NorthWestern Energy Group Inc

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

SCHEDULE 14A

Proxy Statement Pursuant to Section 14(a) of

the Securities Exchange Act of 1934 (Amendment No. )

NorthWestern Energy Group, Inc.

(Name of Registrant as Specified In Its Charter)

(Name of Person(s) Filing Proxy Statement, if other than the Registrant)

2025 ANNUAL MEETING OF SHAREHOLDERS

March 12, 2025

Dear Fellow Shareholder:2024 was another great year of progress and purpose at NorthWestern Energy. We faced challenges and seized opportunities with the same resolve that’s been at the heart of our company for more than a century, and remain focused on striking the right balance between reliability, affordability, and sustainability. We are, and always will be, committed to delivering safe, reliable, and innovative energy solutions that create value for our customers, communities, employees, and you, our shareholders. As a shareholder, we encourage you to read this proxy statement, vote on the proposals before you, and attend the virtual annual meeting. The 2025 Virtual Annual Meeting of Shareholders will be held on Wednesday, April 30, 2025, at 10:00 a.m. Central at www.virtualshareholdermeeting.com/NWE2025. YOUR VOTE COUNTS. Whether or not you plan to attend the virtual annual meeting, we encourage you to vote promptly via internet, telephone, or mail.Thank you for your continued support of NorthWestern Energy.

Proxy Summary

Items of Business

2024 Executive Pay Overview

Alignment of Pay with Shareholder and Customer Interests

Our executive pay program is designed to align the long-term interests of our executives, shareholders, and customers. The program consists of three core components (base salary, annual cash incentive, and long-term equity incentive), which did not change in 2024. Our annual and long-term incentives continue to be performance-based, and our long-term equity incentive awards continue to be split 70/30 between performance share units with a three-year performance period and restricted share units with a three-year restricted period. As previously disclosed, in 2024 we replaced the executive retirement equity awards that we discontinued in 2022 with a more traditional supplemental executive retirement contribution. These changes better align our executive pay program with our peers and the market. The full design of our compensation program and its components are detailed in the Compensation Discussion and Analysis, beginning on page 32.

The performance-based incentive awards and time-based equity award place asignificant percentage of executive compensation at risk — approximately 80 percent of the compensation of our chief executive officer (CEO) and roughly 60 percent of the compensation of our other named executive officers (NEOs). Our Board establishes the metrics and targets for these incentive awards based on advice from the Compensation Committee’s independent compensation consultant, Towers Watson. The 2024 LTIP performance metrics did not change from 2023, although we did update the targets associated with those metrics.

We also require our executives to retain meaningful ownership of our stock (ranging from 2x to 6x their annual base salary). This structure encourages our executives to focus on both short- and long-term performance and rewards our executives, shareholders, and customers when we achieve our financial and operating objectives. We believe our compensation program is fair to all employees, as evidenced by our relatively low CEO to median employee pay ratio for 2024 of 34:1. For 2023, the average CEO to median employee pay ratio for our peers was 44:1, ranging from 22:1 to 74:1.

Performance Against Incentive Targets

We believe 2024 was critical in setting the stage for future growth for our Company. We filed general rate reviews in Montana, Nebraska, and South Dakota, settling the South Dakota rate review during the fourth quarter of the

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Proxy Summary

year. Rate reviews allow us to recover the cost of providing safe, reliable service, while contributing to earnings growth and achieving our financial objectives, which allows us to continue to invest in our system to the benefit of customers and shareholders. Other milestones include the completion of the Yellowstone County Generating Station and announcement of the future acquisition of additional ownership interests in the Colstrip Generating Station (with a zero-dollar purchase price), both of which will improve our generation capacity. We also made substantial progress on implementing our wildfire mitigation plan, including public safety power shutoff procedures, to help protect our important infrastructure and keep our customers safe. In addition, from a growth perspective, we announced the opportunity to serve two large-load data center customers.

From a financial perspective, our net income increased from the prior year, and, for the three-year period ended December 31, 2024, we achieved an ROAE of 7.5 percent, an EPS growth rate of 0.9 percent, and our TSR was 6.7 percent (as calculated for our long-term incentive awards). Operationally, we worked safely and provided highly reliable service to our customers. Additionally, our customer satisfaction performance exceeded target. In total, we achieved above target performance for our 2024 annual incentive awards and below target performance for our long-term incentive awards that vested in 2024. We provide further details regarding these awards and how performance is calculated in the Compensation Discussion and Analysis.

Shareholder Feedback on Executive Pay

At our 2024 virtual annual meeting, shareholders approved our 2023 NEO pay by 98.9 percent of the votes cast. In light of this overwhelming approval, we continue to operate within the same general parameters our shareholders previously approved, with the limited exceptions highlighted above and discussed in this Proxy Statement.

