<PAGE>   1


     AS FILED WITH THE SECURITIES AND EXCHANGE COMMISSION ON JULY 30, 2001


                                                      REGISTRATION NO. 333-59786

--------------------------------------------------------------------------------
--------------------------------------------------------------------------------

                       SECURITIES AND EXCHANGE COMMISSION
                             WASHINGTON, D.C. 20549
                           -------------------------


                                AMENDMENT NO. 1


                                       TO


                                    FORM S-3
                             REGISTRATION STATEMENT
                                     UNDER
                           THE SECURITIES ACT OF 1933
                           -------------------------

                              CALPINE CORPORATION
             (EXACT NAME OF REGISTRANT AS SPECIFIED IN ITS CHARTER)

<Table>
<S>                              <C>                              <C>
           DELAWARE                           4911
77-0212977
(STATES OR OTHER JURISDICTIONS    (PRIMARY STANDARD INDUSTRIAL           (I.R.S.
EMPLOYER
              OF                  CLASSIFICATION CODE NUMBERS)
IDENTIFICATION NUMBERS)
INCORPORATION OR ORGANIZATION)
</Table>

                          50 WEST SAN FERNANDO STREET
                           SAN JOSE, CALIFORNIA 95113
                                 (408) 995-5115
  (ADDRESS, INCLUDING ZIP CODE, AND TELEPHONE NUMBER, INCLUDING AREA CODE, OF
                   REGISTRANT'S PRINCIPAL EXECUTIVE OFFICES)

                                PETER CARTWRIGHT
      CHAIRMAN, PRESIDENT AND CHIEF EXECUTIVE OFFICER, CALPINE CORPORATION
                          50 WEST SAN FERNANDO STREET
                           SAN JOSE, CALIFORNIA 95113
                                 (408) 995-5115
 (NAME, ADDRESS, INCLUDING ZIP CODE, AND TELEPHONE NUMBER, INCLUDING AREA CODE,
                             OF AGENT FOR SERVICE)

                                   COPIES TO:
                                BRUCE C. BENNETT
                              COVINGTON & BURLING
                          1330 AVENUE OF THE AMERICAS
                            NEW YORK, NEW YORK 10019
                                 (212) 841-1000

        APPROXIMATE DATE OF COMMENCEMENT OF PROPOSED SALE TO THE PUBLIC:
   From time to time after the effective date of this Registration Statement.

     If the only securities being registered on this Form are being offered
pursuant to dividend or interest reinvestment plans, please check the following
box:  [ ]

     If any of the securities being registered on this Form are to be offered on
a delayed or continuous basis pursuant to Rule 415 under the Securities Act of
1933, other than securities offered only in connection with dividend or interest
reinvestment plans, please check the following box:  [X]

     If this Form is filed to register additional securities for an offering
pursuant to Rule 462(b) under the Securities Act, please check the following box
and list the Securities Act registration statement number of the earlier
effective registration statement for the same offering:  [ ] __________

     If this Form is a post-effective amendment filed pursuant to Rule 462(c)
under the Securities Act, check the following box and list the Securities Act
registration statement number of the earlier effective registration statement
for the same offering:  [ ] __________

     If delivery of the prospectus is expected to be made pursuant to Rule 434,
please check the following box:  [ ]


     THE REGISTRANT HEREBY AMENDS THIS REGISTRATION STATEMENT ON SUCH DATE OR
DATES AS MAY BE NECESSARY TO DELAY ITS EFFECTIVE DATE UNTIL THE REGISTRANT SHALL
FILE A FURTHER AMENDMENT WHICH SPECIFICALLY STATES THAT THIS REGISTRATION
STATEMENT SHALL THEREAFTER BECOME EFFECTIVE IN ACCORDANCE WITH SECTION 8(a) OF
THE SECURITIES ACT OF 1933 OR UNTIL THIS REGISTRATION STATEMENT SHALL BECOME
EFFECTIVE ON SUCH DATE AS THE COMMISSION, ACTING PURSUANT TO SAID SECTION 8(a),
MAY DETERMINE.


--------------------------------------------------------------------------------
--------------------------------------------------------------------------------
<PAGE>   2

THE INFORMATION IN THIS PROSPECTUS IS NOT COMPLETE AND MAY BE CHANGED. WE MAY
NOT SELL THESE SECURITIES UNTIL THE REGISTRATION STATEMENT FILED WITH THE
SECURITIES AND EXCHANGE COMMISSION RELATING TO THESE SECURITIES IS EFFECTIVE.
THIS PROSPECTUS IS NOT AN OFFER TO SELL THESE SECURITIES AND IS NOT SEEKING AN
OFFER TO BUY THESE SECURITIES IN ANY STATE WHERE THE OFFER OR SALE IS NOT
PERMITTED.


                   SUBJECT TO COMPLETION, DATED JULY 30, 2001


PROSPECTUS

                                 151,176 Shares

                              CALPINE CORPORATION

                                  Common Stock
                          (Par Value $.001 per share)

     This prospectus relates to the resales of shares of common stock of Calpine
Corporation, a Delaware corporation, by the selling holders named in this
prospectus. The shares have been issued to the former shareholders of WRMS
Engineering, Inc., a California corporation, in connection with our acquisition
of WRMS. We will not receive any cash proceeds from this offering.


     Up to 151,176 shares of the common stock offered hereby may be resold by
the selling holders named in this prospectus. The selling holders will receive
all of the proceeds from the sale of the securities and will pay any
underwriting discounts and selling commissions applicable to any sale. The
selling holders and any broker-dealers, agents or underwriters that participate
in the distribution of the securities may be deemed to be "underwriters" within
the meaning of the Securities Act, and any commission received by them and any
profit on the resale of the securities purchased by them may be deemed to be
underwriting commission or discounts under the Securities Act.


     We are paying all expenses of registration incurred in connection with this
offering, other than underwriter commissions and similar selling fees and
transfer costs.


     Calpine's common stock is traded on The New York Stock Exchange under the
symbol "CPN." On July 27, 2001, the last reported sales price of the common
stock on that exchange was $37.90. Unless otherwise indicated, all dollar
references in this prospectus are to U.S. dollars.



     INVESTING IN CALPINE'S COMMON STOCK INVOLVES RISKS. SEE "RISK FACTORS" ON
PAGE 9.


     NEITHER 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. ANY REPRESENTATION TO THE CONTRARY IS A
CRIMINAL OFFENSE.


             The date of this prospectus is                , 2001.

<PAGE>   3

                               TABLE OF CONTENTS


<Table>
<Caption>
                                                              PAGE
                                                              ----
<S>                                                           <C>
The Company.................................................    1
Risk Factors................................................    9
Where You Can Find More Information.........................    9
Forward-Looking Statements..................................   10
Use of Proceeds.............................................   11
Selling Holders.............................................   11
Plan of Distribution........................................   12
Description of Our Capital Stock............................   12
Certain United States Federal Income Tax Consequences.......   16
Legal Matters...............................................   18
Independent Public Accountants..............................   19
</Table>


                           -------------------------

     This document is called a prospectus and is part of a registration
statement that we filed with the Securities and Exchange Commission (the "SEC")
using a "shelf" registration or continuous offering process.

     The registration statement containing this prospectus, including the
exhibits to the registration statement, provides additional information about us
and the securities offered under this prospectus. The registration statement,
including the exhibits, can be read at the SEC web site or at the SEC offices
mentioned under the heading "Where You Can Find More Information."

     You should rely only on the information incorporated by reference or
provided in this prospectus. We have not authorized anyone to provide you with
different information. We are not making an offer or soliciting a purchase of
these securities in any jurisdiction in which the offer or solicitation is not
authorized or in which the person making the offer or solicitation is not
qualified to do so or to anyone to whom it is unlawful to make the offer or
solicitation. You should not assume that the information in this prospectus or
the prospectus supplement is accurate as of any date other than the date on the
front of the document.

     The prospectus incorporates business and financial information about us
that is not included in or delivered with the document. YOU MAY REQUEST AND
OBTAIN THIS INFORMATION FREE OF CHARGE BY WRITING OR TELEPHONING US AT THE
FOLLOWING ADDRESS: CALPINE CORPORATION, 50 WEST SAN FERNANDO STREET, SAN JOSE,
CALIFORNIA 95113, ATTENTION: LISA M. BODENSTEINER, ASSISTANT SECRETARY,
TELEPHONE: (408) 995-5115.

     Unless we have indicated otherwise, references in this prospectus to
"Calpine," "we," "us," and "our" or similar terms are to Calpine Corporation and
its consolidated subsidiaries.

                                        i
<PAGE>   4


                                  THE COMPANY



     We are a leading independent power company engaged in the development,
acquisition, ownership and operation of power generation facilities and the sale
of electricity predominantly in the United States. We have experienced
significant growth in all aspects of our business over the last five years.
Currently, we own interests in 56 power plants having a net capacity of 8,615
megawatts. We also have 25 gas-fired projects under construction having a net
capacity of 14,092 megawatts and have announced plans to develop 33 gas-fired
projects (power plants and expansions of current facilities) with a net capacity
of 17,750 megawatts. Upon completion of the projects under construction, we will
have interests in 80 power plants located in 23 states and Canada, having a net
capacity of 22,707 megawatts. Of this total generating capacity, 96% will be
attributable to gas-fired facilities and 4% will be attributable to geothermal
facilities. As a result of our expansion program, our revenues, cash flow,
earnings and assets have grown significantly over the last five years, as shown
in the table below. Except as otherwise noted herein, financial information in
this prospectus does not reflect any impact on our financial position or results
of operations that will result from our business combination under the pooling
of interests method of accounting consummated on April 19, 2001 with Encal
Energy Ltd.



<Table>
<Caption>

COMPOUND ANNUAL
                                                   1996        2000
GROWTH RATE
                                                 --------    --------
---------------
                                                    (IN MILLIONS)
<S>                                              <C>         <C>         <C>
Total Revenue..................................  $  214.6    $2,282.8
81%
EBITDA.........................................     110.7       825.9
65%
Net Income.....................................      18.7       323.5
104%
Total Assets...................................   1,031.4     9,737.3
75%
</Table>



     Since our inception in 1984, we have developed substantial expertise in all
aspects of the development, acquisition and operation of power generation
facilities. We believe that the vertical integration of our extensive
engineering, construction management, operations, fuel management and financing
capabilities provides us with a competitive advantage to successfully implement
our acquisition and development program and has contributed to our significant
growth over the past five years.



