Common use of ADDENDUM Clause in Contracts

ADDENDUM. The undersigned Lender (i) agrees to all of the provisions of the Credit Agreement, dated as of April 21, 2005 (the “Credit Agreement”), among Public Service Company of Colorado (the “Borrower”), the Lenders party thereto, the Documentation Agents and Syndication Agents named therein and JPMorgan Chase Bank, N.A., as Administrative Agent, and (ii) becomes a party thereto, as a Lender, with obligations applicable to such Lender thereunder, including, without limitation, the obligation to make extensions of credit to the Borrower in an aggregate principal amount not to exceed the amount of its Revolving Commitment as set forth opposite the undersigned Lender’s name in Schedule 1.1A to the Credit Agreement, as such amount may be changed from time to time as provided in the Credit Agreement. Unless otherwise defined herein, terms defined in the Credit Agreement and used herein shall have the meanings given to them in the Credit Agreement. Amarillo National Bank. By: /s/ ▇▇▇▇▇ ▇. ▇▇▇▇▇▇▇ Name: ▇▇▇▇▇ ▇. ▇▇▇▇▇▇▇ Title: Executive Vice President Dated as of April 21, 2005

ADDENDUM. The undersigned Lender (i) agrees to all of the provisions of the Credit Agreement, dated as of April 21, 2005 (the “Credit Agreement”), among Public Service Company of Colorado (the “Borrower”), the Lenders party thereto, the Documentation Agents and Syndication Agents named therein and JPMorgan Chase Bank, N.A., as Administrative Agent, and (ii) becomes a party thereto, as a Lender, with obligations applicable to such Lender thereunder, including, without limitation, the obligation to make extensions of credit to the Borrower in an aggregate principal amount not to exceed the amount of its Revolving Commitment as set forth opposite the undersigned Lender’s name in Schedule 1.1A to the Credit Agreement, as such amount may be changed from time to time as provided in the Credit Agreement. Unless otherwise defined herein, terms defined in the Credit Agreement and used herein shall have the meanings given to them in the Credit Agreement. Amarillo HSBC Bank USA, National Bank. Association By: /s/ ▇▇▇▇▇ ▇. ▇▇▇▇▇▇▇ Aldeanueva Name: ▇▇▇▇▇ ▇. ▇▇▇▇▇▇▇ Aldeanueva Title: Executive Vice President Dated as of April 2119, 2005

ADDENDUM. The undersigned Lender (i) agrees to all of the provisions of the Credit Agreement, dated as of April 21, 2005 (the “Credit Agreement”), among Southwestern Public Service Company of Colorado (the “Borrower”), the Lenders party thereto, the Documentation Agents and Syndication Agents named therein and JPMorgan Chase Bank, N.A., as Administrative Agent, and (ii) becomes a party thereto, as a Lender, with obligations applicable to such Lender thereunder, including, without limitation, the obligation to make extensions of credit to the Borrower in an aggregate principal amount not to exceed the amount of its Revolving Commitment as set forth opposite the undersigned Lender’s name in Schedule 1.1A to the Credit Agreement, as such amount may be changed from time to time as provided in the Credit Agreement. Unless otherwise defined herein, terms defined in the Credit Agreement and used herein shall have the meanings given to them in the Credit Agreement. Amarillo National Bank. CREDIT SUISSE FIRST BOSTON, ACTING THROUGH ITS CAYMAN ISLANDS BRANCH By: /s/ ▇▇▇▇▇ ▇. ▇ Name: ▇▇▇▇▇ ▇▇ Title: Director By: /s/ ▇▇▇▇▇▇ ▇▇▇▇▇▇▇ Name: ▇▇▇▇▇▇ ▇. ▇▇▇▇▇▇▇ Title: Executive Vice President Associate Dated as of April 2120, 2005

