Duke Energy : 424B5

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Table of Contents

Filed Pursuant to Rule 424(b)(5)

Registration Statement No. 333-213765-02

The information in this preliminary prospectus supplement and the accompanying prospectus is not complete and may be changed. This preliminary prospectus supplement and the accompanying prospectus are not an offer to sell these securities, and are not soliciting an offer to buy these securities, in any jurisdiction where the offer and sale is not permitted.

Subject to Completion

Preliminary Prospectus Supplement dated January 3, 2019

PROSPECTUS SUPPLEMENT

(To Prospectus dated January 26, 2017)

$

aggregate principal amount of First Mortgage Bonds in two series. We are offering $ aggregate principal amount of First Mortgage Bonds, % Series, Due February 1, 2029 (the "2029 Mortgage Bonds") and $ aggregate principal amount of First Mortgage Bonds, % Series, Due February 1, 2049 (the "2049 Mortgage Bonds" and, together with the 2029 Mortgage Bonds, the "Mortgage Bonds"). The per annum interest rate on the 2029 Mortgage Bonds will be %. The per annum interest rate on the 2049 Mortgage Bonds will be %.

$	First Mortgage Bonds,	% Series, Due February 1, 2029
$	First Mortgage Bonds,	% Series, Due February 1, 2049
Duke Energy Ohio, Inc. is offering $

We will pay interest on the Mortgage Bonds semi-annually in arrears on February 1 and August 1 of each year, beginning on August 1, 2019. The 2029 Mortgage Bonds will mature as to principal on February 1, 2029. The 2049 Mortgage Bonds will mature as to principal on February 1, 2049. The Mortgage Bonds will be secured by a first mortgage lien, subject only to permitted liens, on substantially all of our tangible electric and natural gas transmission, storage and distribution utility property located in Ohio, together with our recorded easements and rights of way, franchises, licenses, permits, grants, immunities, privileges and rights that are used or useful in the operation of such property, other than Excepted Property (as defined herein).

We may redeem the Mortgage Bonds of either series at our option at any time and from time to time, in whole or in part, as described in this prospectus supplement under the caption "Description of the Mortgage Bonds-Optional Redemption." There will not be any sinking fund for the Mortgage Bonds.

Each series of the Mortgage Bonds is a new issue of securities with no established trading market. We do not intend to list the Mortgage Bonds on any securities exchange or include them in any automated quotation system. Please read the information provided under the caption "Description of the Mortgage Bonds" in this prospectus supplement and "Description of First Mortgage Bonds" in the accompanying prospectus for a more detailed description of the Mortgage Bonds.

Investing in the Mortgage Bonds involves risks. See "Risk Factors" on page S-8 of this prospectus supplement.

Proceeds to

Duke Energy

Per 2029 Mortgage Bond Total 2029 Mortgage Bonds Per 2049 Mortgage Bond Total 2049 Mortgage Bonds

Price to	Underwriting	Ohio, Inc.
Public(1)	Discount(2)	Before Expenses

%

$

% $

$ $

% %

$ $

% %

• (1) Plus accrued interest from January

  , 2019, if settlement occurs after that date.

• (2) The underwriters have agreed to make a payment to us in an amount equal to $ in connection with the offerings. See "Underwriting (Conflicts of Interest)."

, including in respect of expenses incurred by usNeither the Securities and Exchange Commission nor any state securities commission has approved or disapproved of these securities or passed upon the adequacy or accuracy of this prospectus supplement or the accompanying prospectus. Any representation to the contrary is a criminal offense.

We expect the Mortgage Bonds to be ready for delivery only in book-entry form through the facilities of The Depository Trust Company for the accounts of its participants, including Clearstream Banking, S.A. and Euroclear Bank S.A./N.V., on or about January , 2019.

Joint Book-Running Managers

Citigroup

Credit Suisse

Goldman Sachs & Co. LLC

US Bancorp

The date of this prospectus supplement is January

, 2019.

You should rely only on the information contained in or incorporated by reference in this prospectus supplement, the accompanying prospectus and any free writing prospectus authorized by us. We have not, and the underwriters have not, authorized anyone to provide you with information that is different. If anyone provides you with different or inconsistent information, you should not rely on it. We are not, and the underwriters are not, making an offer to sell these securities in any jurisdiction where the offer is not permitted. You should not assume that the information contained in or incorporated by reference in this prospectus supplement, the accompanying prospectus or any free writing prospectus authorized by us is accurate as of any date other than the date of the document containing the information or such other date as may be specified therein. Our business, financial condition, liquidity, results of operations and prospects may have changed since those respective dates.

