[Letterhead of]<\/p>\n
CRAVATH, SWAINE & MOORE LLP <\/strong><\/p>\n [New York Office]<\/p>\n December 16, 2011<\/p>\n Alliant Energy Corporation <\/u><\/p>\n Registration Statement on Form S-3 <\/u><\/p>\n Ladies and Gentlemen:<\/p>\n We have acted as counsel for Alliant Energy Corporation, a Wisconsin Unless otherwise provided in any prospectus supplement forming a part of the In connection with this opinion, we have examined originals, or copies Based upon and subject to the foregoing, and assuming that (i) the 1. With respect to the Debt Securities to be issued under the Indenture, 2. With respect to the Warrants, when (A) the Board has taken all necessary 2<\/p>\n party thereto and (C) the Warrants or certificates representing the Warrants 3. With respect to the Stock Purchase Contracts, when (A) the Board has taken 4. With respect to the Stock Purchase Units, when (A) the Board has taken all 3<\/p>\n We express no opinion herein as to any provision of the Indenture or the Debt Courts in the United States have not customarily rendered judgments for money We are admitted to practice only in the State of New York and express no We are aware that we are referred to under the heading “Legal Matters” in the Very truly yours,<\/p>\n \/s\/ Cravath, Swaine & Moore LLP<\/p>\n<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n Alliant Energy Corporation<\/p>\n 4902 North Biltmore Lane<\/p>\n Madison, WI 53718<\/p>\n 4<\/p><\/p>\n","protected":false},"template":"","meta":{"_acf_changed":false,"_stopmodifiedupdate":true,"_modified_date":"","_cloudinary_featured_overwrite":false},"corporate_contracts_companies":[6631],"corporate_contracts_industries":[9534],"corporate_contracts_types":[9629],"class_list":["post-43835","corporate_contracts","type-corporate_contracts","status-publish","hentry","corporate_contracts_companies-alliant-energy-corp","corporate_contracts_industries-utilities__electric","corporate_contracts_types-securities"],"acf":[],"_links":{"self":[{"href":"https:\/\/corporate.findlaw.com\/legal-api\/wp-json\/wp\/v2\/corporate_contracts\/43835","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/corporate.findlaw.com\/legal-api\/wp-json\/wp\/v2\/corporate_contracts"}],"about":[{"href":"https:\/\/corporate.findlaw.com\/legal-api\/wp-json\/wp\/v2\/types\/corporate_contracts"}],"wp:attachment":[{"href":"https:\/\/corporate.findlaw.com\/legal-api\/wp-json\/wp\/v2\/media?parent=43835"}],"wp:term":[{"taxonomy":"corporate_contracts_companies","embeddable":true,"href":"https:\/\/corporate.findlaw.com\/legal-api\/wp-json\/wp\/v2\/corporate_contracts_companies?post=43835"},{"taxonomy":"corporate_contracts_industries","embeddable":true,"href":"https:\/\/corporate.findlaw.com\/legal-api\/wp-json\/wp\/v2\/corporate_contracts_industries?post=43835"},{"taxonomy":"corporate_contracts_types","embeddable":true,"href":"https:\/\/corporate.findlaw.com\/legal-api\/wp-json\/wp\/v2\/corporate_contracts_types?post=43835"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}
\ncorporation (the “Company”), in connection with the filing of the Registration
\nStatement on Form S-3 (the “Registration Statement”) with the Securities and
\nExchange Commission (the “Commission”) under the Securities Act of 1933, as
\namended (the “Securities Act”), relating to the registration under the
\nSecurities Act and the proposed issuance and sale from time to time pursuant to
\nRule 415 under the Securities Act of: (i) shares of common stock of the Company,
\n$.01 par value per share (the “Common Stock”), and related Common Share Purchase
\nRights (the “Rights”); (ii) debt securities of the Company, which may be
\nconvertible into Common Stock (the “Debt Securities”); (iii) warrants for the
\npurchase of Debt Securities, Common Stock or other securities (the “Warrants”);
\n(iv) stock purchase contracts as described in the Registration Statement (the
\n“Stock Purchase Contracts”); and (iv) stock purchase units as described in the
\nRegistration Statement (the “Stock Purchase Units”). The Common Stock and the
\nattached Rights, the Debt Securities, the Warrants, the Stock Purchase Contracts
\nand the Stock Purchase Units are referred to herein collectively as the “Offered
\nSecurities”.<\/p>\n
\nRegistration Statement relating to a particular series of the Debt Securities,
\nthe Debt Securities will be issued under an Indenture (the “Indenture”) dated
\nSeptember 30, 2009, between the Company and Wells Fargo Bank, National
\nAssociation, as trustee (the “Trustee”), filed as an exhibit to the Registration
\nStatement.<\/p>\n
\ncertified or otherwise identified to our satisfaction, of such corporate
\nrecords, certificates of corporate officers and government officials and such
\nother documents as we have deemed necessary or appropriate for the purposes of
\nthis opinion. As to various questions of fact material to this opinion, we have
\nrelied upon representations of officers or directors of the Company and
\ndocuments furnished to us by the Company without independent verification of