     We are a corporation organized and existing under the laws of the State of
Delaware. Our principal executive office is located at 50 West San Fernando
Street, San Jose, California 95113. Our registered office is located at 9 East
Loockerman Street, Dover, Delaware 19901, c/o National Registered Agents, Inc.



THE MARKET



     The power industry represents the third largest industry in the United
States, with an estimated end-user market of over $215 billion of electricity
sales in 2000 produced by an aggregate base of power generation facilities with
a capacity of approximately 860,000 megawatts. In response to increasing
customer demand for access to low-cost electricity and enhanced services, new
regulatory initiatives have been and are continuing to be adopted at both the
state and federal level to increase competition in the domestic power generation
industry. The power generation industry historically has been largely
characterized by electric utility monopolies producing electricity from old,
inefficient, high-cost generating facilities selling to a captive customer base.
Industry trends and regulatory initiatives have transformed the existing market
into a more competitive market where end-users purchase electricity from a
variety of suppliers, including non-utility generators, power marketers, public
utilities and others.



     There is a significant need for additional power generating capacity
throughout the United States, both to satisfy increasing demand and to replace
old and inefficient generating facilities. Due to environmental and economic
considerations, we believe this new capacity will be provided predominantly by
gas-fired facilities. We believe that these market trends will create
substantial opportunities for efficient, low-cost power producers that can
produce and sell energy to customers at competitive rates.


                                        1
<PAGE>   5


     In addition, as a result of a variety of factors, including deregulation of
the power generation market, utilities, independent power producers and
industrial companies are disposing of power generation facilities. To date,
numerous utilities have sold or announced their intentions to sell their power
generation facilities and have focused their resources on the transmission and
distribution business segments. Many independent producers operating a limited
number of power plants are also seeking to dispose of their plants in response
to competitive pressures and industrial companies are selling their power plants
to redeploy capital in their core businesses.



STRATEGY



     Our strategy is to continue our rapid growth by capitalizing on the
significant opportunities in the power market, primarily through our active
development and acquisition programs. In pursuing this growth strategy, we
utilize our management and technical knowledge to implement a fully integrated
approach to the acquisition, development and operation of power generation
facilities. This approach uses our expertise in design, engineering,
procurement, finance, construction management, fuel and resource production and
acquisition, operations and power marketing, which we believe provides us with a
competitive advantage. The key elements of our strategy are as follows:



     - Development of new and expansion of existing power plants. We are
      actively pursuing the development of new and expansion of our existing
      highly efficient, low-cost, gas-fired power plants to replace old and
      inefficient generating facilities and meet the demand for new generation.



     - Acquisition of power plants. Our strategy is to acquire power generating
      facilities that meet our stringent criteria, provide significant potential
      for revenue, cash flow and earnings growth and provide the opportunity to
      enhance the operating efficiencies of the plants.



     - Enhancement of existing power plants. We continually seek to maximize the
      power generation and revenue potential of our operating assets and
      minimize our operating and maintenance expenses and fuel costs.



ACQUISITION OF WRMS



     On April 3, 2001, we acquired all of the common shares of WRMS Engineering,
Inc., a Walnut Creek, California-based engineering and architectural firm
specializing in critical use facilities for the commercial, industrial and
governmental sectors, including hospitals, bio-research facilities,
telecommunication and data centers, fossil fuel plants and waste treatment
facilities, through a stock-for-stock exchange in which WRMS shareholders
received a total of 151,176 shares of Calpine common stock. The aggregate value
of the transaction was approximately $7.5 million, excluding the assumed
indebtedness of WRMS. The Registration Statement of which this prospectus is a
part is being filed with the SEC in order to register shares of our common stock
to allow for resales of such common stock by selling holders who are officers of
WRMS.



RECENT DEVELOPMENTS



     In addition to the recent developments described below, please see the
recent developments described in our Annual Report on Form 10-K for the year
ended December 31, 2000, our Quarterly Report on Form 10-Q for the quarter ended
March 31, 2001 and our Current Reports on Form 8-K dated April 19, 2001, June
26, 2001, July 6, 2001, July 12, 2001 and July 26, 2001, which are incorporated
by reference in this prospectus.



     Second Quarter 2001 Earnings. On July 26, 2001, we announced earnings for
the quarter ended June 30, 2001. Net income from recurring operations (before
deduction of nonrecurring merger costs incurred in connection with the Encal
pooling of interests transaction) was $132.2 million for the quarter ended June
30, 2001, representing a 122% increase over 2000 second quarter net income of
$59.5 million. Diluted earnings per share from recurring operations (before
deduction of nonrecurring merger costs of $0.07 per share) for the second
quarter rose 95% to $0.39 per share, from $0.20 per share for the same


                                        2
<PAGE>   6


period last year. Revenue for the quarter increased 284% to $1.6 billion, from
$417 million a year ago. Total assets at June 30, 2001 were approximately $16.0
billion as compared to $10.3 billion at December 31, 2000. As a result of the
completion of the Encal pooling-of-interests transaction, the financial results
for the quarter and six months ended June 30, 2000, and for the quarter ended
March 31, 2001, have been restated to include Encal. Earnings for the quarter
and six months ended June 30, 2001 benefited primarily from the continued
execution of our program to own and operate low-cost generating facilities in
key power markets throughout the United States and Calpine Energy Services'
successful power systems program.



     Acquisitions. On April 19, 2001, we closed the acquisition of all of the
common shares of Encal Energy Ltd. (which was thereafter merged with and into
Calpine Canada Resources Ltd.), a Calgary, Alberta-based natural gas and
petroleum exploration and development company, through a stock-for-stock
exchange in which Encal shareholders received, in exchange for each share of
Encal common stock, .1493 shares of Calpine common equivalent shares (called
"exchangeable shares") of our subsidiary, Calpine Canada Holdings Ltd. A total
of 16,603,633 exchangeable shares were issued to Encal shareholders in exchange
for their Encal common stock. Each exchangeable share is exchangeable for one
share of our common stock. The aggregate value of the transaction was
approximately U.S.$1.1 billion, including the assumed indebtedness of Encal.
With the addition of Encal's assets, which currently produce approximately 230
million cubic feet of gas equivalent ("mmcfe") per day, net of royalties, our
net production increased to 390 mmcfe per day in North America, enough to fuel
approximately 2,300 megawatts of our power fleet.



     On May 15, 2001, we announced that our wholly-owned subsidiary, Canada
Power Holdings Ltd., had entered into a letter of intent to acquire from British
Columbia-based Westcoast Energy, Inc. a 100% interest in Westcoast's 250
megawatt facility located on Vancouver Island and a 50% interest in its 50
megawatt facility located in Ontario for approximately U.S.$255 million. The
acquisition is expected to close in the third quarter of this year and is
subject to final documentation and third party and regulatory approvals.



     On July 5, 2001, we announced an agreement to acquire a 1,200 megawatt
natural gas-fired power plant at Saltend near Hull, Yorkshire, England from
Entergy Wholesale Operations for approximately L560 million (approximately
U.S.$800 million at current exchange rates). The Saltend facility, a
cogeneration facility, provides electricity and steam for BP Chemical's Hull
Works plant under a 15-year agreement. The balance of the Saltend facility's
electricity output is sold into the deregulated UK power market. The Saltend
transaction will be our first acquisition of a power facility in Europe. The
acquisition is expected to close in the third quarter of this year and is
subject to third party approvals.



     On July 10, 2001, we announced an agreement to acquire approximately 85% of
the voting stock of Michael Petroleum Corporation, a Houston, Texas-based
natural gas exploration and development company, for approximately $270 million
and the assumption of $49.5 million of debt. The acquisition includes 204
billion cubic feet equivalent of proven natural gas reserves currently producing
43 mmcfe per day and an inventory of high quality, low risk drilling locations
within a 94,000 acreage position in close proximity to our South Texas Magic
Valley and Hidalgo Energy Centers. The acquisition is expected to close August
15, 2001.



     Turbine Contract. On April 19, 2001, we announced the purchase of 35 model
7FB and 11 model 7FA gas-fired turbines from GE Power Systems. We expect to take
delivery of five turbines in 2002, with the remainder of the contract to be
filled by the end of 2005. With this purchase, we have firm orders in place for
the delivery of 203 turbines which, when operated in a combined-cycle
configuration, will produce approximately 50,000 megawatts of baseload capacity.



     Securities. On April 25, 2001, Calpine Canada Energy Finance ULC ("Energy
Finance"), our indirect wholly-owned subsidiary, issued $1.5 billion in
aggregate principal amount of its 8 1/2% Senior Notes Due 2008. The Senior Notes
Due 2008 are fully and unconditionally guaranteed by us.


                                        3
<PAGE>   7


     On April 30, 2001, we completed the private placement in a Rule 144A
transaction of $1.0 billion in aggregate principal amount of our Zero-Coupon
Convertible Debentures Due April 30, 2021. Each debenture is convertible into
13.2714 shares of our common stock (representing an initial conversion price of
$75.35 per share of common stock). The debentures do not pay interest, except
that interest may become payable in certain circumstances if the trading price
of the debentures falls below a designated level.



     On June 7, 2001, we redeemed all $105 million in aggregate outstanding
principal amount of our 9 1/4% Senior Notes Due 2004 at a redemption price of
100% of the principal amount of the Senior Notes Due 2004, plus accrued interest
to the redemption date.



     California Power Market. The deregulation of the California power market
has produced significant unanticipated results in the past year. The
deregulation froze the rates that utilities can charge their retail and business
customers in California and prohibited the utilities from buying power on a
forward basis, while wholesale power prices were not subjected to limits.



     In the past year and a half, a series of factors have reduced the supply of
power to California, which has resulted in wholesale power prices that have been
significantly higher than historical levels. Several factors contributed to this
increase. These included:


     - significantly increased volatility in prices and supplies of natural gas;

     - an unusually dry fall and winter in the Pacific Northwest, which reduced
       the amount of available hydroelectric power from that region (typically,
       California imports a portion of its power from this source);

     - the large number of power generating facilities in California nearing the
       end of their useful lives, resulting in increased downtime (either for
       repairs or because they have exhausted their air pollution credits and
       replacement credits have become too costly to acquire on the secondary
       market); and

     - continued obstacles to new power plant construction in California, which
       deprived the market of new power sources that could have, in part,
       ameliorated the adverse effects of the foregoing factors.


