the excess recorded to goodwill:

	Amount (in millions)
Preliminary fair value of estimated total Merger consideration	$	4,551
Assets
Cash, restricted cash and equivalents		28
Accounts receivable, net		199
Materials, supplies and fuel		134
Regulatory assets, current		103
Other current assets		49
Total property, plant and equipment, net		6,794
Regulatory assets, non-current		774
Other assets, non-current		134
Total assets excluding existing goodwill		8,215
Liabilities
Accounts payable		(122	)
Accrued liabilities		(323	)
Regulatory liabilities, current		(31	)
Notes payable		(150	)
Current maturities of long-term debt		(105	)
Long-term debt, net of current maturities		(3,178	)
Deferred income tax liabilities, net		(659	)
Regulatory liabilities, non-current		(685	)
Other deferred credits and other liabilities		(330	)
Total liabilities		(5,582	)
Less: Net assets		2,633
Goodwill	$	1,918

(3) TRANSACTION ACCOUNTING ADJUSTMENTS

The transaction accounting adjustments included in the Unaudited Pro Forma Condensed Combined Statement of Income (Loss) and the Unaudited Pro Forma Condensed Combined Balance Sheet are as follows:

(A)The pro forma basic and diluted earnings per share calculations are based on the basic and diluted weighted average shares of Black Hills plus shares issued as part of the Merger. The pro forma basic and diluted weighted average shares outstanding are a combination of historical weighted average shares of Black Hills Common Stock and the share impact as part of the Merger. The effect of converting certain equity awards held by NorthWestern employees into Bright Horizon Energy Corporation Common Stock is not considered material to the pro forma weighted average number of basic and diluted shares outstanding. Weighted average shares outstanding are as follows:

6

Pro forma weighted average shares (in millions)	Three Months ended March 31, 2026
Historical Black Hills weighted average shares outstanding - basic		75
Black Hills common shares to be issued pursuant to the Merger Agreement (Note 2)		60
Pro forma weighted average shares - basic		136
Historical Black Hills weighted average shares outstanding - diluted		76
Black Hills common shares to be issued pursuant to the Merger Agreement (Note 2)		60
Pro forma weighted average shares - diluted		136

(B)Reflects estimated transaction-related costs of $26 million directly attributable to the merger, including investment banking fees, legal fees, consulting fees, and other transaction costs to be incurred by Black Hills. The adjustment was assumed to be recorded as Operation and maintenance expense on January 1, 2025. These non-recurring expenses are not anticipated to affect these Unaudited Pro Forma Condensed Combined Statements of Income (Loss) beyond twelve months after the closing date. For the three months ended March 31, 2026, Black Hills and NorthWestern incurred transaction costs of approximately $3 million and $2 million, respectively, directly attributable to the merger. For the year ended December 31, 2025, Black Hills and NorthWestern incurred transaction costs of approximately $10 million and $9 million, respectively, directly attributable to the merger.

(C)Represents a non-recurring adjustment of $8 million for the acceleration of Black Hills' equity awards subject to preexisting change-in-control provisions that will become immediately vested upon the closing of the Merger. This $8 million is considered a transaction-related cost in addition to the amount described in (B). The adjustment was assumed to be recorded as Operation and maintenance expense on January 1, 2025. This adjustment will not have a continuing impact to the Unaudited Pro Forma Condensed Combined Statements of Income (Loss) beyond twelve months after the closing date.

(D)Reflects $6 million for the income tax effects of pro forma adjustments in (B) and (C) above at the estimated combined statutory federal and state rate at 23%. For tax purposes related to adjustment (B) above, it is estimated that $18 million of transaction-related merger costs will be deductible and $8 million will be subject to capitalization.

(E)Reflects the payment of $26 million for Black Hills estimated transaction-related merger costs. Also reflects payment of $7 million for the settlement of certain NorthWestern's outstanding Restricted Stock Unit awards granted prior to signing of the Merger Agreement that will become immediately vested upon the closing of the Merger.