\ntheir accuracy. We have also assumed the genuineness of all signatures, the
\nauthenticity of all documents submitted to us as originals and the conformity to
\nauthentic original documents of all documents submitted to us as copies.<\/p>\n
\n
\nRegistration Statement and any supplements and amendments thereto (including
\npost-effective amendments) will have become effective and will comply with all
\napplicable laws; (ii) the Registration Statement will be effective and will
\ncomply with all applicable laws at the time the Offered Securities are offered
\nor issued as contemplated by the Registration Statement; (iii) a prospectus
\nsupplement will have been prepared and filed with the Commission describing the
\nOffered Securities offered thereby and will comply with all applicable laws;
\n(iv) all Offered Securities will be issued and sold in compliance with all
\napplicable Federal and state securities laws and in the manner stated in the
\nRegistration Statement and the appropriate prospectus supplement; (v) none of
\nthe terms of any Offered Security to be established subsequent to the date
\nhereof, nor the issuance and delivery of such Offered Security, nor the
\ncompliance by the Company with the terms of such Offered Security will violate
\nany applicable law or will result in a violation of any provision of any
\ninstrument or agreement then binding upon the Company or any restriction imposed
\nby any court or governmental body having jurisdiction over the Company; (vi) a
\ndefinitive purchase, underwriting or similar agreement and any other necessary
\nagreement with respect to any Offered Securities offered or issued will have
\nbeen duly authorized and validly executed and delivered by the Company and the
\nother parties thereto; and (vii) any Offered Securities issuable upon
\nconversion, exchange or exercise of any Offered Security being offered or issued
\nwill be duly authorized, created and, if appropriate, reserved for issuance upon
\nsuch conversion, exchange or exercise, we are of opinion as follows:<\/p>\n
\nassuming that the Company and the Trustee have duly authorized, executed and
\ndelivered the Indenture, when (A) the Trustee has been qualified to act as
\ntrustee under the Indenture, (B) the Indenture has been qualified under the
\nTrust Indenture Act of 1939, as amended, (C) the Board of Directors of the
\nCompany or a duly constituted and acting committee thereof (such Board of
\nDirectors or committee thereof being hereinafter referred to as the “Board”) has
\ntaken all necessary corporate action to approve the issuance and terms of a
\nparticular series of such Debt Securities, the terms of the offering thereof and
\nrelated matters, and (D) such Debt Securities have been duly executed,
\nauthenticated, issued and delivered in accordance with the provisions of the
\nIndenture and the applicable definitive purchase, underwriting or similar
\nagreement approved by the Board upon payment of the consideration therefor
\nprovided for therein, such Debt Securities will constitute valid and binding
\nobligations of the Company, enforceable against the Company in accordance with
\ntheir terms (subject to applicable bankruptcy, insolvency, reorganization,
\nfraudulent conveyance, moratorium or other similar laws affecting creditors’
\nrights generally from time to time in effect and subject to general principles
\nof equity, including concepts of materiality, reasonableness, good faith and
\nfair dealing, regardless of whether such enforceability is considered in a
\nproceeding in equity or at law).<\/p>\n
\ncorporate action to approve the creation of and the issuance and terms of the
\nWarrants, the terms of the offering thereof and related matters, (B) a warrant
\nagreement or agreements relating to the Warrants have been duly authorized and
\nvalidly executed and delivered by the Company, the warrant agent appointed by
\nthe Company and each other<\/p>\n
\n
\nhave been duly executed, countersigned, registered and delivered in accordance
\nwith the appropriate warrant agreement or agreements and the applicable
\ndefinitive purchase, underwriting or similar agreement approved by the Board
\nupon payment of the consideration therefor provided for therein, the Warrants
\nwill constitute valid and binding obligations of the Company, enforceable
\nagainst the Company in accordance with their terms (subject to applicable
\nbankruptcy, insolvency, reorganization, fraudulent conveyance, moratorium or
\nother similar laws affecting creditors’ rights generally from time to time in
\neffect and subject to general principles of equity, including concepts of
\nmateriality, reasonableness, good faith and fair dealing, regardless of whether
\nsuch enforceability is considered in a proceeding in equity or at law).<\/p>\n
\nall necessary corporate action to approve and establish the terms of the Stock
\nPurchase Contracts and to authorize and approve the issuance thereof, the terms