     As a result of this situation, two major California utilities that are
subject to the retail rate freeze, including Pacific Gas & Electric Company
("PG&E"), have faced wholesale prices that far exceed the retail prices they are
permitted to charge. This has led to significant under-recovery of costs by
these utilities. As a consequence, these utilities have defaulted under a
variety of contractual obligations, including payment obligations to power
generators. PG&E has defaulted on payment obligations to Calpine under Calpine's
long-term qualifying facility ("QF") contracts, which are subject to federal
regulation under the Public Utility Regulatory Policies Act of 1978, as amended
("PURPA"). The PG&E QF contracts are in place at eleven of our facilities and
represent nearly 600 megawatts of electricity for Northern California customers.



     PG&E Bankruptcy Proceedings. On April 6, 2001, PG&E filed for bankruptcy
protection under Chapter 11 of the United States Bankruptcy Code. As of April 6,
2001, we had recorded approximately $266 million in accounts receivable with
PG&E under our QF contracts, plus a $69 million note receivable not yet due and
payable. We are currently selling power to PG&E pursuant to our long-term QF
contracts, and PG&E is paying on a current basis for these purchases since its
bankruptcy filing. With respect to the receivables recorded under these
contracts, on July 6, 2001, Calpine announced that it had entered into a binding
agreement with PG&E to modify all of Calpine's QF contracts with PG&E and that,
based upon such modification, PG&E had agreed to assume all of the QF contracts.
Under the terms of this agreement, Calpine will continue to receive its
contractual capacity payments under the QF contracts, plus a five-year fixed
energy price component of approximately 5.37 cents per kilowatt-hour. In
addition, all past due receivables under the QF contracts will be elevated to
administrative priority status in the PG&E bankruptcy proceeding and will be
paid to Calpine, with interest, upon the effective date of a confirmed plan of
reorganization. Administrative claims enjoy priority over payments made to the
general unsecured


                                        4
<PAGE>   8


creditors in bankruptcy. The Bankruptcy Court approved the agreement on July 12,
2001. We cannot predict when the bankruptcy court will confirm a plan of
reorganization for PG&E.



     CPUC Proceedings Regarding QF Contract Pricing. Our QF contracts with PG&E
provide that the California Public Utilities Commission ("CPUC") has the
authority to determine the appropriate utility "avoided cost" to be used to set
energy payments for certain QF contracts, including those for all of our QF
plants in California which sell power to PG&E. Section 390 of the California
Public Utility Code provides QFs the option to elect to receive energy payments
based on the California Power Exchange ("PX") market clearing price. In
mid-2000, our QF facilities elected this option and were paid based upon the PX
zonal day ahead clearing price ("PX Price") from summer 2000 until January 19,
2001, when the PX ceased operating a day ahead market. Since that time, the CPUC
has ordered that the price to be paid for energy deliveries by QFs electing the
PX Price shall be based on a natural gas cost-based "transition formula." The
CPUC has conducted proceedings (R.99-11-022) to determine whether the PX Price
was the appropriate price for the energy component upon which to base payments
to QFs which had elected the PX based pricing option. The CPUC has issued a
proposed decision to the effect that the PX price was the appropriate price for
energy payments under the California Public Utility Code. However, a final
decision has not been issued to date. Therefore, it is possible that the CPUC
could order a payment adjustment based on a different energy price
determination. We believe that the PX Price was the appropriate price for energy
payments but there can be no assurance that this will be the outcome of the CPUC
proceedings.



     California Long-Term Supply Contracts. California has adopted legislation
permitting it to issue long-term revenue bonds to provide funding for wholesale
purchases of power. The bonds will be repaid with the proceeds of payments by
retail customers over time. The California Department of Water Resources ("DWR")
sought bids for long-term power supply contracts in a publicly announced
auction. Calpine successfully bid in that auction and signed several long-term
power supply contracts with DWR.



     On February 7, 2001, we announced the signing of a 10-year, $4.6 billion
fixed-price contract with DWR to provide electricity to the State of California.
We committed to sell up to 1,000 megawatts of electricity, with initial
deliveries of 200 megawatts starting October 1, 2001, which increases to 1,000
megawatts by January 1, 2004. The electricity will be sold directly to DWR on a
24-hour, 7-day-a-week basis. This contract is contingent upon our satisfaction,
in our sole discretion, that adequate provisions have been made by DWR to assure
us of full payment under the terms of the contract (including the terms and
conditions of any bonds issued by DWR to provide funds for payment of its
obligations under the contract).



     On February 28, 2001, we announced the signing of two long-term power sales
contracts with DWR. Under the terms of the first contract, a 10-year, $5.2
billion fixed-price contract, we committed to sell up to 1,000 megawatts of
generation. Initial deliveries began July 1, 2001 with 200 megawatts and
increase to 1,000 megawatts by as early as July 2002. Under the terms of the
second contract, a 20-year contract totaling up to $3.1 billion, we will supply
DWR with up to 495 megawatts of peaking generation, beginning with 90 megawatts
as early as August 2001, and increasing up to 495 megawatts as early as August
2002. Each of these contracts is also contingent upon our satisfaction, in our
sole discretion, that adequate provisions have been made by DWR to assure us of
full payment under the terms of that contract (including the terms and
conditions of any bonds issued by DWR to provide funds for payment of its
obligations under that contract).



     FERC Investigation into California Wholesale Markets. In response to the
increase in wholesale energy prices in the California markets, on June 28, 2000,
the Board of Governors of the California Independent System Operator (the
"ISO"), which controls the long-distance high-voltage power lines that deliver
electricity throughout California and adjoining states, reduced the price cap
applicable to the ISO's wholesale energy and ancillary services markets from
$750/MWh to $500/MWh. The ISO subsequently reduced the price cap to $250/MWh
effective August 7, 2000. During this period, however, the PX maintained a
separate price cap set at a much higher level applicable to the "day-ahead" and
"day-of" markets administered by the PX. On August 23, 2000, the Federal Energy
Regulatory Commission


                                        5
<PAGE>   9


("FERC") denied a complaint filed August 2, 2000 by San Diego Gas & Electric
Company ("SDG&E") that sought to extend the ISO's $250 price cap to all
California energy and ancillary service markets, not just the markets
administered by the ISO. However, in its order denying the relief sought by
SDG&E, FERC instructed its staff to initiate an investigation of the California
power markets and to report its findings to FERC and held further hearing
procedures in abeyance pending the outcome of this investigation. Under FERC
regulations, QF contracts are exempt from regulation under the Federal Power
Act, which is the legislation that provides the authority for FERC to
investigate the California power markets and frame equitable relief with respect
to the California wholesale markets. Therefore, any such relief will only apply
to sales by Calpine in the short-term market. None of Calpine's receivables
related to power produced under its long-term QF contracts with PG&E should be
affected by any FERC findings pursuant to the proceedings described below. See
"Government Regulation -- Federal Energy Regulation -- Federal Power Act
Regulation" set forth in our Annual Report on Form 10-K for the year ended
December 31, 2000, which is incorporated by reference in this prospectus.



     On November 1, 2000, FERC released a Staff Report detailing the results of
the Staff investigation, together with an "Order Proposing Remedies for
California Wholesale Markets" (the "November 1 Order"). In the November 1 Order,
FERC found that the California power market structure and market rules were
seriously flawed, and that these flaws, together with short supply relative to
demand, resulted in unusually high energy prices. The November 1 Order proposed
specific remedies to the identified market flaws, including: (a) imposition of a
so-called "soft" price cap at $150/MWh to be applied to both the PX and ISO
markets, which would allow bids above $150/MWh to be accepted, but would subject
such bids to certain reporting obligations requiring sellers to provide cost
data and/or identify applicable opportunity costs and specifying that such bids
may not set the overall market clearing price; (b) elimination of the
requirement that the California utilities sell into and buy from the PX; (c)
establishment of independent non-stakeholder governing boards for the ISO and
the PX; and (d) establishment of penalty charges for scheduling deviations
outside of a prescribed range. In the November 1 Order FERC established October
2, 2000, the date 60 days after the filing of the SDG&E complaint, as the
"refund effective date." Under the November 1 Order, rates charged for service
after that date through December 31, 2002 will remain subject to refund if
determined by FERC not to be just and reasonable. While FERC concluded that the
Federal Power Act and prior court decisions interpreting that act strongly
suggested that refunds would not be permissible for charges in the period prior
to October 2, 2000, it noted that it was willing to explore proposals for
equitable relief with respect to charges made in that period.



     On December 15, 2000, FERC issued a subsequent order that affirmed in large
measure the November 1 Order (the "December 15 Order"). Various parties have
filed requests for administrative rehearing and for judicial review of aspects
of FERC's December 15 Order. The outcome of these proceedings, and the extent to
which FERC or a reviewing court may revise aspects of the December 15 Order or
the extent to which these proceedings may result in a refund of or reduction in
the amounts charged by the our subsidiaries for power sold in the ISO and PX
markets, cannot be determined at this time.



     On June 19, 2001, FERC ordered price mitigation in 11 states in the western
United States in an attempt to reduce the dependence of the California market on
spot markets in favor of longer-term committed energy supplies. The order
provides for price mitigation in the spot market throughout the 11 state western
region during "reserve deficiency hours," which is when operating reserves in
California fall below seven percent. This price will be a single market clearing
price based upon the marginal operating cost of the last unit dispatched by the
California ISO. In addition, FERC implemented price mitigation in non-reserve
deficiency hours, which will be set at 85% of the market clearing price during
the last reserve deficiency period. These price mitigation procedures went into
effect on June 20, 2001 and will remain in effect until September 30, 2002.



     The retention by FERC of a market-based, rather than a
cost-of-service-based, rate structure, will enable us to continue to realize
benefits from our efficient, modern power plants. We believe that Calpine's
marginal costs will continue to be below any price cap imposed by FERC, whether
during reserve


                                        6
<PAGE>   10


deficiency hours or at other times. Therefore, we believe that FERC's mitigation
plan will not have a material adverse effect on Calpine's financial condition or
results of operations.



     FERC also ordered all sellers and buyers in wholesale power markets
administered by the California ISO, as well as representatives of the State of
California, to participate in a settlement conference before a FERC
administrative judge. The settlement discussions were intended to resolve all
issues that remain outstanding to resolve past accounts, including sellers'
claims for unpaid invoices, and buyers' claims for refunds of alleged
overcharges, for past periods. The settlement discussions began on June 25, 2001
and ended on July 9, 2001. The Chief Administrative Law Judge issued his report
and recommendations to FERC on July 12, 2001. On July 25, 2001, FERC ordered an
expedited fact-finding hearing to calculate refunds for spot market transactions
in California. The hearing must be completed within 45 days from the date the
California ISO provides certain critical data for the purpose of developing the
factual basis needed to implement the refund methodology and order refunds.
While it is not possible to predict the amount of any refunds until the hearings
take place, based upon the information available at this time, we do not believe
that this proceeding will result in a material adverse effect on Calpine's
financial condition or results of operations.




