<SUBMISSION>
<ACCESSION-NUMBER>0000916457-05-000043
<TYPE>NT 10-Q
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<FILING-DATE>20050511
<DATE-OF-FILING-DATE-CHANGE>20050510
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<FILER>
<COMPANY-DATA>
<CONFORMED-NAME>CALPINE CORP
<CIK>0000916457
<ASSIGNED-SIC>4911
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<STATE-OF-INCORPORATION>DE
<FISCAL-YEAR-END>1231
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<BUSINESS-ADDRESS>
<STREET1>50 WEST SAN FERNANDO ST
<CITY>SAN JOSE
<STATE>CA
<ZIP>95113
<PHONE>4089955115
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<STREET1>50 W SAN FERNANDO
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<SEQUENCE>1
<FILENAME>q12005.txt
<TEXT>
                                  UNITED STATES                  SEC File Number
                       SECURITIES AND EXCHANGE COMMISSION           1-12079
                             Washington, D.C. 20549                 -------
                                                                  Cusip Number
                                   FORM 12b-25

                           NOTIFICATION OF LATE FILING



 (Check One) [ ]Form 10-K [ ]Form 20-F [ ]Form 11-K [x]Form 10-Q [ ]Form 10-D
 [ ]Form N-SAR [ ]Form N-CSR

                        For Period Ended: March 31, 2005
                         -------------------------------


                       [ ] Transition Report on Form 10-K
                       [ ] Transition Report on Form 20-F
                       [ ] Transition Report on Form 11-K
                       [ ] Transition Report on Form 10-Q
                       [ ] Transition Report on Form N-SAR
                        For the Transition Period Ended:

  READ INSTRUCTION (ON BACK PAGE) BEFORE PREPARING FORM. PLEASE PRINT OR TYPE.

     Nothing in this form shall be construed to imply that the Commission has
                   verified any information contained herein.

If the notification  relates to a portion of the filing checked above,  identify
the Item(s) to which the notification relates:

                         PART I - REGISTRANT INFORMATION

Calpine Corporation
Full Name of Registrant

Former Name if Applicable

50 West San Fernando Street
Address of Principal Executive Office (STREET AND NUMBER)

San Jose, CA 95113
City, State and Zip Code

                        PART II - RULES 12b-25(b) and (c)

If the subject report could not be filed without  unreasonable effort or expense
and the registrant seeks relief pursuant to Rule 12b-25(b), the following should
be completed. (Check box if appropriate)

[x] (a) The  reason  described  in  reasonable  detail  in Part III of this form
could not be eliminated without unreasonable effort or expense;

[x] (b) The subject annual report, semi-annual report, transition report on Form
10-K, Form 20-F, Form 11-K, Form N-SAR or Form N-CSR, or portion  thereof,  will
be filed on or before the fifteenth  calendar day following the  prescribed  due
date;  or the  subject  quarterly  report or  transition  report on Form 10-Q or
subject  distribution report on Form 10-D, or portion thereof,  will be filed on
or before the fifth calendar day following the prescribed due date; and

[ ] (c) The  accountant's  statement or other exhibit required by Rule 12b-25(c)
has been attached if applicable.

                              PART III - NARRATIVE

State below in reasonable  detail why Forms 10-K, 20-F, 11-K, 10-Q, 10-D, N-SAR,
N-CSR, or the transition  report or portion  thereof,  could not be filed within
the prescribed time period. (Attach Extra Sheets if Needed)

Calpine Corporation was unable to file, without unreasonable effort and expense,
its Quarterly Report on Form 10-Q for the period ended March 31, 2005 (the "Form
10-Q") within the  prescribed  time period  because the registrant was unable to
complete its analysis and preparation of certain financial information contained
in the unaudited financial statements and related footnotes and elsewhere in the
Form  10-Q in time to fully  reflect  such  information  in the Form 10-Q and to
complete its review of the unaudited  financial  statements.  It is  anticipated
that the  Form  10-Q  Quarterly  Report,  along  with  the  unaudited  financial
statements,  will be filed on or  before  the 5th  calendar  day  following  the
prescribed due date of the Registrant's Form 10-Q.



                           PART IV - OTHER INFORMATION



     (1)  Name and  telephone  number  of person  to  contact  in regard to this
          notification

               Lisa Bodensteiner             408             995-5115
          ---------------------------    -----------    ------------------
                     (Name)              (Area Code)    (Telephone Number)



(2) Have all other  periodic  reports  required under Section 13 or 15(d) of the
Securities  Exchange Act of 1934 or Section 30 of the Investment  Company Act of
1940  during  the  preceding  12  months  or for such  shorter  period  that the
registrant  was  required to file such  report(s)  been filed?  If answer is no,
identify report(s). [x] Yes [ ] No

(3) Is it anticipated that any significant  change in results of operations from
the  corresponding  period for the last  fiscal  year will be  reflected  by the
earnings statements to be included in the subject report or portion thereof?
[x] Yes  [ ] No

If so, attach an explanation of the  anticipated  change,  both  narratively and
quantitatively, and, if appropriate, state the reasons why a reasonable estimate
of the results cannot be made.

                               Calpine Corporation
                               -------------------
                  (Name of Registrant as Specified in Charter)

has  caused  this  notification  to be signed on its  behalf by the  undersigned
hereunto duly authorized.





   Date  May 10, 2005                   By  /s/ Charles B. Clark, Jr.
         -------------------------          ----------------------------
                                            Senior Vice President and Controller
                                            Chief Accounting Officer


INSTRUCTION: The form may be signed by an executive officer of the registrant or
by any other duly  authorized  representative.  The name and title of the person
signing  the form  shall  be typed or  printed  beneath  the  signature.  If the
statement is signed on behalf of the registrant by an authorized  representative
(other than an executive officer), evidence of the representative's authority to
sign on behalf of the registrant shall be filed with the form.

                                    ATTENTION
Intentional  misstatements  or omissions  of fact  constitute  Federal  Criminal
Violations (See 18 U.S.C. 1001).

                               GENERAL INSTRUCTIONS

1. This form is required by Rule 12b-25 (17 CFR 240.12b-25) of the General Rules
and Regulations under the Securities Exchange Act of 1934.

2. One signed  original and four  conformed  copies of this form and  amendments
thereto must be completed and filed with the Securities and Exchange Commission,
Washington,  D.C.  20549 in  accordance  with Rule 0-3 of the General  Rules and
Regulations  under the Act. The information  contained in or filed with the form
will be made a matter of public record in the Commission files.

3. A manually signed copy of the form and amendments thereto shall be filed with
each  national  securities  exchange  on which  any class of  securities  of the
registrant is registered.

4.  Amendments to the  notifications  must also be filed on Form 12b-25 but need
not restate  information  that has been correctly  furnished.  The form shall be
clearly identified as an amendment notification.

5. ELECTRONIC FILERS. This form shall not be used by electronic filers unable to
timely file a report  solely due to  electronic  difficulties.  Filers unable to
submit a report  within  the  time  period  prescribed  due to  difficulties  in
electronic  filing  should comply with either Rule 201 or Rule 202 of Regulation
S-T  (Section  232.201  or  Section  232.202  of this  chapter)  or apply for an
adjustment  in filing date  pursuant to Rule 13(b) of  Regulation  S-T  (Section
232.13(b) of this chapter).

                                   ATTACHMENT


Please see our Form 8-K furnished to the Securities  and Exchange  Commission on
May 6, 2005,  for a discussion of the changes in results of operations  from the
corresponding period for the last fiscal year.


                                 End of Filing
</TEXT>
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