INTERSTATE POWER AND LIGHT COMPANY (an Iowa corporation) 3.25% SENIOR DEBENTURES DUE 2024 UNDERWRITING AGREEMENT Dated: November 9, 2017Interstate Power and Light Company • November 15th, 2017 • Alliant Energy Corp • Electric & other services combined • New York
Interstate Power and Light Company, an Iowa corporation (the “Company”), confirms its agreement (the “Agreement”) with BNY Mellon Capital Markets, LLC (“BNY Mellon Capital Markets”), Mizuho Securities USA LLC (“Mizuho”) and Wells Fargo Securities, LLC (“Wells Fargo”), and each of the other underwriters named on Schedule A hereto (collectively, the “Underwriters”, which term shall also include any underwriter substituted as hereinafter provided in Section 10 hereof), for whom BNY Mellon Capital Markets, Mizuho and Wells Fargo are acting as representatives (in such capacity, the “Representatives”), with respect to the issue and sale by the Company and the purchase by the Underwriters, acting severally and not jointly, of the respective principal amounts set forth on Schedule A of $250,000,000 aggregate principal amount of the Company’s 3.25% Senior Debentures due 2024 (the “Securities”) in a reopening of the existing series of previously issued and outstanding 3.25% Senior Debentures due