(F)Reflects an adjustment to goodwill based on the preliminary purchase price allocation discussed in Note 2 above:

	Amount (in millions)
Fair value of consideration transferred in excess of the preliminary fair value of assets acquired and liabilities assumed (Note 2)	$	1,918
Removal of NorthWestern's historical goodwill		(368	)
Pro forma net adjustment to goodwill	$	1,550

(G)Reflects an adjustment to deferred tax liabilities, net to remove $92 million of Northwestern's existing deferred tax liability related to goodwill and $6 million for the income tax effects of pro forma adjustments as described in (D) above.

(H)Reflects adjustments to Black Hills and NorthWestern equity based on the following:

	Black Hills common stock, additional paid-in capital and treasury stock			NorthWestern common stock, additional paid-in capital and treasury stock			Retained Earnings			Accumulated other comprehensive income (loss)				Total
Estimated value of Black Hills common shares to be issued to NorthWestern stockholders pursuant to the Merger Agreement	$	4,534		$	-		$	-		$	-			$	4,534
Removal of NorthWestern's historical stockholders' equity	$	-		$	(1,996	)	$	(919	)	$	6			$	(2,909	)
Estimated equity consideration attributable to the settlement of NorthWestern's equity awards	$	10		$	-		$	-		$	-			$	10
Adjustment for Black Hills estimated merger transaction costs, net of tax	$	-		$	-		$	(21	)	$	-			$	(21	)
Settlement of Black Hills' equity awards, net of tax	$	8					$	(6	)	$	-			$	2
Total	$	4,552		$	(1,996	)	$	(946	)	$	6			$	1,615

7

FAQ

What merger is Black Hills Corporation (BKH) pursuing with NorthWestern Energy Group?

Black Hills is pursuing an all-stock merger with NorthWestern Energy Group. NorthWestern will merge into a Black Hills subsidiary, becoming a wholly owned unit of a new parent, Bright Horizon Energy, subject to regulatory approvals and satisfaction of other conditions.

What is the share exchange ratio in the Black Hills–NorthWestern merger?

Each share of NorthWestern common stock will be converted into the right to receive 0.98 shares of Black Hills common stock. Fractional shares will be settled in cash, and the exchange is governed by the terms and conditions in the Merger Agreement.

How large is the estimated consideration for the Black Hills and NorthWestern merger?

The estimated merger consideration is about $4.55 billion, based on 62 million NorthWestern shares, an exchange ratio of 0.98, and a Black Hills share price of $75.22. This amount includes stock issued plus cash and equity for NorthWestern equity awards.

What pro forma financial impact does the merger show for Black Hills (BKH)?

Pro forma combined results for the quarter ended March 31, 2026 show revenue of $1.278 billion and net income available to common stock of $195 million. Pro forma basic earnings per share would have been $1.43, illustrating the scale of the combined utility platform.

Which regulatory approvals are required for the Black Hills–NorthWestern merger to close?

The merger requires approvals from the Federal Energy Regulatory Commission and several state commissions, including Montana, Nebraska and South Dakota. It also depends on absence of prohibitive court or regulatory orders and satisfaction of various tax, listing and covenant conditions.

How does the filing describe goodwill from the Black Hills and NorthWestern transaction?

Preliminary estimates allocate about $1.918 billion of the merger consideration to goodwill. This reflects the excess of consideration over the preliminary fair value of NorthWestern’s identifiable net assets, using carrying values as a proxy until final valuations are completed.

Filing Exhibits & Attachments

3 documents

Press Releases

• EX-99.1 NWE Q1 2026 10-Q 1.0 MB
• EX-99.2 PROFORMA STATEMENTS 825.8 KB

Other Documents

• EX-101 XBRL TAXONOMY EXTENSION SCHEMA WITH EMBEDDED LINKBASES DOCUMENT 30.1 KB