                                        7
<PAGE>   11


CAPITALIZATION



     The following table sets forth, as of March 31, 2001 (1) our actual
consolidated capitalization; and (2) our consolidated capitalization as adjusted
to reflect the net effect of (a) our acquisition of WRMS, including the issuance
of our common stock in connection therewith, (b) our business combination with
Encal, including the issuance of our common stock upon exchange of the
exchangeable securities offered thereby, (c) the sale of $1.5 billion in
aggregate principal amount of Energy Finance's 8 1/2% Senior Notes Due 2008,
guaranteed by us and the use of proceeds thereof, (d) the sale of $1.0 billion
in aggregate principal amount of our Zero-Coupon Convertible Debentures Due 2021
and the use of proceeds thereof and (e) the redemption of $105 million in
aggregate principal amount of our 9 1/4% Senior Notes Due 2004. The adjustments
do not reflect normal day-to-day operations. This table should be read in
conjunction with the consolidated financial statements and related notes thereto
and the unaudited pro forma combined condensed financial statements and related
notes thereto incorporated by reference in this prospectus.



<Table>
<Caption>
                                                                    MARCH 31,
2001

--------------------------
                                                                ACTUAL      AS
ADJUSTED
                                                              ----------
------------
                                                                     (UNAUDITED)
                                                                    (IN
THOUSANDS,
                                                                EXCEPT SHARE
AMOUNTS)
<S>                                                           <C>           <C>
SHORT-TERM DEBT:
Notes payable and borrowings under lines of credit, current
  portion...................................................  $      851    $
    851
Project financing, current portion..........................      91,571
  1,177
Capital lease obligation, current portion...................       2,050
  2,050
Zero-Coupon Convertible Debentures Due 2021.................          --
1,000,000
                                                              ----------
------------
                                                                  94,472
1,004,078
LONG-TERM DEBT:
Notes payable and borrowings under lines of credit, net of
  current portion...........................................     133,955
  7,713
Project financing, net of current portion...................   1,646,564
841,958
Senior notes................................................   3,701,750
5,096,750
Capital lease obligation, net of current portion............     208,840
209,065
                                                              ----------
------------
          Total long-term debt..............................   5,691,109
6,155,486
                                                              ----------
------------
Company-obligated mandatorily redeemable convertible
  preferred securities of subsidiary trusts.................   1,122,686
1,122,686
Minority interests..........................................      41,180
 41,180
                                                              ----------
------------
STOCKHOLDERS' EQUITY:
Preferred stock, $.001 par value:
  10,000,000 shares authorized; no shares outstanding,
     actual, and one share outstanding, as adjusted.........          --
     --
                                                              ----------
------------
Common stock, $.001 par value:
  1,000,000,000 shares authorized; 285,113,768 shares
     outstanding, actual, and 301,868,577 shares
     outstanding, as adjusted...............................         285
    302
Additional paid-in capital..................................   1,734,202
1,938,183
Retained earnings...........................................     631,394
607,413
Accumulated other comprehensive loss........................     (56,694)
(77,344)
                                                              ----------
------------
          Total stockholders' equity........................   2,309,187
2,468,554
                                                              ----------
------------
          Total capitalization..............................  $9,258,634    $
10,791,984
                                                              ==========
============
</Table>


                                        8
<PAGE>   12

                                  RISK FACTORS


     Investing in our common stock involves risk. In addition to the risk
factors described in our Annual Report on Form 10-K for the year ended December
31, 2000 and in our Quarterly Report on Form 10-Q for the quarter ended March
31, 2001, which are incorporated by reference in this prospectus, you should
carefully consider the other information contained or incorporated by reference
in this prospectus, before making an investment decision. The risks and
uncertainties described below and incorporated by reference are not the only
risks we face. Additional risks and uncertainties not presently known to us or
that we currently deem immaterial may impair our business operations.


                      WHERE YOU CAN FIND MORE INFORMATION

     We file annual, quarterly and current reports, proxy statements and other
information with the SEC. You may obtain any document we file with the SEC at
the SEC's public reference rooms in Washington, D.C., Chicago, Illinois and New
York, New York. You may obtain information on the operation of the SEC's public
reference facilities by calling the SEC at 1-800-SEC-0330. You can request
copies of these documents, upon payment of a duplicating fee, by writing to the
SEC at its principal office at 450 Fifth Street, N.W., Washington, D.C.
20549-1004. Our SEC filings are also accessible through the Internet at the
SEC's Web site at http://www.sec.gov.

     The SEC permits us to "incorporate by reference" into this prospectus the
information in documents we file with it, which means that we can disclose
important information to you by referring you to those documents. The
information incorporated by reference is considered to be a part of this
prospectus, and later information that we file with the SEC will update and
supersede this information. We incorporate by reference the documents listed
below and any future filings made with the SEC under Section 13(a), 13(c), 14 or
15(d) of the Securities Exchange Act of 1934, as amended, until the offering is
otherwise terminated:


     - Calpine's Annual Report on Form 10-K for the year ended December 31,
      2000;



     - Calpine's Quarterly Report on Form 10-Q for the quarter ended March 31,
      2001;



     - Calpine's Current Reports on Form 8-K dated February 6, 2001, April 9,
      2001, April 19, 2001, April 26, 2001, June 26, 2001, July 6, 2001, July
      12, 2001, July 16, 2001 and July 26, 2001.



     - the description of Calpine's common stock contained in Calpine's
      Registration Statement on Form 8-A (File No. 001-12079), filed with the
      SEC on August 20, 1996, pursuant to Section 12 of the Securities Exchange
      Act of 1934, as amended.


     If you request a copy of any or all of the documents incorporated by
reference, then we will send to you the copies you requested at no charge.
However, we will not send exhibits to such documents, unless such exhibits are
specifically incorporated by reference in such documents. You should direct
requests for such copies to Calpine Corporation, 50 West San Fernando Street,
San Jose, California 95113, attention: Lisa M. Bodensteiner, Assistant
Secretary, telephone: (408) 995-5115.

     We have filed with the SEC a registration statement on Form S-3 under the
Securities Act, covering the securities described in this prospectus. This
prospectus does not contain all of the information included in the registration
statement. Any statement made in this prospectus concerning the contents of any
contract, agreement or other document is only a summary of the actual contract,
agreement or other document. If we have filed any contract, agreement or other
document as an exhibit to the registration statement, you should read the
exhibit for a more complete understanding of the document or matter involved.
Each statement regarding a contract, agreement or other document is qualified in
its entirety by reference to the actual document.

                                        9
<PAGE>   13

                           FORWARD-LOOKING STATEMENTS

     Some of the statements contained in this prospectus and incorporated by
reference into this prospectus are forward-looking statements within the meaning
of Section 27A of the Securities Act and Section 21E of the Securities Exchange
Act and are subject to the safe harbor created by the Private Securities
Litigation Reform Act of 1995. These statements include declarations regarding
our or our management's intents, beliefs or current expectations. In some cases,
you can identify forward-looking statements by terminology such as "may,"
"will," "should," "expects," "plans," "anticipates," "believes," "estimates,"
"predicts," "potential," or "continue" or the negative of such terms or other
comparable terminology. Any forward-looking statements are not guarantees of
future performance and actual results could differ materially from those
indicated by the forward-looking statements. Forward-looking statements involve
known and unknown risks, uncertainties, and other factors that may cause our or
our industry's actual results, levels of activity, performance, or achievements
to be materially different from any future results, levels of activity,
performance, or achievements expressed or implied by such forward-looking
statements.

     Among the important factors that could cause actual results to differ
materially from those indicated by such forward-looking statements are:

     - changes in government regulations, including pending changes in
       California, and anticipated deregulation of the electric energy industry;

     - commercial operations of new plants that may be delayed or prevented
       because of various development and construction risks, such as a failure
       to obtain financing and the necessary permits to operate or the failure
       of third-party contractors to perform their contractual obligations;

     - cost estimates are preliminary and actual costs may be higher than
       estimated;

     - the assurance that the Company will develop additional plants;

     - a competitor's development of a lower-cost generating gas-fired power
       plant;

     - the risks associated with marketing and selling power from power plants
       in the newly competitive energy market;

     - the risks associated with marketing and selling combustion turbine parts
       and components in the competitive combustion turbine parts market;

     - the risks associated with engineering, designing and manufacturing
       combustion turbine parts and components;

     - delivery and performance risks associated with combustion turbine parts
       and components attributable to production, quality control, suppliers and
       transportation;

     - the successful exploitation of an oil or gas resource that ultimately
       depends upon the geology of the resource, the total amount and cost to
       develop recoverable reserves, and operational factors relating to the
       extraction of natural gas;


     - the uncertainty of the California power market. We are working closely
       with a number of parties to resolve the current uncertainty. This is an
       ongoing process and, therefore, the outcome cannot be predicted. It is
       possible that any such outcome will include changes in government
       regulations, business and contractual relationships or other factors that
       could materially affect us; however, we believe that a final resolution
       will not have a material adverse impact on us; and



     - other risks identified from time to time in our reports and registration
       statements filed with the SEC, including the risk factors identified in
       "Risk Factors" and in our Annual Report on Form 10-K for the year ended
       December 31, 2000 and Quarterly Report on Form 10-Q for the quarter ended
       March 31, 2001, which are incorporated by reference in this prospectus.


                                        10
<PAGE>   14

     Although we believe that the expectations reflected in the forward-looking
statements are reasonable, we cannot guarantee future results, levels of
activity, performance, or achievements. Moreover, neither we nor any other
person assumes responsibility for the accuracy and completeness of such
statements. We are under no duty to update any of the forward-looking statements
after the date of this prospectus to conform such statements to actual results.

                                USE OF PROCEEDS

     We will not receive any cash proceeds upon the resale of our common stock
registered by this prospectus. The selling holders will receive all of the net
proceeds of the resales.

                                SELLING HOLDERS


     The selling holders may from time to time offer and sell pursuant to this
prospectus any or all of the shares of common stock listed below. The selling
holders may also elect not to sell any common stock held by them. The term
"selling holders" refers to the holders listed below. Only those shares of
common stock listed below may be offered for resale by the selling holders
pursuant to this prospectus.


     The selling holders may offer and sell any or all of the common stock
listed below by using this prospectus. Because the selling holders may offer all
or only some portion of the common stock listed in the table, no estimate can be
given as to the amount or percentage of these shares of common stock that will
be held by the selling holders upon termination of this offering. In addition,
the selling holders may have sold, transferred or otherwise disposed of all or a
portion of their shares since the date on which they provided the information
regarding their ownership of the common stock included herein.