TABLE OF CONTENTS

Prospectus Supplement

Page

About this Prospectus Supplement S-1

Prospectus Supplement Summary S-3

Risk Factors S-8

Cautionary Statement Regarding Forward-Looking Information S-8

Use of Proceeds S-10

Description of the Mortgage Bonds S-11

Certain U.S. Federal Income Tax Considerations for Non-U.S. Holders S-18

Book-Entry System S-21

Underwriting (Conflicts of Interest) S-25

Legal Matters S-30

Where You Can Find More Information S-30

Prospectus

References to Additional Information

About this Prospectus

Forward-looking Statements

The Company

Risk Factors

Use of Proceeds

Ratio of Earnings to Fixed Charges

Description of First Mortgage Bonds

Description of Unsecured Debt Securities

Global Securities

Plan of Distribution

Experts

Validity of the Securities

Where You Can Find More Information

i i ii 1 1 1 2 2 15 21 22 23 23 23

i

ABOUT THIS PROSPECTUS SUPPLEMENT

This document is in two parts. The first part is this prospectus supplement, which describes the specific terms of these offerings. The second part, the accompanying prospectus, gives more general information, some of which does not apply to these offerings.

If the description of the offerings varies between this prospectus supplement and the accompanying prospectus, you should rely on the information contained in or incorporated by reference in this prospectus supplement.

It is important for you to read and consider all information contained in or incorporated by reference in this prospectus supplement and the accompanying prospectus in making your investment decision. You should also read and consider the information contained in the documents to which we have referred you in "Where You Can Find More Information" in this prospectus supplement and the accompanying prospectus.

Unless we have indicated otherwise, or the context otherwise requires, references in this prospectus supplement and the accompanying prospectus to "Duke Energy Ohio," "the Company," "we," "us" and "our" or similar terms are to Duke Energy Ohio, Inc.

Notice to Prospective Investors in the European Economic Area

Neither this prospectus supplement nor the accompanying prospectus and any related free writing prospectus is a prospectus for the purposes of the Prospectus Directive (as defined below). This prospectus supplement, the accompanying prospectus and any related free writing prospectus have been prepared on the basis that any offer of the Mortgage Bonds in any Member State of the European Economic Area (the "EEA") which has implemented the Prospectus Directive (each, a "Relevant Member State") will only be made to a legal entity which is a qualified investor under the Prospectus Directive ("Qualified Investors"). Accordingly, any person making or intending to make an offer in that Relevant Member State of Mortgage Bonds which are the subject of the offering contemplated in this prospectus supplement, the accompanying prospectus and any related free writing prospectus may only do so with respect to Qualified Investors. Neither Duke Energy Ohio nor the underwriters have authorized, nor do they authorize, the making of any offer of Mortgage Bonds other than to Qualified Investors. The expression "Prospectus Directive" means Directive 2003/71/EC (as amended or superseded), and includes any relevant implementing measure in the Relevant Member State.

Prohibition of Sales to EEA Retail Investors-The Mortgage Bonds are not intended to be offered, sold or otherwise made available to and should not be offered, sold or otherwise made available to any retail investor in the EEA. For these purposes, a retail investor means a person who is one (or more) of: (i) a retail client as defined in point (11) of Article 4(1) of Directive 2014/65/EU, as amended ("MiFID II"); or (ii) a customer within the meaning of Directive (EU) 2016/97, as amended or superseded (the "Insurance Distribution Directive"), where that customer would not qualify as a professional client as defined in point (10) of Article 4(1) of MiFID II; or (iii) not a qualified investor as defined in the Prospectus Directive. Consequently no key information document required by Regulation (EU) No 1286/2014, as amended (the "PRIIPs Regulation") for offering or selling the Mortgage Bonds or otherwise making them available to retail investors in the EEA has been prepared and therefore offering or selling the Mortgage Bonds or otherwise making them available to any retail investor in the EEA may be unlawful under the PRIIPs Regulation.

Notice to Prospective Investors in the United Kingdom

The communication of this prospectus supplement, the accompanying prospectus, any related free writing prospectus and any other document or materials relating to the issue of the Mortgage Bonds offered hereby is not being made, and such documents and/or materials have not been approved, by an

S-1