ADDENDUM. The undersigned Lender (i) agrees to all of the provisions of the Credit Agreement, dated as of April 21, 2005 (the “Credit Agreement”), among Public Service Company of Colorado (the “Borrower”), the Lenders party thereto, the Documentation Agents and Syndication Agents named therein and JPMorgan Chase Bank, N.A., as Administrative Agent, and (ii) becomes a party thereto, as a Lender, with obligations applicable to such Lender thereunder, including, without limitation, the obligation to make extensions of credit to the Borrower in an aggregate principal amount not to exceed the amount of its Revolving Commitment as set forth opposite the undersigned Lender’s name in Schedule 1.1A to the Credit Agreement, as such amount may be changed from time to time as provided in the Credit Agreement. Unless otherwise defined herein, terms defined in the Credit Agreement and used herein shall have the meanings given to them in the Credit Agreement. Amarillo National Bank. The Bank of Tokyo-Mitsubishi, Ltd. By: /s/ ▇▇▇▇▇▇▇ ▇. ▇▇▇▇▇▇▇ Name: ▇▇▇▇▇▇▇ ▇. ▇▇▇▇▇▇▇ Title: Executive Vice President VP & Manager Dated as of April 2120, 2005

ADDENDUM. The undersigned Lender (i) agrees to all of the provisions of the Credit Agreement, dated as of April 21, 2005 (the “Credit Agreement”), among Public Service Company of Colorado Northern States Power Company, a Minnesota corporation (the “Borrower”), the Lenders party thereto, the Documentation Agents and Syndication Agents named therein and JPMorgan Chase Bank, N.A., as Administrative Agent, and (ii) becomes a party thereto, as a Lender, with obligations applicable to such Lender thereunder, including, without limitation, the obligation to make extensions of credit to the Borrower in an aggregate principal amount not to exceed the amount of its Revolving Commitment as set forth opposite the undersigned Lender’s name in Schedule 1.1A to the Credit Agreement, as such amount may be changed from time to time as provided in the Credit Agreement. Unless otherwise defined herein, terms defined in the Credit Agreement and used herein shall have the meanings given to them in the Credit Agreement. Amarillo National Bank. ▇▇▇▇▇▇ ▇▇▇▇▇▇▇ Bank By: /s/ ▇▇▇▇▇▇ ▇. ▇▇▇▇▇▇▇ Name: ▇▇▇▇▇▇ ▇. ▇▇▇▇▇▇▇ Title: Executive Vice President ▇▇▇▇▇▇ ▇▇▇▇▇▇▇ Bank Dated as of April 2120, 2005

ADDENDUM. The undersigned Lender (i) agrees to all of the provisions of the Credit Agreement, dated as of April 21, 2005 (the “Credit Agreement”), among Southwestern Public Service Company of Colorado (the “Borrower”), the Lenders party thereto, the Documentation Agents and Syndication Agents named therein and JPMorgan Chase Bank, N.A., as Administrative Agent, and (ii) becomes a party thereto, as a Lender, with obligations applicable to such Lender thereunder, including, without limitation, the obligation to make extensions of credit to the Borrower in an aggregate principal amount not to exceed the amount of its Revolving Commitment as set forth opposite the undersigned Lender’s name in Schedule 1.1A to the Credit Agreement, as such amount may be changed from time to time as provided in the Credit Agreement. Unless otherwise defined herein, terms defined in the Credit Agreement and used herein shall have the meanings given to them in the Credit Agreement. Amarillo National Bank. By: /s/ ▇▇▇▇▇ ▇. ▇▇▇▇▇▇▇ Name: ▇▇▇▇▇ ▇. STREET COMMITMENT CORPORATION (Recourse only to assets of ▇▇▇▇▇▇▇ Street Commitment Corporation) By: /s/ Manda D’Agata Name: Manda D’Agata Title: Executive Assistant Vice President Dated as of April 2119, 2005

ADDENDUM. The undersigned Lender (i) agrees to all of the provisions of the Credit Agreement, dated as of April 21, 2005 (the “Credit Agreement”), among Public Service Company of Colorado Northern States Power Company, a Minnesota corporation (the “Borrower”), the Lenders party thereto, the Documentation Agents and Syndication Agents named therein and JPMorgan Chase Bank, N.A., as Administrative Agent, and (ii) becomes a party thereto, as a Lender, with obligations applicable to such Lender thereunder, including, without limitation, the obligation to make extensions of credit to the Borrower in an aggregate principal amount not to exceed the amount of its Revolving Commitment as set forth opposite the undersigned Lender’s name in Schedule 1.1A to the Credit Agreement, as such amount may be changed from time to time as provided in the Credit Agreement. Unless otherwise defined herein, terms defined in the Credit Agreement and used herein shall have the meanings given to them in the Credit Agreement. Amarillo National Bank. BANK OF AMERICA, N.A. By: /s/ ▇▇▇▇▇▇▇▇ ▇. ▇▇▇▇▇▇▇▇▇▇ Name: ▇▇▇▇▇▇▇▇ ▇. ▇▇▇▇▇▇▇▇▇▇ Title: Executive Senior Vice President Dated as of April 21, 2005

