Exhibits 5.1 and 23.1 Company Counsel Opinion and Consent

October 2, 2023

NorthWestern Energy Group, Inc.

3010 West 69th Street

Sioux Falls, South Dakota 57108    

Re:    Registration Statement on Form S-3 of NorthWestern Energy Group, Inc.

Ladies and Gentlemen:

I serve as Senior Corporate Counsel and Corporate Secretary of NorthWestern Energy Group, Inc., a Delaware corporation (the “Company”), and in such capacity I, or the attorneys that I supervise, have acted as counsel to the Company in connection with the Registration Statement on Form S-3 (as the same may be amended from time to time, the “Registration Statement”) to be filed by the Company with the Securities and Exchange Commission (the “Commission”) under the Securities Act of 1933 (the “Securities Act”) for the registration of an unspecified amount of: (i) shares of common stock, par value $0.01 per share, of the Company (the “Common Stock”); (ii) shares of preferred stock, par value $0.01 per share, of the Company (the “Preferred Stock”), in one or more series, certain of which may be convertible into or exchangeable for Common Stock; (iii) depositary shares representing fractional interests in Preferred Stock, in one or more series (the “Depositary Shares”); and (iv) one or more series of unsecured debt securities (the “Debt Securities”), in each case as contemplated by the Registration Statement. The Common Stock, the Preferred Stock, the Depositary Shares and the Debt Securities are collectively referred to herein as the “Securities” and each, a “Security.” The Securities are to be issued from time to time pursuant to Rule 415 under the Securities Act.

As part of the corporate action taken and to be taken in connection with the issuance of the Securities (the “Corporate Proceedings”), certain terms of the Securities to be issued by the Company from time to time will be approved by the Company’s Board of Directors or a committee thereof or certain authorized officers of the Company.

In connection with the opinions expressed herein, I have examined such documents, records and matters of law as I have deemed relevant or necessary for purposes of such opinions. Based on the foregoing, and subject to the further limitations, qualifications and assumptions set forth herein, I am of the opinion that:

1.    The Company is a validly organized and legally existing corporation, in good standing under the laws of the State of Delaware, and is authorized to conduct and operate its business in the States of Montana, Nebraska, and South Dakota.

2.    The shares of Common Stock, upon registration and delivery of such shares and receipt by the Company of consideration therefor, in the manner contemplated by the Registration Statement, will be validly issued, fully paid and nonassessable.

3.    The shares of Preferred Stock, upon registration and delivery of such shares and receipt by the Company of consideration therefor, in the manner contemplated by the Registration Statement, will be validly issued, fully paid and nonassessable.

4.    The Depositary Shares, upon delivery of such shares and receipt by the Company of consideration therefor, in the manner contemplated by the Registration Statement, will be validly issued, and the depositary receipts representing the Depositary Shares will entitle the holders thereof to the rights specified therein and in the deposit agreement pursuant to which they are issued.

Exhibits 5.1 and 23.1 Company Counsel Opinion and Consent

5.    The Debt Securities, upon (i) due authorization, execution and delivery of an indenture and/or a supplemental indenture with respect to the Debt Securities in accordance with the terms thereof (the “Indenture”), (ii) the Board of Directors of the Company, and officers duly authorized thereby, having taken such action, pursuant to the terms of the Indenture, as may be necessary to establish the terms of the Debt Securities, and the issuance, delivery and authentication of the Debt Securities in accordance with the terms and provisions of the Indenture, and (iii) issuance and delivery of such Debt Securities and receipt of consideration therefor as contemplated in the Registration Statement and a prospectus supplement with respect thereto, the Debt Securities will be legally issued and valid and binding obligations of the Company.

In rendering the foregoing opinions, I have assumed that: (i) the Registration Statement, and any amendments thereto, will have become effective (and will remain effective at the time of issuance of any Securities thereunder); (ii) a prospectus supplement describing each class and/or series of Securities offered pursuant to the Registration Statement, to the extent required by applicable law and relevant rules and regulations of the Commission, will be timely filed with the Commission; (iii) the Corporate Proceedings authorizing the issuance and sale of such Securities will have been adopted by the Company’s Board of Directors or an authorized committee thereof and will be in full force and effect at all times at which the Securities are offered or sold by the Company, and that the issuance of such Securities will not violate any issuance limitation contained in such Corporate Proceedings; (iv) the definitive terms of each class and/or series of Securities will have been established in accordance with the Corporate Proceedings and, as applicable, the Company’s Amended and Restated Certificate of Incorporation and applicable law; (v) the Company will issue and deliver the Securities in the manner contemplated by the Registration Statement and any Securities that consist of shares of capital stock will have been authorized and reserved for issuance, in each case within the limits of the then remaining authorized but unissued and unreserved amounts of such capital stock; (vi) any Deposit Agreement (as defined below), or supplement thereto, will constitute a valid and binding obligation of each party thereto other than the Company and (viii) the Indenture will constitute a valid and binding obligation of each party thereto other than the Company.

With respect to any Securities consisting of Preferred Stock, I have further assumed that the Company will issue and deliver the shares of Preferred Stock being issued and delivered after the filing with the Secretary of State of the State of Delaware of a certificate of amendment to the Company’s Amended and Restated Certificate of Incorporation and/or a certificate of designations establishing the designations, preferences and rights of the class or series of Preferred Stock being issued and delivered.

With respect to any Securities consisting of Depositary Shares, I have further assumed that the Depositary Shares will be: (i) issued and delivered after authorization, execution and delivery of a deposit agreement relating to the Depositary Shares to be entered into between the Company and an entity (the “Depositary”) selected by the Company to act as depositary (the “Deposit Agreement”), and (ii) issued after the Company deposits with the Depositary shares of the Preferred Stock to be represented by such Depositary Shares that are authorized, validly issued, fully paid and nonassessable as contemplated by the Registration Statement and the Deposit Agreement.

The opinions expressed herein are limited by bankruptcy, insolvency, reorganization, fraudulent transfer and fraudulent conveyance, voidable preference, moratorium or other similar laws and related regulations and judicial doctrines from time to time in effect relating to or affecting creditors’ rights generally, and by general equitable principles and public policy considerations, whether such principles and considerations are considered in a proceeding at law or equity.

As to facts material to the opinions and assumptions expressed herein, I have relied upon oral or written statements and representations of officers and other representatives of the Company and others. The opinions expressed herein are limited to the laws of the State of South Dakota and the Delaware General Corporation Law, including applicable provisions of the Delaware Constitution and the reported

Exhibits 5.1 and 23.1 Company Counsel Opinion and Consent

judicial decisions interpreting such law, in each case as currently in effect, and I express no opinion as to the effect of the laws of any other jurisdiction.

I hereby consent to the filing of this opinion as Exhibit 5.1 to the Registration Statement and to the reference with respect to this opinion under the caption “Legal Opinions” in the prospectus constituting a part of the Registration Statement. In giving such consent, I do not thereby admit that I am included in the category of persons whose consent is required under Section 7 of the Securities Act or the rules and regulations of the Commission promulgated thereunder.

Sincerely,

/s/ Timothy P. Olson

Timothy P. Olson

Senior Corporate Counsel & Corporate Secretary

NorthWestern Energy Group, Inc.