FWP

* A securities rating is not a recommendation to buy, sell or hold securities and may be subject to revision or withdrawal at any time.

It is expected that delivery of the Senior Debentures will be made against payment therefor on or about November 19, 2021, which will be the third business day following the date of pricing of the Senior Debentures. Under Rule 15c6-1 of the Securities Exchange Act of 1934, trades in the secondary market generally are required to settle in two business days, unless the parties to any such trade expressly agree otherwise. Accordingly, by virtue of the fact that the Senior Debentures initially will settle in T+3, purchasers who wish to trade the Senior Debentures on any date prior to the second business day before delivery should specify an extended settlement cycle at the time they enter into any such trade to prevent failed settlement and should consult their own advisors.

The issuer has filed a registration statement (including a prospectus) with the Securities & Exchange Commission (the “SEC”) for the offering to which this communication relates. Before you invest, you should read the prospectus in that registration statement and other documents that the issuer has filed with the SEC for more complete information about the issuer and this offering. You may get these documents for free by visiting EDGAR on the SEC Web site at www.sec.gov. Alternatively, you may request a copy of these documents by calling Goldman Sachs & Co. LLC toll free at 1-866-471-2526, J.P. Morgan Securities LLC collect at 1-212-834-4533, MUFG Securities Americas Inc. toll free at 1-877-649-6848 or U.S. Bancorp Investments, Inc. toll free at 1-877-558-2607.

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Issuer:		Interstate Power and Light Company (the “Company”)

Security Type:		Senior Debentures

Principal Amount:		$300,000,000

Maturity Date:		November 30, 2051

Coupon:		3.100%

Price to Public:		99.573% of the principal amount

Yield to Maturity:		3.122%

Benchmark Treasury:		2.000% due August 15, 2051

Benchmark Treasury Yield:		2.022%

Spread to Benchmark Treasury:		+110 bps

Interest Payment Dates:		May 30 and November 30, commencing May 30, 2022

Optional Redemption – Reinvestment Rate:		Prior to May 30, 2051, make-whole call at T+20 bps

Optional Redemption at Par:		On or after May 30, 2051

Trade Date:		November 16, 2021

Settlement Date:		November 19, 2021 (T+3)

CUSIP:		461070 AT1

ISIN:		US461070AT14

Denominations / Multiples:		$2,000 x $1,000

Anticipated Ratings*:		Baa1 / A- (Moody’s/ S&P)

Joint Book-Running Managers:		Goldman Sachs & Co. LLC J.P. Morgan Securities LLC MUFG Securities Americas Inc. U.S. Bancorp Investments, Inc.

Co-Managers:		KeyBanc Capital Markets Inc. Mizuho Securities USA LLC Samuel A. Ramirez & Company, Inc.

		TD Securities (USA) LLC