\nof the offering and related matters, (B) a purchase agreement or agreements
\nrelating to the Stock Purchase Contracts have been duly authorized and validly
\nexecuted and delivered by the Company and each other party thereto and (C) the
\nStock Purchase Contracts have been duly executed and delivered in accordance
\nwith the purchase agreement and the applicable definitive purchase, underwriting
\nor similar agreement approved by the Board upon payment of the consideration
\ntherefor provided for therein, the Stock Purchase Contracts will constitute
\nvalid and binding obligations of the Company, enforceable against the Company in
\naccordance with their terms (subject to applicable bankruptcy, insolvency,
\nreorganization, fraudulent conveyance, moratorium or other similar laws
\naffecting creditors’ rights generally from time to time in effect and subject to
\ngeneral principles of equity, including concepts of materiality, reasonableness,
\ngood faith and fair dealing, regardless of whether such enforceability is
\nconsidered in a proceeding in equity or at law).<\/p>\n
\nnecessary corporate action to approve and establish the terms of the Stock
\nPurchase Units and to authorize and approve the issuance thereof, the terms of
\nthe offering and related matters, (B) a purchase agreement or agreements
\nrelating to the Stock Purchase Units have been duly authorized and validly
\nexecuted and delivered by the Company and each other party thereto and (C) the
\nStock Purchase Units have been duly executed and delivered in accordance with
\nthe purchase agreement and the applicable definitive purchase, underwriting or
\nsimilar agreement approved by the Board upon payment of the consideration
\ntherefor provided for therein, the Stock Purchase Units will constitute valid
\nand binding obligations of the Company, enforceable against the Company in
\naccordance with their terms (subject to applicable bankruptcy, insolvency,
\nreorganization, fraudulent conveyance, moratorium or other similar laws
\naffecting creditors’ rights generally from time to time in effect and subject to
\ngeneral principles of equity, including concepts of materiality, reasonableness,
\ngood faith and fair dealing, regardless of whether such enforceability is
\nconsidered in a proceeding in equity or at law).<\/p>\n
\n
\nSecurities that (a) relates to the subject matter jurisdiction of any Federal
\ncourt of the United States of America, or any Federal appellate court, to
\nadjudicate any controversy related thereto, (b) contains a waiver of an
\ninconvenient forum, (c) relates to the waiver of rights to jury trial or (d)
\nprovides for indemnification, contribution or limitations on liability. We also
\nexpress no opinion as to (i) the enforceability of the provisions of the
\nIndenture or the Debt Securities to the extent that such provisions constitute a
\nwaiver of illegality as a defense to performance of contract obligations or any
\nother defense to performance which cannot, as a matter of law, be effectively
\nwaived or (ii) whether a state court outside the State of New York or a Federal
\ncourt of the United States would give effect to the choice of New York law
\nprovided for therein.<\/p>\n
\ndamages denominated in any currency other than United States dollars. Section
\n27(b) of the Judiciary Law of the State of New York provides, however, that a
\njudgment or decree in an action based upon an obligation denominated in a
\ncurrency other than United States dollars shall be rendered in the foreign
\ncurrency of the underlying obligation and converted into United States dollars
\nat the rate of exchange prevailing on the date of the entry of the judgment or
\ndecree. We express no opinion as to whether a Federal court would render a
\njudgment other than in United States dollars.<\/p>\n
\nopinion as to matters governed by any laws other than the laws of the State of
\nNew York and the Federal laws of the United States of America. Our opinions set
\nforth above, insofar as they involve matters of the laws of the State of
\nWisconsin, are qualified to the extent that we have relied upon the opinion
\ndated the date hereof of Jake C. Blavat, Senior Attorney of the Company (the
\n“Company Opinion”), and we have assumed, without independent investigation, the
\ncorrectness of, and take no responsibility for, the Company Opinion.<\/p>\n
\nprospectus forming a part of the Registration Statement and that we may be
\nreferred to under a similar heading in a prospectus supplement filed after the
\neffective date of the Registration Statement. We hereby consent to such use of
\nour name therein and the filing of this opinion as Exhibit 5 to the Registration
\nStatement. In giving this consent, we do not hereby admit that we are within the
\ncategory of persons whose consent is required under Section 7 of the Securities
\nAct or the Rules and Regulations of the Commission promulgated thereunder.<\/p>\n\n\n
\n <\/td>\n<\/tr>\n \n \n