EXHIBIT 10.1



SECOND AMENDMENT

to



POWER SUPPLY AND SERVICE AGREEMENT

between



FIRST CHOICE POWER SPECIAL PURPOSE, L.P.



and



CONSTELLATION ENERGY COMMODITIES GROUP, INC.



This Second Amendment to Power Supply and Service Agreement dated as of August 25, 2004 (Amendment) is by and between First Choice Power
Special Purpose, L.P., a Texas limited partnership (First Choice), and Constellation Energy Commodities Group, Inc., formerly known as Constellation Power Source, Inc., a Delaware corporation (Constellation) (each a
Party and collectively, the Parties). Reference is made to the Power Supply and Service Agreement dated as of December 22, 2003 (Agreement) between First Choice and Constellation. Capitalized terms used herein and
not defined herein shall have the meanings set forth in the Agreement.



WHEREAS, the Parties to the Agreement desire to amend the Agreement to, among other things, modify the procedure set forth in the Agreement for the calculation of Ancillary Service obligations; and



WHEREAS, the Parties desire to amend the Agreement on the terms and
conditions set forth herein;



NOW, THEREFORE, in accordance
with the foregoing and in consideration of the mutual promises, covenants, and agreements set forth herein, and for good and valuable consideration, the receipt and sufficiency of which are hereby acknowledged, the Parties hereby agree as follows:



Section 1. Amendment.



1.1 The Agreement is hereby amended, as follows:



a. Section 6.2(d)(i) of Article Six is replaced in its entirety with the
following:



[***]



---

|[***] | Confidential material omitted and filed separately with the Securities & Exchange Commission.
|----- | ---------------------------------------------------------------------------------------------



1



---

[***]



b. Section 6.2 (f) (i) is replaced with the following and is renumbered as Section 6.2(f):



[***]



c. [***]



d. [***]



1.2 Governing Law. This Amendment shall be governed by and construed in accordance with the laws of the state of Texas.



1.3 Counterparts. This Amendment may be executed in any number of
counterparts, each of which shall be an original, but all of which together shall constitute one instrument.



1.4 Modification. This Amendment, including any exhibits, may only be modified by written agreement duly executed by both Parties.



1.5 Ratification of Terms and Conditions of the Agreement. Except as
expressly amended or waived by this Amendment, the terms and conditions contained in the Agreement remain in full force and effect.



---

|[***] | Confidential material omitted and filed separately with the Securities & Exchange Commission.
|----- | ---------------------------------------------------------------------------------------------



2



---

1.6 Entire Agreement. This Amendment represents the entire agreement of the Parties hereto with
respect to the subject matter hereof, and there are no promises, undertakings, covenants, representations, or warranties by the Parties hereto relative to the subject matter hereof not expressly set forth or referred to herein.



1.7 Headings Not to Affect Meaning. The descriptive headings for the
various articles and sections herein have been inserted for convenience and reference only and shall in no way affect the meaning or interpretation, or modify or restrict any of the terms and provisions hereof.



IN WITNESS WHEREOF, the Parties have executed this Amendment as of the
date first written above.



|                                                                      |  | 
|--------------------------------------------------------------------- |  | 
|FIRST CHOICE POWER SPECIAL PURPOSE, L.P., a Texas limited partnership



|       |  |                                                                                                
|------ |  | -----------------------------------------------------------------------------------------------
|By:    |  | First Choice Special Purpose GP, LLC, a Delaware
limited liability company, its General Partner
|       | 
|By:    |  | /s/ Michelle Trenary                                                                           
|Name:  |  | Michelle Trenary                                                                               
|Title: |  | Director, Wholesale Settlement                                                                 



|                                                                     |  | 
|-------------------------------------------------------------------- |  | 
|CONSTELLATION ENERGY COMMODITIES GROUP, INC., a Delaware corporation



|       |  |                         
|------ |  | ------------------------
|By:    |  | /s/ Stuart R. Rubenstein
|Name:  |  | Stuart R. Rubenstein    
|Title: |  | Chief Operating Officer 



---

|[***] | Confidential material omitted and filed separately with the Securities & Exchange Commission.
|----- | ---------------------------------------------------------------------------------------------



3