UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM 8-K

CURRENT REPORT

Pursuant to Section 13 or 15(d)

of the Securities Exchange Act of 1934

Date of report (Date of earliest event reported): November 5, 2015

Westar Energy, Inc.

(Exact Name of Registrant as Specified in Charter)

Registrant’s telephone number, including area code: (785) 575-6300

Not Applicable

(Former name or former address, if changed from last report)

Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the registrant under any of the following provisions:

Issuance of $550 million of First Mortgage Bonds

On November 13, 2015, we expect to settle the issuance and sale of $250,000,000 in aggregate principal amount of our First Mortgage Bonds, 3.250% Series due 2025 (the “2025 Series Bonds”) and $300,000,000 in aggregate principal amount of our First Mortgage Bonds, 4.250% Series due 2045 (the “2045 Series Bonds” and, together with the 2025 Series Bonds, the “Bonds”), pursuant to an underwriting agreement dated November 5, 2015 with BNY Mellon Capital Markets, LLC, Citigroup Global Markets Inc., Merrill Lynch, Pierce, Fenner & Smith Incorporated and Wells Fargo Securities, LLC as representatives of the several underwriters listed therein, which is filed as Exhibit 1.1 hereto. The 2025 Bonds and the 2045 Bonds will be separate series of securities issued and secured by the Mortgage and Deed of Trust, dated as of July 1, 1939, between us and the Bank of New York Mellon Trust Company, N.A. (as successor to Harris Trust and Savings Bank), as trustee (the “Mortgage”), as amended and supplemented by forty-five indentures supplemental thereto, in addition to the Forty-Second Supplemental (Reopening) Indenture (together, the “Supplemental Indentures” and, together with the Mortgage, the “Amended Mortgage”).

We will pay interest on the Bonds on June 1 and December 1 of each year, beginning on June 1, 2016. Interest on the 2025 Series Bonds accrues from and including November 13, 2015 at a rate of 3.250% per year. Interest on the 2045 Series Bonds accrues from and including November 13, 2015 at a rate of 4.250% per year. The 2025 Series Bonds will mature on December 1, 2025. The 2045 Series Bonds will mature on December 1, 2045. Prior to the applicable Par Call Date (as defined below), we may redeem the Bonds, in whole at any time, or in part from time to time, at a redemption price equal to the greater of: (a) 100% of the principal amount of the Bonds to be redeemed, plus accrued and unpaid interest on those Bonds to but excluding the redemption date, or (b) as determined by the quotation agent, the sum of the present values of the remaining scheduled payments of principal and interest on the Bonds to be redeemed that would be due if the bonds matured on the applicable Par Call Date (not including any portion of payments of interest accrued as of the redemption date) discounted to the redemption date on a semi-annual basis at the adjusted treasury rate plus 15 basis points, in the case of the 2025 Series Bonds, and 20 basis points, in the case of the 2045 Series Bonds, plus accrued and unpaid interest on those Bonds to but excluding the redemption date. On or after the applicable Par Call Date, we may redeem the Bonds at any time in whole, or from time to time in part, at our option, at a redemption price equal to 100% of the principal amount redeemed, plus accrued and unpaid interest on those Bonds to but excluding the redemption date. “Par Call Date” means, in the case of the 2025 Series Bonds, September 1, 2025 and, in the case of the 2045 Series Bonds, June 1, 2045. The Bonds will be secured equally with all other bonds outstanding or hereafter issued under the Mortgage. The Bonds will be issued in minimum denominations of $2,000 and in integral multiples of $1,000 in excess thereof.

The Bonds are being offered pursuant to a registration statement on Form S-3 (File No. 333-187398) previously filed with the Securities and Exchange Commission on March 20, 2013. The foregoing description of the Bonds and the Amended Mortgage is qualified by reference to the full text of the Amended Mortgage, which is filed as Exhibit 4(a) and Exhibit 4(b) to our Registration Statement No. 33-21739, Exhibit 4(o), Exhibit 4(p) and Exhibit 4(q) to our Annual Report on Form 10-K for the year ended December 1, 1992, Exhibit 4(r) to our Registration Statement No. 33-50069, Exhibit 4(s) to our Annual Report on Form 10-K for the year ended December 31, 1994, Exhibit 4(v) to our Annual Report on Form 10-K for the year ended December 31, 2000, Exhibit 4.1 to our Quarterly Report on Form 10-Q for the period ended March 31, 2002, Exhibits 4.1, 4.2 and 4.3 to our Current Report on Form 8-K filed on January 18, 2005, Exhibit 4.1 to our Current Report on Form 8-K filed on June 30, 2005, Exhibit 4.1 to our Current Report on Form 8-K filed on November 24, 2008, Exhibit 4.1 to our Current Report on Form 8-K filed on February 28, 2012, Exhibit 4.1 to our Current Report on Form 8-K filed on May 16, 2012, Exhibit 4.1 to our Current Report on Form 8-K filed on March 22, 2013, Exhibit 4.1 to our Current Report on Form 8-K filed on August 12, 2013 and Exhibit 4.1 hereto, all of which are incorporated by reference herein.

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(d) Exhibits.

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SIGNATURES

Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned hereunto duly authorized.

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INDEX TO EXHIBITS

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