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We are issuing this opinion in our capacity as special counsel to Talen Energy Corporation, a Delaware corporation (the “Company”), in connection with the preparation of the Registration Statement on Form S-3 (such Registration Statement, as amended or supplemented, is hereinafter referred to as the “Registration Statement”) filed with the U.S. Securities and Exchange Commission (the “Commission”) on or about August 7, 2025 under the Securities Act of 1933, as amended (the “Securities Act”), by the Company. The Registration Statement relates to the issuance and sale from time to time, pursuant to Rule 415 of the General Rules and Regulations promulgated under the Securities Act, of an unspecified amount of the following securities: (i) senior debt securities issued by the Company (the “Senior Debt Securities”), (ii) subordinated debt securities issued by the Company (the “Subordinated Debt Securities” and, together with the Senior Debt Securities, the “Debt Securities”), (iii) preferred stock of the Company (the “Preferred Stock”), (iv) warrants to purchase the Preferred Stock (the “Preferred Warrants”), (v) common stock of the Company (the “Common Stock”) and (vi) warrants to purchase the Common Stock (the “Common Warrants” and, together with the Preferred Warrants, the “Warrants”); (vii) units consisting of one or more shares of Debt Securities, Preferred Stock, Common Stock, Warrants or any combination of such securities (“Units”); and (viii) subscription rights to purchase Debt Securities, Preferred Stock, Common Stock, Warrants or Units (the “Rights”). The Rights, together with the Debt Securities, the Preferred Stock, the Common Stock, Warrants and Units are collectively referred to as the “Securities,” which the Company may offer from time to time in one or more classes or series and in amounts on a delayed or continuous basis. Any Debt Securities and Preferred Stock may be convertible into or exchangeable for Common Stock or other Securities.

You have advised us that: (i) the Debt Securities will be issued under the indenture (as amended or supplemented from time to time, the “Indenture”) between the Company and a financial institution to be identified therein as the trustee (the “Trustee”); (ii) the Common Warrants will be issued under one or more common warrant agreements (each, a “Common Warrant Agreement”); (iii) the Preferred Warrants will be issued under one or more preferred warrant agreements (each, a “Preferred Warrant Agreement” and, together with the Common Warrant Agreements, the “Warrant Agreements”) each to be between the Company and a financial institution identified therein as warrant agent (each, a “Warrant Agent”); (iv) the Units will be issued under one or more unit agreements (each, a “Unit Agreement”), each to be between the Company and a financial institution identified therein as the depositary (the “Depositary”); and (v) the Rights will be issued under one or more subscription rights agreements (each, a “Rights Agreements”), each to be between the Company and a financial institution identified therein as rights agent (the “Rights Agent”). The Indenture, each Warrant Agreement, each Unit Agreement and each Rights Agreement shall be referred to herein as a “Governing Document.” The Trustee, each Depositary and each Warrant Agent shall be referred to herein as a “Governing Document Counterparty.”

For purposes of this letter, we have examined originals, or copies certified or otherwise identified to our satisfaction, of such documents, corporate records and other instruments as we have deemed necessary for the purposes of this opinion, including: (i) the corporate and organizational documents of the Company, (ii) minutes and records of the corporate proceedings of the Company and (iii) the Registration Statement and the exhibits thereto.

For purposes of this letter, we have assumed the authenticity of all documents submitted to us as originals, the conformity to the originals of all documents submitted to us as copies and the authenticity of the originals of all documents submitted to us as copies. We have also assumed the legal capacity of all natural persons, the genuineness of the signatures of persons signing all documents in connection with which this opinion is rendered, the authority of such persons signing on behalf of the parties thereto other than the Company and the due authorization, execution and delivery of all documents by the parties thereto other than the Company. We have not independently established or verified any facts relevant to the opinions expressed herein, but have relied upon statements and representations of the officers and other representatives of the Company.

1.When the specific terms of any offering or offerings of Common Stock have been duly established by the Board of Directors of the Company or a committee thereof and in accordance with provisions of any applicable Purchase Agreement so as not to violate any applicable law or agreement or instrument then binding on the Company, and when certificates representing the shares of Common Stock have been duly executed, countersigned, registered and delivered against payment therefor in accordance with the applicable Purchase Agreement (which shall be in an amount at least equal to the par value of the shares being issued and sold) or upon exchange in accordance with the terms of any other Security that has been duly authorized, issued, paid for and delivered, such shares will be validly issued, fully paid and non-assessable.

2.Upon designation of the preferences and relative, participating, optional and other special rights, and qualifications, limitations or restrictions, of any series of Preferred Stock by the Board of Directors of the Company or a committee thereof and proper filing with the Secretary of State of the State of Delaware of a certificate of designations relating to such series of Preferred Stock, all necessary corporate action on the part of the Company will have been taken to authorize the issuance and sale of such series of Preferred Stock proposed to be sold by the Company, and when certificates representing the shares of Preferred Stock have been duly executed, countersigned, registered and delivered against payment therefor in accordance with the applicable Purchase Agreement (which shall be in an amount at least equal to the par value of the shares being issued and sold) or upon exchange in accordance with the terms of any other Security that has been duly authorized, issued, paid for and delivered, such shares will be validly issued, fully paid and non-assessable.