     The following table sets forth information with respect to the number of
shares of common stock beneficially owned by the selling holders that may be
offered for the selling holders' accounts pursuant to this prospectus. We
prepared the table based on information supplied to us by the selling holders.

<Table>
<Caption>
                                          NUMBER OF SHARES OF
        NUMBER OF SHARES OF
                                              COMMON STOCK
           COMMON STOCK
                                           BENEFICIALLY OWNED       NUMBER OF
SHARES     BENEFICIALLY OWNED
           SELLING HOLDERS              PRIOR TO THE OFFERING(1)    BEING
OFFERED(1)    AFTER THE OFFERING(1)
           ---------------              ------------------------
----------------    ---------------------
<S>                                     <C>                         <C>
       <C>
Michael Rojansky......................           37,794                  37,794
                 0
James R. Rowland & Elizabeth J.
  Brusnahan...........................           15,117                  15,117
                 0
Patrick H. Ryan.......................           15,117                  15,117
                 0
David W. Winn.........................           83,148                  83,148
                 0
</Table>

-------------------------
(1) Beneficial ownership is determined in accordance with the rules of the SEC
    and generally includes voting or investment power with respect to
    securities. The selling holders have sole voting and sole investment power
    with respect to all shares beneficially owned, subject to community property
    laws, where applicable. For purposes of this table, we have assumed that the
    selling holders will offer and sell all of the shares of our common stock
    they receive upon the exchange of their WRMS shares, however, the selling
    holders may offer and/or sell less than all of such shares of common stock.


     On April 13, 2001, certain of the selling holders entered into employment
agreements with us. David Winn became a Senior Vice President of Calpine and
Patrick Ryan, Michael Rojansky and James Rowland each became Vice Presidents of
Calpine. The selling holders are also officers of our affiliate WRMS. David Winn
is President of WRMS and Michael Rojansky is Chief Operating Officer of WRMS.
James Rowland and Patrick Ryan are both Vice Presidents of WRMS.


     To our knowledge, other than their stock ownership described in the above
table and their employment with us and WRMS described above, the selling holders
have had no position, office or material relationship with Calpine or any of its
predecessors or affiliates within the past three years.

                                        11
<PAGE>   15

                              PLAN OF DISTRIBUTION

     The selling holders may offer and sell the shares of our common stock
referred to above under "Selling Holders" from time to time directly to
purchasers. Alternatively, the selling holders may from time to time offer those
shares of common stock to or through underwriters, broker-dealers or agents, who
may receive compensation in the form of underwriting discounts, concessions or
commissions from the selling holders or the purchasers of the common stock for
whom they act as agents. The selling holders and any underwriters,
broker-dealers or agents that participate in the distribution of the common
stock may be deemed to be "underwriters" within the meaning of the Securities
Act, and any profit on the sale of such common stock and any discounts,
commissions, concessions or other compensation received by any such underwriter,
broker-dealer or agent may be deemed to be underwriting discounts and
commissions under the Securities Act.

     The selling holders' common stock may be sold from time to time in one or
more transactions at fixed prices, at prevailing market prices at the time of
sale, at varying prices determined at the time of sale or at negotiated prices.
The sale of the common stock may be effected in transactions, which may involve
crosses or block transactions:

     - on any national securities exchange or quotation service on which the
       common stock may be listed or quoted at the time of sale,

     - in the over-the-counter market,

     - in transactions otherwise than on such exchanges or in the
       over-the-counter market, or

     - through the writing and exercise of options.

     At the time a particular offering of the common stock is made by the
selling holders, such selling holders must provide a copy of this prospectus,
which sets forth the name of the selling holders and the aggregate amount of
common stock being offered. To comply with the securities laws of certain
jurisdictions, if applicable, the common stock will be offered or sold in such
jurisdictions only through registered or licensed brokers or dealers.

     We have borne all fees and expenses incurred in connection with the
registration of the common stock. The selling holders will pay all expenses
incident to the offer and sale of the common stock, including any underwriting
discounts, selling commissions or fees, stock transfer taxes or similar costs.

                        DESCRIPTION OF OUR CAPITAL STOCK


     Calpine's authorized capital stock consists of 1,000,000,000 shares of
common stock, $.001 par value, and 10,000,000 shares of preferred stock, $.001
par value. The following summary is qualified in its entirety by the provisions
of Calpine's certificate of incorporation and by-laws, which have been
incorporated by reference as exhibits to the Registration Statement of which
this prospectus constitutes a part. The information provided below reflects the
2 for 1 split of Calpine's common stock that became effective on October 7,
1999, the 2 for 1 split of Calpine's common stock that became effective on June
8, 2000 and the 2 for 1 split of Calpine's common stock that became effective on
November 14, 2000.


COMMON STOCK


     The holders of common stock are entitled to one vote per share on all
matters to be voted upon by stockholders. Subject to preferences that may be
applicable to any outstanding preferred stock, the holders of common stock are
entitled to receive ratably such dividends, if any, as may be declared from time
to time by the board of directors out of legally available funds. See "Dividend
Policy." In the event of our liquidation, dissolution or winding up, the holders
of common stock are entitled to share ratably in all assets remaining after
payment of liabilities, subject to prior liquidation rights of preferred stock,
if any, then outstanding. The common stock has no preemptive or conversion
rights or other subscription rights. There are no redemption or sinking fund
provisions applicable to the common stock. Pursuant to a rights


                                        12
<PAGE>   16

agreement entered into in June of 1997, our shares of common stock outstanding
prior to the occurrence of events specified in the rights agreement have certain
preferred share purchase rights, which are set forth in more detail in the
rights agreement incorporated by reference as an exhibit to the Registration
Statement of which this prospectus constitutes a part. See "-- Anti-Takeover
Effects of Provisions of the Certificate of Incorporation, Bylaws, Rights Plan
and Delaware Law -- Rights Plan."

PRICE RANGE OF COMMON STOCK

     Our common stock is traded on The New York Stock Exchange under the symbol
"CPN." Public trading of the common stock commenced on September 20, 1996. Prior
to that, there was no public market for the common stock. The following table
sets forth, for the periods indicated, the high and low sale price per share of
the common stock on The New York Stock Exchange.


<Table>
<Caption>
                                                            HIGH        LOW
                                                           -------    -------
<S>                                                        <C>        <C>
1999
First Quarter............................................  $ 4.672    $ 3.157
Second Quarter...........................................    7.375      4.391
Third Quarter............................................   11.969      6.852
Fourth Quarter...........................................   16.375     10.633
2000
First Quarter............................................  $30.750    $16.094
Second Quarter...........................................   35.219     18.125
Third Quarter............................................   52.250     32.250
Fourth Quarter...........................................   52.969     32.250
2001
First Quarter............................................  $ 58.04    $ 29.00
Second Quarter...........................................    57.35      36.20
Third Quarter (through July 27, 2001)....................    46.00      32.50
</Table>



     As of July 27, 2001, there were approximately 844 holders of record of our
common stock. On July 27, 2001, the last sale price reported on The New York
Stock Exchange for our common stock was $37.90 per share.


DIVIDEND POLICY


     We do not anticipate paying any cash dividends on our common stock in the
foreseeable future because we intend to retain our earnings to finance the
expansion of our business and for general corporate purposes. In addition, our
ability to pay cash dividends is restricted under certain of our indentures and
our other debt agreements. Future cash dividends, if any, will be at the
discretion of our board of directors and will depend upon, among other things,
our future operations and earnings, capital requirements, general financial
condition, contractual restrictions and such other factors as the board of
directors may deem relevant.


PREFERRED STOCK


     As of July 27, 2001, there was one share of preferred stock outstanding.
The board of directors has the authority, without further vote or action by our
stockholders, to issue from time to time up to 10,000,000 shares of preferred
stock in one or more series, and to fix the rights, preferences, privileges,
qualifications, limitations and restrictions granted to or imposed upon any
wholly unissued shares of undesignated preferred stock, including without
limitation dividend rights, if any, voting rights, if any, and liquidation and
conversion rights, if any. The board of directors has the authority to fix the
number of shares constituting any series and the designations of such series
without any further vote or action by our stockholders. The board of directors,
without stockholder approval, can issue preferred stock with voting and
conversion rights which could adversely affect the voting power of the holders
of our common stock. The issuance of preferred stock may have the effect of
delaying, deferring or preventing a change in


                                        13
<PAGE>   17

control of our company, or could delay or prevent a transaction that might
otherwise give our stockholders an opportunity to realize a premium over the
then prevailing market price of the common stock.


     Calpine's board of directors has authorized the issuance of up to 1,000,000
shares of Series A Participating Preferred Stock, par value $.001 per share,
pursuant to a rights plan adopted by Calpine's board of directors on June 5,
1997. As of July 27, 2001, no shares of Calpine's participating preferred stock
were outstanding. A description of the rights plan and the participating
preferred stock is set forth under "-- Anti-Takeover Effects of Provisions of
the Certificate of Incorporation, Bylaws, Rights Plan and Delaware -- Rights
Plan," below.



     Upon consummation of the Encal acquisition, a series of preferred stock of
Calpine, consisting of one share, was designated as special voting preferred
stock of Calpine, having a par value of $.001 per share, and a liquidation
preference of $.001. Except as otherwise required by law or our certificate of
incorporation, the one share of special voting preferred stock possesses a
number of votes for the election of directors and on all other matters submitted
to a vote of our stockholders equal to the number of outstanding Calpine common
equivalent shares issued by our wholly owned subsidiary from time to time and
not owned by us or any entity controlled by us. The holders of our common stock
and the holder of our special voting preferred stock vote together as a single
class on all matters on which holders of our common stock are eligible to vote.
In the event of our liquidation, dissolution or winding-up, all outstanding
Calpine common equivalent shares will automatically be exchanged for shares of
our common stock, and the holders of special voting preferred stock will not be
entitled to receive any of our assets available for distribution to our
stockholders. The holder of special voting preferred stock will not be entitled
to receive dividends. The share of special voting preferred stock was issued to
CIBC Mellon Trust Company, as trustee under a voting and exchange trust
agreement among us, Calpine Canada and the trustee. At such time as the one
share of special voting preferred stock has no votes attached to it because
there are no Calpine common equivalent shares outstanding not owned by us or an
entity controlled by us, the one share of special voting preferred stock will be
canceled.


