                                POWER OF ATTORNEY

                                    EXHIBIT B

         KNOW ALL PERSONS BY THESE PRESENTS, that each of Phoebe Snow
Foundation, Inc. and The Elizabeth R. & William J. Patterson Foundation (each, a
"Grantor") has made, constituted and appointed, and by these presents does make,
constitute and appoint, each of William E. Oberndorf and Kim M. Silva (each an
"Attorney"), the true and lawful agent and attorney-in-fact, with full power of
substitution and resubstitution, of the Grantor, for and in Grantor's name,
place and stead, in any and all capacities, to do all or any of the following
acts, matters and things:

     1.   To sign on behalf of the Grantor statements on Schedule 13D or 13G or
          Forms 3, 4 and 5, or amendments thereto pursuant to Section 13(d) or
          Section 16 under the Securities Exchange Act of 1934.

     2.   To do all such other acts and things as, in such Attorney's
          discretion, he or she deems appropriate or desirable for the purpose
          of filing such statements on Schedule 13D or 13G or Forms 3, 4 and 5,
          or amendments thereto.

     3.   To appoint in writing one or more substitutes who shall have the power
          to act on behalf of the Grantor as if that substitute or those
          substitutes shall have been originally appointed Attorney(s) by this
          Power of Attorney and/or to revoke any such appointment at any time
          without assigning any reason therefor.

         The Grantor hereby ratifies and confirms all that said agents and
attorneys-in-fact or any substitute or substitutes may lawfully do or cause to
be done by virtue hereof. This power of Attorney shall remain in full force and
effect until the undersigned is no longer required to file Forms 3, 4 and 5 or
to file reports under Section 13(d) of the Securities Exchange Act of 1934 with
respect to the undersigned's holdings of and transactions in securities issued
by Calpine Corporation, unless earlier revoked by the undersigned in a signed
writing delivered to the foregoing attorneys-in-fact.

         The words Grantor and Attorney shall include all grantors and attorneys
under this Power of Attorney.


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         IN WITNESS WHEREOF, Grantor duly assents to this Power of Attorney by
his, her or its signature as of the 6th day of October, 2008.

                                             Phoebe Snow Foundation, Inc.

                                             /s/ Phoebe Snow Foundation, Inc.
                                             --------------------------------


                                             The Elizabeth R. & William J.
                                               Patterson Foundation

                                             /s/ The Elizabeth R. & William J.
                                             Patterson Foundation
                                             --------------------------------