ADDENDUM. The undersigned Lender (i) agrees to all of the provisions of the Credit Agreement, dated as of April 21, 2005 (the “Credit Agreement”), among Public Service Company of Colorado Northern States Power Company, a Minnesota corporation (the “Borrower”), the Lenders party thereto, the Documentation Agents and Syndication Agents named therein and JPMorgan Chase Bank, N.A., as Administrative Agent, and (ii) becomes a party thereto, as a Lender, with obligations applicable to such Lender thereunder, including, without limitation, the obligation to make extensions of credit to the Borrower in an aggregate principal amount not to exceed the amount of its Revolving Commitment as set forth opposite the undersigned Lender’s name in Schedule 1.1A to the Credit Agreement, as such amount may be changed from time to time as provided in the Credit Agreement. Unless otherwise defined herein, terms defined in the Credit Agreement and used herein shall have the meanings given to them in the Credit Agreement. Amarillo National Bank. KEYBANK NATIONAL ASSOCIATION By: /s/ ▇▇▇▇▇ ▇. ▇▇▇▇▇▇▇ Name: ▇▇▇▇▇ ▇. ▇▇▇▇▇▇▇ Title: Executive Vice President Dated as of April 21, 2005

ADDENDUM. The undersigned Lender (i) agrees to all of the provisions of the Credit Agreement, dated as of April 21, 2005 (the “Credit Agreement”), among Public Service Company of Colorado (the “Borrower”), the Lenders party thereto, the Documentation Agents and Syndication Agents named therein and JPMorgan Chase Bank, N.A., as Administrative Agent, and (ii) becomes a party thereto, as a Lender, with obligations applicable to such Lender thereunder, including, without limitation, the obligation to make extensions of credit to the Borrower in an aggregate principal amount not to exceed the amount of its Revolving Commitment as set forth opposite the undersigned Lender’s name in Schedule 1.1A to the Credit Agreement, as such amount may be changed from time to time as provided in the Credit Agreement. Unless otherwise defined herein, terms defined in the Credit Agreement and used herein shall have the meanings given to them in the Credit Agreement. Amarillo National Bank. Mizuho Corporate Bank Ltd. By: /s/ ▇▇▇▇▇ ▇. ▇▇▇▇▇▇▇ Name: ▇▇▇▇▇ ▇. ▇▇▇▇▇▇▇ Title: Executive Senior Vice President Dated as of April 2120, 2005

ADDENDUM. The undersigned Lender (i) agrees to all of the provisions of the Credit Agreement, dated as of April 21, 2005 (the “Credit Agreement”), among Public Service Company of Colorado Northern States Power Company, a Minnesota corporation (the “Borrower”), the Lenders party thereto, the Documentation Agents and Syndication Agents named therein and JPMorgan Chase Bank, N.A., as Administrative Agent, and (ii) becomes a party thereto, as a Lender, with obligations applicable to such Lender thereunder, including, without limitation, the obligation to make extensions of credit to the Borrower in an aggregate principal amount not to exceed the amount of its Revolving Commitment as set forth opposite the undersigned Lender’s name in Schedule 1.1A to the Credit Agreement, as such amount may be changed from time to time as provided in the Credit Agreement. Unless otherwise defined herein, terms defined in the Credit Agreement and used herein shall have the meanings given to them in the Credit Agreement. Amarillo National Bank. BNP Paribas By: /s/ ▇▇▇▇▇▇▇ ▇. ▇▇▇▇▇▇▇ Name: ▇▇▇▇▇▇▇ ▇. ▇▇▇▇▇▇▇ Title: Executive Vice President Managing Director By: /s/ ▇▇▇▇▇ ▇▇▇▇▇▇▇ Name: ▇▇▇▇▇ ▇▇▇▇▇▇▇ Title: Managing Director Dated as of April 21, 2005