ANTI-TAKEOVER EFFECTS OF PROVISIONS OF THE CERTIFICATE OF INCORPORATION,
BY-LAWS, RIGHTS PLAN AND DELAWARE LAW

CERTIFICATE OF INCORPORATION AND BY-LAWS


     Our certificate of incorporation and by-laws provide that our board of
directors is classified into three classes of directors serving staggered,
three-year terms. The certificate of incorporation also provides that directors
may be removed only by the affirmative vote of the holders of two-thirds of the
shares of our capital stock entitled to vote, voting together as a single class.
Any vacancy on the board of directors may be filled only by vote of the majority
of directors then in office. Further, the certificate of incorporation provides
that any business combination (as defined therein) requires the affirmative vote
of the holders of two-thirds of the shares of our capital stock entitled to
vote, voting together as a single class. The certificate of incorporation also
provides that all stockholder actions must be effected at a duly called meeting
and not by a consent in writing. The by-laws provide that our stockholders may
call a special meeting of stockholders only upon a request of stockholders
owning at least 50% of Calpine's capital stock. These provisions of the
certificate of incorporation and by-laws could discourage potential acquisition
proposals and could delay or prevent a change in control of our company. These
provisions are intended to enhance the likelihood of continuity and stability in
the composition of the board of directors and in the policies formulated by the
board of directors and to discourage certain types of transactions that may
involve an actual or threatened change of control of our company. These
provisions are designed to reduce our vulnerability to an unsolicited
acquisition proposal. The provisions also are intended to discourage certain
tactics that may be used in proxy fights. However, such provisions could have
the effect of discouraging others from making tender offers for our shares and,
as a consequence, they also may inhibit fluctuations in the market price of our
shares that could result from actual or rumored takeover attempts. Such
provisions also may have the effect of preventing changes in our management.


                                        14
<PAGE>   18

     Rights Plan. On June 5, 1997, we adopted a stockholders' rights plan to
strengthen our ability to protect our stockholders. The rights plan is designed
to protect against abusive or coercive takeover tactics that are not in the best
interests of Calpine or its stockholders. To implement the rights plan, we
declared a dividend of one preferred share purchase right for each outstanding
share of our common stock held on record as of June 18, 1997, and directed the
issuance of one preferred share purchase right with respect to each share of our
common stock that shall become outstanding thereafter until the rights become
exercisable or they expire as described below. Each right initially represents a
contingent right to purchase, under certain circumstances, one one-thousandth of
a share, called a "unit," of our Series A Participating Preferred Stock, par
value $.001 per share, at a price of $80.00 per unit, subject to adjustment. The
rights become exercisable and trade independently from our common stock upon the
public announcement of the acquisition by a person or group of 15% or more of
our common stock, or ten days after commencement of a tender or exchange offer
that would result in the acquisition of 15% or more of our common stock. Each
unit purchased upon exercise of the rights will be entitled to a dividend equal
to any dividend declared per share of common stock and will have one vote,
voting together with the common stock. In the event of our liquidation, each
share of the participating preferred stock will be entitled to any payment made
per share of common stock.

     If we are acquired in a merger or other business combination transaction
after a person or group has acquired 15% or more of our common stock, each right
will entitle its holder to purchase at the right's exercise price a number of
the acquiring company's shares of common stock having a market value of twice
the right's exercise price. In addition, if a person or group acquires 15% or
more of our common stock, each right will entitle its holder (other than the
acquiring person or group) to purchase, at the right's exercise price, a number
of fractional shares of our participating preferred stock or shares of our
common stock having a market value of twice the right's exercise price.

     The rights expire on June 18, 2007, unless redeemed earlier by us. We can
redeem the rights at a price of $.01 per right at any time before the rights
become exercisable, and thereafter only in limited circumstances.

DELAWARE ANTI-TAKEOVER STATUTE

     We are subject to Section 203 of the Delaware General Corporation Law
("Section 203"), which, subject to certain exceptions, prohibits a Delaware
corporation from engaging in any business combination with any interested
stockholder for a period of three years following the date that such stockholder
became an interested stockholder, unless: (1) prior to such date, the board of
directors of the corporation approved either the business combination or the
transaction that resulted in the stockholder becoming an interested stockholder;
(2) upon consummation of the transaction that resulted in the stockholder
becoming an interested stockholder, the interested stockholder owned at least
85% of the voting stock of the corporation outstanding at the time the
transaction commenced, excluding for purposes of determining the number of
shares outstanding those shares owned (x) by persons who are directors and also
officers and (y) by employee stock plans in which employee participants do not
have the right to determine confidentially whether shares held subject to the
plan will be tendered in a tender or exchange offer; or (3) on or subsequent to
such date, the business combination is approved by the board of directors and
authorized at an annual or special meeting of stockholders, and not by written
consent, by the affirmative vote of at least 66 2/3% of the outstanding voting
stock that is not owned by the interested stockholder.

     Section 203 defines business combination to include: (1) any merger or
consolidation involving the corporation or any of its direct or indirect
majority-owned subsidiaries and the interested stockholder; (2) any sale,
transfer, pledge or other disposition of 10% or more of the assets of the
corporation or any of its direct or indirect majority-owned subsidiaries
involving the interested stockholder; (3) subject to certain exceptions, any
transaction that results in the issuance or transfer by the corporation of any
stock of the corporation or any of its direct or indirect majority-owned
subsidiaries of any stock of the corporation or that subsidiary to the
interested stockholder; (4) any transaction involving the corporation or any of
its direct or indirect majority-owned subsidiaries that has the effect of
increasing the proportionate share of the stock of any class or series of the
corporation or that subsidiary beneficially owned by the interested
                                        15
<PAGE>   19

stockholder; or (5) the receipt by the interested stockholder of the benefit of
any loans, advances, guarantees, pledges or other financial benefits provided by
or through the corporation or any of its direct or indirect majority-owned
subsidiaries. In general, Section 203 defines an interested stockholder as any
entity or person beneficially owning 15% or more of the outstanding voting stock
of the corporation and any entity or person affiliated with or controlling or
controlled by such entity or person.

             CERTAIN UNITED STATES FEDERAL INCOME TAX CONSEQUENCES


     The following is a summary of the material United States federal income tax
consequences of the purchase, ownership and disposition of Calpine's common
stock. Unless otherwise stated, this summary deals only with common stock held
as capital assets by U.S. holders. As used herein, "U.S. holders" are any
beneficial owners of common stock, that are, for United States federal income
tax purposes, (1) citizens or residents of the United States, (2) corporations
created or organized in or under the laws of the United States, any state
thereof or the District of Columbia, (3) estates, the income of which is subject
to United States federal income taxation regardless of its source, or (4) trusts
if in general (A) a court within the United States is able to exercise primary
supervision over the administration of the trust and (B) one or more United
States persons have the authority to control all substantial decisions of the
trust. In addition, certain trusts in existence on August 20, 1996 and treated
as a U.S. holder prior to such date may also be treated as U.S. holders. As used
herein, "non-U.S. holders" are beneficial owners of common stock, other than
partnerships, that are not U.S. holders for United States federal income tax
purposes. If a partnership (including for this purpose any entity treated as a
partnership for United States tax purposes) is a beneficial owner of common
stock, the treatment of a partner in the partnership will generally depend upon
the status of the partner and upon the activities of the partnership. Holders of
common stock that are partnerships, and partners in such partnerships, should
consult their tax advisers about the United States federal income tax
consequences of holding and disposing of the common stock. This summary does not
deal with special classes of holders such as banks, thrifts, real estate
investment trusts, regulated investment companies, insurance companies, dealers
in securities or currencies, or tax-exempt investors and does not discuss common
stock held as part of a hedge, straddle, "synthetic security" or other
integrated transaction. This summary also does not address the tax consequences
to persons that have a functional currency other than the U.S. dollar or the tax
consequences to shareholders, partners or beneficiaries of a holder of the
common stock. Further, it does not include any description of any alternative
minimum tax consequences or the tax laws of any state or local government or of
any foreign government that may be applicable to the common stock. This summary
is based on the Internal Revenue Code of 1986, as amended, the Treasury
regulations promulgated thereunder and administrative and judicial
interpretations thereof, all as of the date hereof, and all of which are subject
to change, possibly on a retroactive basis.


     YOU SHOULD CONSULT WITH YOUR OWN TAX ADVISOR REGARDING THE FEDERAL, STATE,
LOCAL AND FOREIGN INCOME, FRANCHISE, PERSONAL PROPERTY, AND ANY OTHER TAX
CONSEQUENCES OF THE PURCHASE, OWNERSHIP AND DISPOSITION OF CALPINE COMMON STOCK.

U.S. HOLDERS OF COMMON STOCK

Dividends


     The amount of any distribution we make in respect of the common stock will
be equal to the amount of cash and the fair market value, on the date of
distribution, of any property distributed. Generally, distributions will be
treated as a dividend, subject to tax as ordinary income, to the extent of our
current or accumulated earnings and profits, then as a tax-free return of
capital to the extent of a holder's tax basis in the common stock and thereafter
as gain from the sale or exchange of such stock as described below.



     In general, a dividend distribution to a corporate holder will qualify for
the 70% dividends-received deduction. The dividends received deduction is
subject to certain holding period, taxable income, and other limitations.


                                        16
<PAGE>   20

Sale or Exchange of Common Stock


     Upon the sale or exchange of common stock, a holder generally will
recognize capital gain or loss equal to the difference between (1) the amount of
cash and the fair market value of any property received upon the sale or
exchange and (2) such holder's adjusted tax basis in the common stock. In the
case of a holder other than a corporation, the preferential tax rates may apply
to such gain if such holder's holding period for such common stock exceeds one
year. A holder's basis in the common stock is generally equal to its initial
purchase price.


Information Reporting and Backup Withholding Tax


     In general, information reporting requirements will apply to payments of
dividends on common stock and payments of the proceeds of the sale of common
stock, and a backup withholding tax (currently 30.5%) may apply to such payments
if the holder fails to comply with certain identification requirements. Any
amounts withheld under the backup withholding rules from a payment to a holder
will be allowed as a credit against such holder's United States federal income
tax and may entitle the holder to a refund, provided that the required
information is furnished to the Internal Revenue Service.


NON-U.S. HOLDERS OF COMMON STOCK

     The rules governing United States federal income taxation of a beneficial
owner of common stock that is a non-U.S. holder are complex and no attempt will
be made herein to provide more than a summary of such rules. Non-U.S. holders
should consult with their own tax advisors to determine the effect of federal,
state, local and foreign income tax laws, as well as treaties, with regard to an
investment in the common stock, including any reporting requirements.