Pay Versus Performance

Based on the information in ourpay versus performance disclosure, beginning onpage 59, the CAP (compensation actually paid) to our CEO and other NEOs in 2024 was more than the compensation disclosed in the Summary Compensation Table. CAP appears to correlate with certain measures of corporate performance — CAP appears to increase or decrease with increased or decreased TSR, which is not surprising as a third of our LTIP awards are tied to relative TSR. However, CAP does not appear to correlate with certain other measures of corporate performance — CAP increased and decreased from year to year even though net income consistently increased, and our supplemental Company selected metric (three-year ROAE) remained relatively flat. This result also is not surprising because these metrics represent a smaller percentage of our incentive compensation.

Corporate Governance Overview

Corporate Governance is a pillar at NorthWestern Energy Group, Inc., and we believe our governance practices are sound, as demonstrated by our ranking from Moody’s Investor Service as the 5th best utility for governance practices. We provide details of our governance practices in the Corporate Governance section of this proxy statement.

We are nominating nine individuals for election as director, eight of whom were elected by shareholders at last year’s annual meeting by an average of 99.4 percent of the votes cast. Each of the nominees is independent, with the sole exception of our CEO. We consider our Board to be diverse from several perspectives (including four female and two ethnic minority nominees), as detailed in thebiographies of our nominees provided later in this proxy statement.

Our Board is led by an independent chair, and our four Board committees – Audit, Compensation, Governance, and Operations – are chaired by and composed entirely of independent directors.

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Items of Business

Proposal No. 1

Election of Directors

Our Board is nominating nine people for election as directors at the 2025 annual meeting. All nominees currently serve as a director of our Board. Elected directors will serve for one year, until the next annual meeting of shareholders (or until a successor is able to serve). Our diverse slate of nominees is listed below, and we provide additional background information and individual qualifications for each nominee in the Corporate Governance—Individual Directors section of this proxy statement, beginning onpage 19.

The Board of Directors recommends you vote “FOR” each of the nine director nominees.

Unless you specifically withhold your authority to vote for the election of directors, the persons named in the accompanying proxy intend to vote “FOR” the election of each of the following director nominees:

All nominees have advised the Board that they are able and willing to serve as a director. Although not anticipated, if any nominee becomes unavailable for any reason, the shares represented by the proxies may be voted for such

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Items of Business

other person or persons as may be determined by the holders of the proxies (unless a proxy contains instructions to the contrary). In no event will the proxy be voted for more than nine nominees.

Board Nomination Process

Our Governance Committee leads the Board in a director succession planning process to allow for a smooth and gradual transition from our longer tenured directors, while preserving the culture of the Board. This process includes a review of individual skill sets and tenures of current members and considers additional attributes that could be beneficial for the Board in the future, with a particular focus on Company strategy, emerging risks, and a diversity of perspectives.

Our Board relied on this succession process, when Mr. Clark announced in early August 2024 that he would be resigning from the Board at the end of 2024 (see below, Thanking a Former Board Member). With the pending departure, the Board identified the need for additional utility and CEO expertise, and, after considering several qualified candidates, invited David Goodin to join the Board, effective December 1, 2024, to serve until our next annual meeting.

When selecting the current slate of nominees, the Board concluded the nominees bring a diverse and extensive professional experience providing a broad collective skill set that is advantageous to the oversight of the Company. While the industry-specific expertise possessed by certain of the nominees is essential, we also will benefit from the viewpoints of directors with expertise outside our industry which expand the Board’s ability to provide relevant guidance to our business.

Our Board recommends a vote “FOR” election of each of the nominees.

Directors will be elected by a favorable vote of a plurality of the shares present online at the virtual annual meeting or represented by proxy and entitled to vote at the virtual annual meeting. You may vote “FOR” all of the nominees, or you may “WITHHOLD AUTHORITY” for one or more of the nominees. Withheld votes will not count as votes cast for the nominee but will count for purposes of determining whether a quorum is present. Shareholders do not have the right to cumulate their vote for directors. If your shares are held through a broker, bank, or other nominee and you do not vote your shares, your bank, broker, or other nominee may not vote your shares in this proposal, as it is considered a “non-routine” matter. Abstentions or broker non-votes as to the election of directors will not affect the election of the candidates receiving a plurality of votes; however, under our Majority Plus Resignation Vote Policy described onpage 24 of this proxy statement, if a nominee for director receives more “WITHHOLD AUTHORITY” votes than “FOR” votes, such nominee shall immediately tender his or her resignation under the procedures in the policy.