ADDENDUM. The undersigned Lender (i) agrees to all of the provisions of the Credit Agreement, dated as of April 21, 2005 (the “Credit Agreement”), among Southwestern Public Service Company of Colorado (the “Borrower”), the Lenders party thereto, the Documentation Agents and Syndication Agents named therein and JPMorgan Chase Bank, N.A., as Administrative Agent, and (ii) becomes a party thereto, as a Lender, with obligations applicable to such Lender thereunder, including, without limitation, the obligation to make extensions of credit to the Borrower in an aggregate principal amount not to exceed the amount of its Revolving Commitment as set forth opposite the undersigned Lender’s name in Schedule 1.1A to the Credit Agreement, as such amount may be changed from time to time as provided in the Credit Agreement. Unless otherwise defined herein, terms defined in the Credit Agreement and used herein shall have the meanings given to them in the Credit Agreement. Amarillo National Bank. Citibank, N.A. By: /s/ ▇▇▇▇▇ ▇. ▇▇▇ ▇▇▇▇▇ Name: ▇▇▇▇▇ ▇. ▇▇▇ ▇▇▇▇▇ Title: Executive Vice President Dated as of April 2119, 2005

ADDENDUM. The undersigned Lender (i) agrees to all of the provisions of the Credit Agreement, dated as of April 21, 2005 (the “Credit Agreement”), among Southwestern Public Service Company of Colorado (the “Borrower”), the Lenders party thereto, the Documentation Agents and Syndication Agents named therein and JPMorgan Chase Bank, N.A., as Administrative Agent, and (ii) becomes a party thereto, as a Lender, with obligations applicable to such Lender thereunder, including, without limitation, the obligation to make extensions of credit to the Borrower in an aggregate principal amount not to exceed the amount of its Revolving Commitment as set forth opposite the undersigned Lender’s name in Schedule 1.1A to the Credit Agreement, as such amount may be changed from time to time as provided in the Credit Agreement. Unless otherwise defined herein, terms defined in the Credit Agreement and used herein shall have the meanings given to them in the Credit Agreement. Amarillo National Bank. KEYBANK NATIONAL ASSOCIATION By: /s/ ▇▇▇▇▇ ▇. ▇▇▇▇▇▇▇ Name: ▇▇▇▇▇ ▇. ▇▇▇▇▇▇▇ Title: Executive Vice President Dated as of April 21, 2005

ADDENDUM. The undersigned Lender (i) agrees to all of the provisions of the Credit Agreement, dated as of April 21, 2005 (the “Credit Agreement”), among Public Service Company of Colorado (the “Borrower”), the Lenders party thereto, the Documentation Agents and Syndication Agents named therein and JPMorgan Chase Bank, N.A., as Administrative Agent, and (ii) becomes a party thereto, as a Lender, with obligations applicable to such Lender thereunder, including, without limitation, the obligation to make extensions of credit to the Borrower in an aggregate principal amount not to exceed the amount of its Revolving Commitment as set forth opposite the undersigned Lender’s name in Schedule 1.1A to the Credit Agreement, as such amount may be changed from time to time as provided in the Credit Agreement. Unless otherwise defined herein, terms defined in the Credit Agreement and used herein shall have the meanings given to them in the Credit Agreement. Amarillo National Bank. BNP Paribas By: /s/ ▇▇▇▇▇▇▇ ▇. ▇▇▇▇▇▇▇ Name: ▇▇▇▇▇▇▇ ▇. ▇▇▇▇▇▇▇ Title: Executive Vice President Managing Director By: /s/ ▇▇▇▇▇ ▇▇▇▇▇▇▇ Name: ▇▇▇▇▇ ▇▇▇▇▇▇▇ Title: Managing Director Dated as of April 21, 2005

ADDENDUM. The undersigned Lender (i) agrees to all of the provisions of the Credit Agreement, dated as of April 21, 2005 (the “Credit Agreement”), among Public Service Company of Colorado (the “Borrower”), the Lenders party thereto, the Documentation Agents and Syndication Agents named therein and JPMorgan Chase Bank, N.A., as Administrative Agent, and (ii) becomes a party thereto, as a Lender, with obligations applicable to such Lender thereunder, including, without limitation, the obligation to make extensions of credit to the Borrower in an aggregate principal amount not to exceed the amount of its Revolving Commitment as set forth opposite the undersigned Lender’s name in Schedule 1.1A to the Credit Agreement, as such amount may be changed from time to time as provided in the Credit Agreement. Unless otherwise defined herein, terms defined in the Credit Agreement and used herein shall have the meanings given to them in the Credit Agreement. Amarillo National Bank. BARCLAYS BANK PLC By: /s/ ▇▇▇▇▇ Sydney ▇. ▇▇▇▇▇▇▇ Name: ▇▇▇▇▇ Sydney ▇. ▇▇▇▇▇▇▇ Title: Executive Vice President Director Dated as of April 21, 2005