Dividends

     Distributions by us with respect to the common stock that are treated as
dividends paid (or deemed paid), as described above under "Dividends," to a
non-U.S. holder (excluding dividends that are effectively connected with the
conduct of a United States trade or business by such holder and are taxable as
described below) will be subject to United States federal withholding tax at a
30% rate (or a lower rate provided under any applicable income tax treaty).
Except to the extent that an applicable tax treaty otherwise provides, a
non-U.S. holder will be taxed in the same manner as a U.S. holder on dividends
paid (or deemed paid) that are effectively connected with the conduct of a
United States trade or business by the non-U.S. holder. If such non-U.S. holder
is a foreign corporation, it may also be subject to a United States branch
profits tax on such effectively connected income at a 30% rate (or such lower
rate as may be specified by an applicable tax treaty). Even though such
effectively connected dividends are subject to income tax and may be subject to
the branch profits tax, they will not be subject to United States federal
withholding tax if the holder delivers a properly executed Internal Revenue
Service Form W-8ECI (or successor form) to the payor.

     A non-U.S. holder who wishes to claim the benefit of an applicable treaty
rate is required to satisfy applicable certification and other requirements. If
you are eligible for a reduced rate of United States federal withholding tax
pursuant to an income tax treaty, you may obtain a refund of any excess amounts
withheld by filing an appropriate claim for refund with the Internal Revenue
Service.

Sale or Exchange of Common Stock


     A non-U.S. holder generally will not be subject to United States federal
income tax or withholding tax on the sale or exchange of common stock unless (1)
the gain is effectively connected with a United States trade or business of the
non-U.S. holder, (2) in the case of a non-U.S. holder who is an individual, such
holder is present in the United States for a period or periods aggregating 183
days or more during the taxable year of the disposition, and either (A) such
holder has a "tax home" in the United States or (B) the disposition is
attributable to an office or other fixed place of business maintained by such
holder in the United States, (3) the non-U.S. holder is subject to tax pursuant
to the provisions of the Internal

                                        17
<PAGE>   21

Revenue Code applicable to certain United States expatriates or (4) in the event
that Calpine is characterized as a United States real property holding
corporation (see discussion below under "Foreign Investment in Real Property Tax
Act"), the non-U.S. holder's beneficial and/or constructive ownership of common
stock exceeds 5% of the total fair market value of the common stock.

Information Reporting and Backup Withholding Tax


     United States information reporting requirements and backup withholding tax
will not apply to any payment of the proceeds of the sale of common stock
effected outside the United States by a foreign office of a "broker" as defined
in applicable Treasury regulations, unless such broker (1) is a United States
person as defined in the Internal Revenue Code, (2) is a foreign person that
derives 50% or more of its gross income for certain periods from the conduct of
a trade or business in the United States, (3) is a controlled foreign
corporation for United States federal income tax purposes or (4) is a foreign
partnership with certain U.S. connections. Payment of the proceeds of any such
sale effected outside the United States by a foreign office of any broker that
is described in the preceding sentence may be subject to backup withholding tax
and information reporting requirements, unless such broker has documentary
evidence in its records that the beneficial owner is a non-U.S. holder and
certain other conditions are met, or the beneficial owner otherwise establishes
an exemption. Dividends on common stock held by a non-U.S. holder will be
subject to information reporting requirements and may be subject to backup
withholding requirements unless certain certification requirements are
satisfied.


Foreign Investment in Real Property Tax Act


     Under the Foreign Investment in Real Property Tax Act, any person who
acquires a "United States real property interest" (as described below) from a
foreign person must deduct and withhold a tax equal to 10% of the amount
realized by the foreign transferor. In addition, a foreign person who disposes
of a United States real property interest generally is required to recognize
gain or loss that is subject to United States federal income tax. A "United
States real property interest" generally includes any interest (other than an
interest solely as a creditor) in a United States corporation unless it is
established under specific procedures that the corporation is not (and was not
for the prior five-year period) a "United States real property holding
corporation." We believe it is likely that we are a "United States real property
holding corporation" and we can give no assurance that we will not continue to
be classified as a United States real property holding corporation in the
future. However, so long as our stock is regularly traded on an established
securities market, an exemption applies with respect to any non-U.S. holder
whose beneficial and/or constructive ownership of common stock is 5% or less of
the total fair market value of the common stock. Any investor that may approach
or exceed the 5% ownership threshold discussed above, either alone or in
conjunction with related persons, should consult its own tax advisor concerning
the United States tax consequences that may result. A non-U.S. holder who sells
or otherwise disposes of common stock may be required to inform its transferee
whether such common stock constitutes a United States real property interest.


     THE UNITED STATES FEDERAL INCOME TAX DISCUSSION SET FORTH ABOVE IS INCLUDED
FOR GENERAL INFORMATION ONLY AND MAY NOT BE APPLICABLE DEPENDING UPON A HOLDER'S
PARTICULAR SITUATION. HOLDERS SHOULD CONSULT THEIR TAX ADVISORS WITH RESPECT TO
THE TAX CONSEQUENCES TO THEM OF THE PURCHASE, OWNERSHIP AND DISPOSITION OF
COMMON STOCK, INCLUDING THE TAX CONSEQUENCES UNDER STATE, LOCAL, FOREIGN AND
OTHER TAX LAWS AND THE POSSIBLE EFFECTS OF CHANGES IN UNITED STATES FEDERAL OR
OTHER TAX LAWS.

                                 LEGAL MATTERS


     The validity of the shares of our common stock offered hereby will be
passed upon for us by Covington & Burling, New York, New York.


                                        18
<PAGE>   22

                         INDEPENDENT PUBLIC ACCOUNTANTS

     Calpine's audited financial statements incorporated by reference in this
prospectus have been audited by Arthur Andersen LLP, independent public
accountants, as indicated in their reports with respect thereto, and are
included herein in reliance upon the authority of said firm as experts in giving
such reports.

                                        19
<PAGE>   23

                                    PART II

                     INFORMATION NOT REQUIRED IN PROSPECTUS

ITEM 14. OTHER EXPENSES OF ISSUANCE AND DISTRIBUTION.

     The following table sets forth the costs and expenses payable by Calpine in
connection with issuance and distribution of the securities being registered.
All amounts are estimates subject to future contingencies except the SEC
registration statement filing fee.

<Table>
<S>                                                           <C>
SEC registration statement filing fee.......................  $  2,095
Accounting fees and expenses................................    25,000
Legal fees and expenses.....................................    25,000
Printing fees...............................................    25,000
Transfer agent fees.........................................     5,000
Miscellaneous...............................................    17,905
                                                              --------
  Total.....................................................  $100,000
                                                              ========
</Table>

ITEM 15. INDEMNIFICATION OF DIRECTORS AND OFFICERS.

     Section 145 of the General Corporation Law of the State of Delaware (the
"Delaware Law") empowers a Delaware corporation to indemnify any persons who
are, or are threatened to be made, parties to any threatened, pending or
completed legal action, suit or proceedings, whether civil, criminal,
administrative or investigative (other than action by or in the right of such
corporation), by reason of the fact that such person was an officer or director
of such corporation, or is or was serving at the request of such corporation as
a director, officer, employee or agent of another corporation or enterprise. The
indemnity may include expenses (including attorneys' fees), judgments, fines and
amounts paid in settlement actually and reasonably incurred by such person in
connection with such action, suit or proceeding, provided that such officer or
director acted in good faith and in a manner he reasonably believed to be in or
not opposed to the corporation's best interests, and, for criminal proceedings,
had no reasonable cause to believe his conduct was unlawful. A Delaware
corporation may indemnify officers and directors in an action by or in the right
of the corporation under the same conditions, except that no indemnification is
permitted without judicial approval if the officer or director is adjudged to be
liable to the corporation in the performance of his duty. Where an officer or
director is successful on the merits or otherwise in the defense of any action
referred to above, the corporation must indemnify him against the expenses which
such officer or director actually and reasonably incurred.

     In accordance with Delaware Law, the certificate of incorporation of
Calpine contains a provision to limit the personal liability of the directors of
Calpine for violations of their fiduciary duty. This provision eliminates each
director's liability to Calpine or its stockholders for monetary damages except
(i) for any breach of the director's duty of loyalty to Calpine or its
stockholders, (ii) for acts or omissions not in good faith or which involve
intentional misconduct or a knowing violation of law, (iii) under Section 174 of
the Delaware Law providing for liability of directors for unlawful payment of
dividends or unlawful stock purchases or redemptions, or (iv) for any
transaction from which a director derived an improper personal benefit. The
effect of this provision is to eliminate the personal liability of directors for
monetary damages for actions involving a breach of their fiduciary duty of care,
including any such actions involving gross negligence. The certificate of
incorporation further provides that, if the Delaware Law is amended to further
reduce the liability of a corporation's directors for breaches of fiduciary
duty, then a director of Calpine shall not be liable for any such breach to the
fullest extent permitted by the law as so amended.

     Article Ten of the bylaws of Calpine provides for indemnification of the
officers and directors of Calpine to the fullest extent permitted by applicable
law.

     Calpine has entered into indemnification agreements with its directors and
officers. These agreements provide substantially broader indemnity rights than
those provided under the Delaware Law and Calpine's

                                       II-1
<PAGE>   24

bylaws. The indemnification agreements are not intended to deny or otherwise
limit third-party or derivative suits against Calpine or its directors or
officers, but if a director or officer were entitled to indemnity or
contribution under the indemnification agreement, the financial burden of a
third-party suit would be borne by Calpine, and Calpine would not benefit from
derivative recoveries against the director or officer. Such recoveries would
accrue to the benefit of Calpine but would be offset by Calpine's obligations to
the director or officer under the indemnification agreement. In addition, the
directors of Calpine are insured under officers and directors liability
insurance policies.