Thanking a Former Board Member

After serving on our Board for eight years, Tony Clark announced he would resign effective December 31, 2024, as he transitioned to the role of Executive Director of the National Association of Regulatory Utility Commissioners. During his time on our Board, Mr. Clark served on the Governance Committee (including as its chair), the Compensation Committee, and the Operations Committee. As a respected state and federal utility regulator and a leading voice regarding transmission markets, his guidance has been invaluable to both our Company and shareholders. We wish him well in his new role and are grateful to have had his service on our Board.

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Items of Business

Proposal No. 2

Ratification of Deloitte & Touche LLP as the Independent Registered Public Accounting

Firm for 2025

Our Audit Committee oversees the integrity of our accounting, financial reporting, and auditing processes. To assist with these responsibilities, the Audit Committee has appointed Deloitte as our independent registered public accounting firm to audit our financial statements for 2025. The Board is asking you to ratify the committee’s decision at the annual meeting. The Board values your input on the committee’s appointment of Deloitte, but approval by shareholders is not required by law. If shareholders do not ratify the appointment of Deloitte, the committee will reconsider its selection. Regardless of the voting result, the committee may appoint a new firm at any time if it believes a change would be in the best interests of the Company and its shareholders.

The Board of Directors recommends you vote “FOR” the ratification of Deloitte & Touche LLP as the independent registered public accounting firm for 2025.

Deloitte representatives will be present at the annual meeting. They will have the opportunity to make a statement if they desire to do so and are expected to be available to respond to appropriate questions.

Description of Audit Fees

The table below presents a summary of the fees paid to Deloitte for professional services for the fiscal years ended December 31, 2023, and 2024.

Audit-related feesare fees billed for assurance and related services that are reasonably related to the performance of the audit of our financial statements and are not reported under “Audit Fees.”

Tax feesare fees billed for tax compliance, tax advice, and tax planning.

All other fees are fees for products and services other than the services reported above.

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Items of Business

Pre-approval Policies and Procedures

SEC rules require public company audit committees to pre-approve audit and non-audit services. Our Audit Committee follows procedures pursuant to which audit, audit-related, tax, and all permissible non-audit services are pre-approved by category of service. The fees are budgeted, and actual fees versus the budget are monitored throughout the year. Circumstances may arise when it becomes necessary to engage the independent public accountants for additional services not contemplated in the pre-approved budget. In those instances, we obtain pre-approval of the Audit Committee before engaging independent public accountants. The procedures require the Audit Committee to be informed of each service, and the procedures do not include any delegation of the Audit Committee’s responsibilities to management. The Audit Committee may delegate pre-approval authority to one or more of its members; the member to whom such authority is delegated will report any pre-approval decisions to the Audit Committee at its next scheduled meeting.

Pursuant to the provisions of the Company’s Audit Committee Charter, before Deloitte is engaged to render audit or non-audit services, the Audit Committee must pre-approve such engagement. For 2024, the Audit Committee (or the Chair of the Audit Committee pursuant to delegated authority) pre-approved 100 percent of the audit, audit-related, tax, and other fees.

Leased Employees

In connection with their audit of our 2024 annual financial statements, more than 50 percent of Deloitte’s work was performed by full-time, permanent employees of Deloitte.

The affirmative vote of the holders of a majority of the shares present online at the virtual annual meeting or represented by proxy and entitled to vote at the virtual annual meeting is required to ratify the appointment of Deloitte as our independent registered public accounting firm for 2025. If voting instructions are not provided, brokers may vote a client’s proxy in their own discretion on this proposal, as it is considered a “routine” matter. Abstentions will have the same effect as a vote against the proposal. Unless instructed to the contrary in the proxy, the shares represented by the proxies will be voted “FOR” the proposal to ratify the selection of Deloitte to serve as the independent registered public accounting firm for NorthWestern Energy for the fiscal year ending December 31, 2025.

Audit Committee Report

In the performance of the Audit Committee’s oversight function, and in connection with the December 31, 2024, financial statements, the Audit Committee reviewed and discussed the audited financial statements with management and Deloitte. It discussed the matters required by the applicable requirements of the PCAOB and the SEC. The Audit Committee received the written disclosures and the letter from Deloitte, our independent registered public accounting firm, required by applicable requirements of the PCAOB regarding the independent accountant’s communications with the Audit Committee concerning independence; and it has discussed with Deloitte the firm’s independence. The Audit Committee considered the compatibility of non-audit services in connection with the auditor’s independence.

Based on the Audit Committee’s review of the consolidated financial statements and discussions with and representations from management and Deloitte referred to above, it recommended to the Board that the audited financial statements be included in our Annual Report on Form 10-K for the year ended December 31, 2024, filed with the SEC.

Audit Committee

Jeffrey Yingling, Chair Dave Goodin

Jan Horsfall Kent Larson

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