ADDENDUM. The undersigned Lender (i) agrees to all of the provisions of the Credit Agreement, dated as of April 21, 2005 (the “Credit Agreement”), among Public Service Company of Colorado (the “Borrower”), the Lenders party thereto, the Documentation Agents and Syndication Agents named therein and JPMorgan Chase Bank, N.A., as Administrative Agent, and (ii) becomes a party thereto, as a Lender, with obligations applicable to such Lender thereunder, including, without limitation, the obligation to make extensions of credit to the Borrower in an aggregate principal amount not to exceed the amount of its Revolving Commitment as set forth opposite the undersigned Lender’s name in Schedule 1.1A to the Credit Agreement, as such amount may be changed from time to time as provided in the Credit Agreement. Unless otherwise defined herein, terms defined in the Credit Agreement and used herein shall have the meanings given to them in the Credit Agreement. Amarillo National Bank. By: /s/ ▇▇▇▇▇▇ ▇▇▇▇▇▇▇ Financing, Inc. By: /s/ Cahal ▇. ▇▇▇▇▇▇▇ Name: ▇▇▇▇▇ Cahal ▇. ▇▇▇▇▇▇▇ Title: Executive Vice President Dated as of April 21, 2005

ADDENDUM. The undersigned Lender (i) agrees to all of the provisions of the Credit Agreement, dated as of April 21, 2005 (the “Credit Agreement”), among Southwestern Public Service Company of Colorado (the “Borrower”), the Lenders party thereto, the Documentation Agents and Syndication Agents named therein and JPMorgan Chase Bank, N.A., as Administrative Agent, and (ii) becomes a party thereto, as a Lender, with obligations applicable to such Lender thereunder, including, without limitation, the obligation to make extensions of credit to the Borrower in an aggregate principal amount not to exceed the amount of its Revolving Commitment as set forth opposite the undersigned Lender’s name in Schedule 1.1A to the Credit Agreement, as such amount may be changed from time to time as provided in the Credit Agreement. Unless otherwise defined herein, terms defined in the Credit Agreement and used herein shall have the meanings given to them in the Credit Agreement. Amarillo HSBC Bank USA, National Bank. Association By: /s/ ▇▇▇▇▇ ▇. ▇▇▇▇▇▇▇ Aldeanueva Name: ▇▇▇▇▇ ▇. ▇▇▇▇▇▇▇ Aldeanueva Title: Executive Vice President Dated as of April 2119, 2005

ADDENDUM. The undersigned Lender (i) agrees to all of the provisions of the Credit Agreement, dated as of April 21, 2005 (the “Credit Agreement”), among Public Service Company of Colorado (the “Borrower”), the Lenders party thereto, the Documentation Agents and Syndication Agents named therein and JPMorgan Chase Bank, N.A., as Administrative Agent, and (ii) becomes a party thereto, as a Lender, with obligations applicable to such Lender thereunder, including, without limitation, the obligation to make extensions of credit to the Borrower in an aggregate principal amount not to exceed the amount of its Revolving Commitment as set forth opposite the undersigned Lender’s name in Schedule 1.1A to the Credit Agreement, as such amount may be changed from time to time as provided in the Credit Agreement. Unless otherwise defined herein, terms defined in the Credit Agreement and used herein shall have the meanings given to them in the Credit Agreement. Amarillo National Bank. ▇▇▇▇▇▇ ▇▇▇▇▇▇▇ Bank By: /s/ ▇▇▇▇▇▇ ▇. ▇▇▇▇▇▇▇ Name: ▇▇▇▇▇▇ ▇. ▇▇▇▇▇▇▇ Title: Executive Vice President ▇▇▇▇▇▇ ▇▇▇▇▇▇▇ Bank Dated as of April 2120, 2005