ITEM 16. EXHIBITS


<Table>
<Caption>
EXHIBIT
NUMBER                            DESCRIPTION
-------                           -----------
<C>       <S>
   3.1    Amended and Restated Certificate of Incorporation of Calpine
          Corporation(a)
   3.2    Certificate of Correction of Calpine Corporation(b)
   3.3    Certificate of Amendment of Amended and Restated Certificate
          of Incorporation of Calpine Corporation(c)
   3.4    Certificate of Designation of Series A Participating
          Preferred Stock of Calpine Corporation(b)
   3.5    Amended Certificate of Designation of Series A Participating
          Preferred Stock of Calpine Corporation(b)
   3.6    Amended Certificate of Designation of Series A Participating
          Preferred Stock of Calpine Corporation(c)
   3.7    Certificate of Designation of Special Voting Preferred Stock
          of Calpine Corporation(d)
   3.8    Amended and Restated By-laws of Calpine Corporation(e)
   4.1    Rights Agreement, dated as of June 5, 1997, between Calpine
          Corporation and First Chicago Trust Company of New York as
          rights agent(f)
  +4.2    Registration Rights Agreement, dated as of April 3, 2001,
          between Calpine Corporation and the parties listed on
          Schedule I
  +5.1    Opinion of Covington & Burling
  23.1    Consent of Arthur Andersen LLP, independent public
          accountants
 +23.2    Consent of Covington & Burling (included in Opinion set
          forth as Item 5.1)
 +24.1    Power of Attorney of Officers and Directors of Calpine
          Corporation (set forth on the signature pages of this
          Registration Statement as initially filed)
</Table>


-------------------------

 +  Previously filed.



(a) Incorporated by reference to Calpine Corporation's Registration Statement on
    Form S-3 (Registration No. 333-40652) filed with the SEC on June 30, 2000.



(b)Incorporated by reference to Calpine Corporation's Annual Report on Form 10-K
   for the year ended December 31, 2000, filed with the SEC on March 15, 2001.



(c) Incorporated by reference to Calpine Corporation's Registration Statement on
    Form S-3 (Registration No. 333-66078) filed with the SEC on July 27, 2001.



(d)Incorporated by reference to Calpine Corporation's Quarterly Report on Form
   10-Q for the quarter ended March 31, 2001, filed with the SEC on May 15,
   2001.



(e) Incorporated by reference to Calpine Corporation's Registration Statement on
    Form S-1 (Registration No. 333-07497) filed with the SEC on August 22, 1996.



(f)  Incorporated by reference to Calpine's Registration Statement on Form 8-A
     filed with the SEC on June 18, 1997 and amended by the Corporation's
     Registration Statement on Form 8-A/A filed with the SEC on June 24, 1997
     (File No. 001-12079).


                                       II-2
<PAGE>   25

ITEM 17. UNDERTAKINGS

     The undersigned registrant hereby undertakes:

          (1) To file, during any period in which offers or sales are being
     made, a post-effective amendment to this registration statement to include
     any material information with respect to the plan of distribution not
     previously disclosed in the registration statement or any material change
     to such information in the registration statement.

          (2) That, for the purpose of determining any liability under the
     Securities Act of 1933, each such post-effective amendment shall be deemed
     to be a new registration statement relating to the securities offered
     therein, and the offering of such securities at that time shall be deemed
     to be the initial bona fide offering thereof.

          (3) To remove from registration by means of a post-effective amendment
     any of the securities being registered which remain unsold at the
     termination of the offering.

          (4) If the registrant is a foreign private issuer, to file a
     post-effective amendment to the registration statement to include any
     financial statements required by Rule 3-19 of this chapter at the start of
     any delayed offering or throughout a continuous offering. Financial
     statements and information otherwise required by Section 10(a)(3) of the
     Act need not be furnished, provided, that the registrant includes in the
     prospectus, by means of a post-effective amendment, financial statements
     required pursuant to this paragraph (a)(4) and other information necessary
     to ensure that all other information in the prospectus is at least as
     current as the date of those financial statements. Notwithstanding the
     foregoing, with respect to registration statements on Form F-3, a
     post-effective amendment need not be filed to include financial statements
     and information required by Section 10(a)(3) of the Act or Rule 3-19 of
     this chapter if such financial statements and information are contained in
     periodic reports filed with or furnished to the Commission by the
     registrant pursuant to Section 13 or Section 15(d) of the Securities
     Exchange Act of 1934 that are incorporated by reference in the Form F-3.

     The undersigned registrant hereby undertakes that, for purposes of
determining any liability under the Securities Act of 1933, each filing of the
registrant's annual report pursuant to Section 13(a) or Section 15(d) of the
Securities Exchange Act of 1934, (and, where applicable, each filing of an
employee benefit plan's annual report pursuant to Section 15(d) of the
Securities Exchange Act of 1934) that is incorporated by reference in the
registration statement shall be deemed to be a new registration statement
relating to the securities offered therein, and the offering of such securities
at that time shall be deemed to be the initial bona fide offering thereof.

     The undersigned registrant hereby undertakes to deliver or cause to be
delivered with the prospectus, to each person to whom the prospectus is sent or
given, the latest annual report, to security holders that is incorporated by
reference in the prospectus and furnished pursuant to and meeting the
requirements of Rule 14a-3 under Rule 14c-3 under the Securities Exchange Act of
1934; and, where interim financial information required to be presented by
Article 3 of Regulation S-X is not set forth in the prospectus, to deliver, or
cause to be delivered to each person to whom the prospectus is sent or given,
the latest quarterly report that is specifically incorporated by reference in
the prospectus to provide such interim financial information.

     Insofar as indemnification for liabilities arising under the Securities Act
of 1933 may be permitted to directors, officers and controlling persons of the
registrant pursuant to the foregoing provisions, or otherwise, the registrant
has been advised that in the opinion of the SEC such indemnification is against
public policy as expressed in the Securities Act of 1933 and is, therefore,
unenforceable. In the event that a claim for indemnification against such
liabilities (other than the payment by the registrant of expenses incurred or
paid by a director, officer or controlling person of the registrant in the
successful defense of any action, suit or proceeding) is asserted by such
director, officer or controlling person in connection with the securities being
registered, the registrant will, unless in the opinion of its counsel the matter
has been settled by controlling precedent, submit to a court of appropriate
jurisdiction the question whether such
                                       II-3
<PAGE>   26

indemnification by them is against public policy as expressed in the Securities
Act of 1933 and will be governed by the final adjudication of such issue.

                                       II-4
<PAGE>   27

                                   SIGNATURES


     Pursuant to the requirements of the Securities Act of 1933, the registrant
certifies that it has reasonable grounds to believe that it meets all of the
requirements for filing this Registration Statement on Form S-3 and has duly
caused this Amendment No. 1 to the Registration Statement to be signed on its
behalf by the undersigned, thereunto duly authorized in the City of San Jose,
State of California, on this 27th day of July, 2001.


                                      CALPINE CORPORATION

                                      By:         /s/ ANN B. CURTIS
                                         ---------------------------------------
                                                      Ann B. Curtis
                                                Executive Vice President
                                               and Chief Financial Officer


     Pursuant to the requirements of the Securities Act of 1933, this Amendment
No. 1 to the Registration Statement on Form S-3 has been signed by the following
persons in the capacities and on the dates indicated.



<Table>
<Caption>
                      SIGNATURE                                      TITLE
             DATE
                      ---------                                      -----
             ----
<C>                                                    <C>
         <S>
                          *                               Chairman, President,
Chief      July 27, 2001
-----------------------------------------------------   Executive Officer and
Director
                  Peter Cartwright

                  /s/ ANN B. CURTIS                     Executive Vice
President, Chief   July 27, 2001
-----------------------------------------------------   Financial Officer and
Director
                    Ann B. Curtis

                          *                             Vice President and
Controller,    July 27, 2001
-----------------------------------------------------      Chief Accounting
Officer
                Charles B. Clark, Jr.
                                                                   Director
-----------------------------------------------------
                   Kenneth T. Derr

                          *                                        Director
         July 27, 2001
-----------------------------------------------------
                  Jeffrey E. Garten
                                                                   Director
-----------------------------------------------------
                  Gerald Greenwald

                          *                                        Director
         July 27, 2001
-----------------------------------------------------
                   Susan C. Schwab

                          *                                        Director
         July 27, 2001
-----------------------------------------------------
                 George J. Stathakis
                                                                   Director
-----------------------------------------------------
                   John O. Wilson

               *By: /s/ ANN B. CURTIS
   ----------------------------------------------
                    Ann B. Curtis
                  Attorney-in-fact
</Table>


                                       II-5
<PAGE>   28

                               INDEX TO EXHIBITS


<Table>
<Caption>
EXHIBIT
NUMBER                             DESCRIPTION
-------                            -----------
<C>        <S>
   3.1     Amended and Restated Certificate of Incorporation of Calpine
           Corporation(a)
   3.2     Certificate of Correction of Calpine Corporation(b)
   3.3     Certificate of Amendment of Amended and Restated Certificate
           of Incorporation of Calpine Corporation(c)
   3.4     Certificate of Designation of Series A Participating
           Preferred Stock of Calpine Corporation(b)
   3.5     Amended Certificate of Designation of Series A Participating
           Preferred Stock of Calpine Corporation(b)
   3.6     Amended Certificate of Designation of Series A Participating
           Preferred Stock of Calpine Corporation(c)
   3.7     Certificate of Designation of Special Voting Preferred Stock
           of Calpine Corporation(d)
   3.8     Amended and Restated By-laws of Calpine Corporation(e)
   4.1     Rights Agreement, dated as of June 5, 1997, between Calpine
           Corporation and First Chicago Trust Company of New York as
           rights agent(f)
  +4.2     Registration Rights Agreement, dated as of April 3, 2001,
           between Calpine Corporation and the parties listed on
           Schedule I
  +5.1     Opinion of Covington & Burling
  23.1     Consent of Arthur Andersen LLP, independent public
           accountants
 +23.2     Consent of Covington & Burling (included in Opinion set
           forth as Item 5.1)
 +24.1     Power of Attorney of Officers and Directors of Calpine
           Corporation (set forth on the signature pages of this
           Registration Statement as initially filed)
</Table>


-------------------------
 +  Previously filed.


(a) Incorporated by reference to Calpine Corporation's Registration Statement on
    Form S-3 (Registration No. 333-40652) filed with the SEC on June 30, 2000.



(b)Incorporated by reference to Calpine Corporation's Annual Report on Form 10-K
   for the year ended December 31, 2000, filed with the SEC on March 15, 2001.



(c) Incorporated by reference to Calpine Corporation's Registration Statement on
    Form S-3 (Registration No. 333-66078) filed with the SEC on July 27, 2001.



(d)Incorporated by reference to Calpine Corporation's Quarterly Report on Form
   10-Q for the quarter ended March 31, 2001, filed with the SEC on May 15,
   2001.



(e) Incorporated by reference to Calpine Corporation's Registration Statement on
    Form S-1 (Registration No. 333-07497) filed with the SEC on August 22, 1996.



(f)  Incorporated by reference to Calpine's Registration Statement on Form 8-A
     filed with the SEC on June 18, 1997 and amended by the Corporation's
     Registration Statement on Form 8-A/A filed with the SEC on June 24, 1997
     (File No. 001-12079).