3.When, as and if (a) the terms of any particular series of Debt Securities have been duly authorized and duly established in accordance with the Indenture and applicable law, (b) the appropriate corporate or organizational action has been taken to authorize the form, terms, execution and delivery of such Debt Securities (and any required amendment or supplement to the Indenture), and (c) the applicable Debt Securities have been duly executed, attested, issued and delivered by duly authorized officers against payment in accordance with such authorization, the Indenture, the applicable Purchase Agreement and applicable law and authenticated by the Trustee, such Debt Securities (including any Debt Securities duly executed and delivered (i) upon the exchange or conversion of Debt Securities that are exchangeable or convertible into another series of Debt Securities or (ii) upon

4.When, as and if (a) the appropriate corporate action has been taken by the Company to authorize the form, terms, execution and delivery of the Warrant Agreement (including a form of certificate evidencing the Warrants), (b) Warrants with such terms have been duly executed, attested, issued and delivered by duly authorized officers of the Company against payment in accordance with such authorization, the applicable Purchase Agreement and applicable law, and (c) the Securities issuable upon exercise of such Warrants have been duly authorized and reserved for issuance by all necessary corporate or organizational action, such Warrants will constitute valid and binding obligations of the Company, enforceable against the Company in accordance with their terms.

5.When, as and if (i) any Units have been duly authorized and duly established in accordance with applicable law, (ii) the appropriate corporate action has been taken by the Company to authorize the form, terms, execution and delivery of the Units (including a form of certificate evidencing the Units) and the related Unit Agreement, (iii) the Units and the related Unit Agreement with such terms have been duly executed, attested, issued and delivered by duly authorized officers of the Company against payment therefor in accordance with such authorization and the applicable Unit Agreement, and (iv) the Securities issuable upon exercise of such Units and Unit Agreement have been duly authorized and reserved for issuance by all necessary corporate or organizational action, such Units and Unit Agreement will constitute valid and binding obligations of the Company, enforceable against the Company in accordance with their terms.

6.When the applicable Warrant Agreement or Rights Agreement has been duly authorized, executed and delivered by all necessary corporate action of the Company, and when the specific terms of a particular issuance of Warrants or Rights, as applicable, have been duly established in accordance with the terms of the applicable Warrant Agreement or Rights Agreement and authorized by all necessary corporate action of the Company, and such Warrants or Rights, as applicable, have been duly executed, authenticated, issued and delivered against payment therefor in accordance with the terms of the applicable Warrant Agreement or Rights Agreement and in the manner contemplated by the applicable Prospectus Supplement and by such corporate action (assuming the securities issuable upon exercise of such Warrants or Rights, as applicable, have been duly authorized by all necessary corporate action), such Warrants or Rights, as applicable, will be the legally valid and binding obligations of the Company, enforceable against the Company in accordance with their terms.

Our opinions expressed above are subject to the qualifications that we express no opinion as to the applicability of, compliance with, or effect of (i) any bankruptcy, insolvency, reorganization, fraudulent transfer, fraudulent conveyance, moratorium or other similar law affecting the enforcement of creditors’ rights generally, (ii) general principles of equity (regardless of whether enforcement is considered in a proceeding in equity or at law), (iii) public policy considerations which may limit the rights of parties to obtain certain remedies, and (iv) any laws except the laws of the State of New York and the General Corporation Law of the State of Delaware, including the applicable provisions of the Delaware constitution and reported judicial decisions interpreting these laws.

We express no opinion with respect to the enforceability of (i) consents to, or restrictions upon, judicial relief or jurisdiction or venue; (ii) waivers of rights or defenses with respect to stay, extension or usury laws; (iii) advance waivers of claims, defenses, rights granted by law, or notice, opportunity for hearing, evidentiary requirements, statutes of limitation, trial by jury or at law, or other procedural rights; (iv) waivers of broadly or vaguely stated rights; (v) provisions for exclusivity, election or accumulation of rights or remedies; (vi) provisions authorizing or validating conclusive or discretionary determinations; (vii) grants of setoff rights; (viii) provisions for the payment of attorneys’ fees where such payment is contrary to law or public policy; (ix) proxies, powers and trusts; (x) restrictions upon non-written modifications and waivers; (xi) provisions prohibiting, restricting, or requiring consent to assignment or transfer of any right or property; (xii) any provision to the extent it requires any party to indemnify any other person against loss in obtaining the currency due following a court judgment in another currency; and (xiii) provisions for liquidated damages, default interest, late charges, monetary penalties, make-whole premiums or other economic remedies to the extent such provisions are deemed to constitute a penalty. In addition, we express no opinion with respect to (i) whether acceleration of the Debt Securities may affect the collectability of that portion of the stated principal amount thereof that might be determined to constitute unearned interest thereon, (ii) compliance with laws relating to permissible rates of interest or (iii) the creation, validity, perfection or priority of any security interest or lien.

To the extent that the obligations of the Company under any Governing Document may be dependent on such matters, we assume for purposes of this opinion that the applicable Governing Document Counterparty is duly organized, validly existing and in good standing under the laws of its jurisdiction of organization; that the applicable Governing Document Counterparty is duly qualified to engage in the activities contemplated by the applicable Governing Document; that the applicable Governing Document has been duly authorized, executed and delivered by the applicable Governing Document Counterparty and constitutes the legally valid and binding obligations of such Governing Document Counterparty, enforceable against such Governing Document Counterparty in accordance with its terms; that the applicable Governing Document Counterparty is in compliance, generally and with respect to acting as trustee, warrant agent, depositary or other counterparty, as the case may be, under the applicable Governing Document, with all applicable laws and regulations; and that the applicable Governing Document Counterparty has the requisite organizational and legal power and authority to perform its obligations under the applicable Governing Document.

We hereby consent to the filing of this opinion with the Commission as Exhibit 5 to the Registration Statement. We also consent to the reference to our firm under the heading “Legal Matters” in the Registration Statement. In giving this consent, we do not thereby admit that we are in the category of persons whose consent is required under Section 7 of the Securities Act or the rules and regulations of the Commission.


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Talen Energy Corporation August 7, 2025 Page 2