ADDENDUM. The undersigned Lender (i) agrees to all of the provisions of the Credit Agreement, dated as of April 21, 2005 (the “Credit Agreement”), among Public Service Company of Colorado Northern States Power Company, a Minnesota corporation (the “Borrower”), the Lenders party thereto, the Documentation Agents and Syndication Agents named therein and JPMorgan Chase Bank, N.A., as Administrative Agent, and (ii) becomes a party thereto, as a Lender, with obligations applicable to such Lender thereunder, including, without limitation, the obligation to make extensions of credit to the Borrower in an aggregate principal amount not to exceed the amount of its Revolving Commitment as set forth opposite the undersigned Lender’s name in Schedule 1.1A to the Credit Agreement, as such amount may be changed from time to time as provided in the Credit Agreement. Unless otherwise defined herein, terms defined in the Credit Agreement and used herein shall have the meanings given to them in the Credit Agreement. Amarillo National Bank. ▇▇▇▇▇▇ BROTHERS BANK, FSB By: /s/ ▇▇▇▇▇ ▇. ▇▇▇▇▇▇▇ Name: ▇▇▇▇▇ ▇. ▇▇▇▇▇▇▇ Title: Executive Senior Vice President Dated as of April 21, 2005

ADDENDUM. The undersigned Lender (i) agrees to all of the provisions of the Credit Agreement, dated as of April 21, 2005 (the “Credit Agreement”), among Southwestern Public Service Company of Colorado (the “Borrower”), the Lenders party thereto, the Documentation Agents and Syndication Agents named therein and JPMorgan Chase Bank, N.A., as Administrative Agent, and (ii) becomes a party thereto, as a Lender, with obligations applicable to such Lender thereunder, including, without limitation, the obligation to make extensions of credit to the Borrower in an aggregate principal amount not to exceed the amount of its Revolving Commitment as set forth opposite the undersigned Lender’s name in Schedule 1.1A to the Credit Agreement, as such amount may be changed from time to time as provided in the Credit Agreement. Unless otherwise defined herein, terms defined in the Credit Agreement and used herein shall have the meanings given to them in the Credit Agreement. Amarillo National Bank. BNP Paribas By: /s/ ▇▇▇▇▇▇▇ ▇. ▇▇▇▇▇▇▇ Name: ▇▇▇▇▇▇▇ ▇. ▇▇▇▇▇▇▇ Title: Executive Vice President Managing Director By: /s/ ▇▇▇▇▇ ▇▇▇▇▇▇▇ Name: ▇▇▇▇▇ ▇▇▇▇▇▇▇ Title: Managing Director Dated as of April 21, 2005

ADDENDUM. The undersigned Lender (i) agrees to all of the provisions of the Credit Agreement, dated as of April 21, 2005 (the “Credit Agreement”), among Public Service Company of Colorado Northern States Power Company, a Minnesota corporation (the “Borrower”), the Lenders party thereto, the Documentation Agents and Syndication Agents named therein and JPMorgan Chase Bank, N.A., as Administrative Agent, and (ii) becomes a party thereto, as a Lender, with obligations applicable to such Lender thereunder, including, without limitation, the obligation to make extensions of credit to the Borrower in an aggregate principal amount not to exceed the amount of its Revolving Commitment as set forth opposite the undersigned Lender’s name in Schedule 1.1A to the Credit Agreement, as such amount may be changed from time to time as provided in the Credit Agreement. Unless otherwise defined herein, terms defined in the Credit Agreement and used herein shall have the meanings given to them in the Credit Agreement. Amarillo National Bank. BARCLAYS BANK PLC By: /s/ ▇▇▇▇▇ Sydney ▇. ▇▇▇▇▇▇▇ Name: ▇▇▇▇▇ Sydney ▇. ▇▇▇▇▇▇▇ Title: Executive Vice President Director Dated as of April 21, 2005

ADDENDUM. The undersigned Lender (i) agrees to all of the provisions of the Credit Agreement, dated as of April 21, 2005 (the “Credit Agreement”), among Public Service Company of Colorado (the “Borrower”), the Lenders party thereto, the Documentation Agents and Syndication Agents named therein and JPMorgan Chase Bank, N.A., as Administrative Agent, and (ii) becomes a party thereto, as a Lender, with obligations applicable to such Lender thereunder, including, without limitation, the obligation to make extensions of credit to the Borrower in an aggregate principal amount not to exceed the amount of its Revolving Commitment as set forth opposite the undersigned Lender’s name in Schedule 1.1A to the Credit Agreement, as such amount may be changed from time to time as provided in the Credit Agreement. Unless otherwise defined herein, terms defined in the Credit Agreement and used herein shall have the meanings given to them in the Credit Agreement. Amarillo National Bank. ▇▇▇▇▇▇▇ ▇▇▇▇▇ BANK USA By: /s/ ▇▇▇▇▇ ▇. ▇▇▇▇▇▇▇ Name: ▇▇▇▇▇ ▇. ▇▇▇▇▇▇▇ Title: Executive Vice President Director Dated as of April 21, 2005

