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                                                                    Exhibit 32.1

                            CERTIFICATION PURSUANT TO
                             18 U.S.C. SECTION 1350,
                             AS ADOPTED PURSUANT TO
                  SECTION 906 OF THE SARBANES-OXLEY ACT OF 2002

      In connection with the Annual Report of Calpine Corporation (the
"Company") on Form 10-K for the period ending December 31, 2004, as filed with
the Securities and Exchange Commission on the date hereof (the "Report"), each
of the undersigned does hereby certify, pursuant to 18 U.S.C. Section 1350, as
adopted pursuant to Section 906 of the Sarbanes-Oxley Act of 2002, that, to the
best of his knowledge, based upon a review of the Report:

      (1)   The Report fully complies with the requirements of Section 13(a) or
15(d) of the Securities Exchange Act of 1934; and

      (2)   The information contained in the Report fairly presents, in all
material respects, the financial condition and results of operation of the
Company.

/s/ Peter Cartwright                       /s/ Robert D. Kelly
-------------------------------------      -------------------------------------
Peter Cartwright                           Robert D. Kelly
Chairman, President and                    Executive Vice President and
Chief Executive Officer                    Chief Financial Officer
Calpine Corporation                        Calpine Corporation

Dated:  March 31, 2005

A signed original of this written statement required by Section 906 has been
provided to Calpine Corporation and will be retained by Calpine Corporation and
furnished to the Securities and Exchange Commission or its staff upon request.