ADDENDUM. The undersigned Lender (i) agrees to all of the provisions of the Credit Agreement, dated as of April 21, 2005 (the “Credit Agreement”), among Southwestern Public Service Company of Colorado (the “Borrower”), the Lenders party thereto, the Documentation Agents and Syndication Agents named therein and JPMorgan Chase Bank, N.A., as Administrative Agent, and (ii) becomes a party thereto, as a Lender, with obligations applicable to such Lender thereunder, including, without limitation, the obligation to make extensions of credit to the Borrower in an aggregate principal amount not to exceed the amount of its Revolving Commitment as set forth opposite the undersigned Lender’s name in Schedule 1.1A to the Credit Agreement, as such amount may be changed from time to time as provided in the Credit Agreement. Unless otherwise defined herein, terms defined in the Credit Agreement and used herein shall have the meanings given to them in the Credit Agreement. Amarillo National Bank. The Bank of Tokyo-Mitsubishi, Ltd By: /s/ ▇▇▇▇▇▇▇ ▇. ▇▇▇▇▇▇▇ Name: ▇▇▇▇▇▇▇ ▇. ▇▇▇▇▇▇▇ Title: Executive Vice President VP & Manager Dated as of April 2120, 2005

ADDENDUM. The undersigned Lender (i) agrees to all of the provisions of the Credit Agreement, dated as of April 21, 2005 (the “Credit Agreement”), among Public Service Company of Colorado Northern States Power Company, a Minnesota corporation (the “Borrower”), the Lenders party thereto, the Documentation Agents and Syndication Agents named therein and JPMorgan Chase Bank, N.A., as Administrative Agent, and (ii) becomes a party thereto, as a Lender, with obligations applicable to such Lender thereunder, including, without limitation, the obligation to make extensions of credit to the Borrower in an aggregate principal amount not to exceed the amount of its Revolving Commitment as set forth opposite the undersigned Lender’s name in Schedule 1.1A to the Credit Agreement, as such amount may be changed from time to time as provided in the Credit Agreement. Unless otherwise defined herein, terms defined in the Credit Agreement and used herein shall have the meanings given to them in the Credit Agreement. Amarillo HSBC Bank USA, National Bank. Association By: /s/ ▇▇▇▇▇ ▇. ▇▇▇▇▇▇▇ Aldeanueva Name: ▇▇▇▇▇ ▇. ▇▇▇▇▇▇▇ Aldeanueva Title: Executive Vice President Dated as of April 2119, 2005

ADDENDUM. The undersigned Lender (i) agrees to all of the provisions of the Credit Agreement, dated as of April 21, 2005 (the “Credit Agreement”), among Southwestern Public Service Company of Colorado (the “Borrower”), the Lenders party thereto, the Documentation Agents and Syndication Agents named therein and JPMorgan Chase Bank, N.A., as Administrative Agent, and (ii) becomes a party thereto, as a Lender, with obligations applicable to such Lender thereunder, including, without limitation, the obligation to make extensions of credit to the Borrower in an aggregate principal amount not to exceed the amount of its Revolving Commitment as set forth opposite the undersigned Lender’s name in Schedule 1.1A to the Credit Agreement, as such amount may be changed from time to time as provided in the Credit Agreement. Unless otherwise defined herein, terms defined in the Credit Agreement and used herein shall have the meanings given to them in the Credit Agreement. Amarillo National Bank. SUMITOMO MITSUI BANKING CORPORATION By: /s/ ▇▇▇▇▇ ▇. ▇▇▇▇▇▇▇ Name: ▇▇▇▇▇ ▇. ▇▇▇▇▇▇▇ Title: Executive Senior Vice President Dated as of April 2119, 2005

ADDENDUM. The undersigned Lender (i) agrees to all of the provisions of the Credit Agreement, dated as of April 21, 2005 (the “Credit Agreement”), among Public Service Company of Colorado Northern States Power Company, a Minnesota corporation (the “Borrower”), the Lenders party thereto, the Documentation Agents and Syndication Agents named therein and JPMorgan Chase Bank, N.A., as Administrative Agent, and (ii) becomes a party thereto, as a Lender, with obligations applicable to such Lender thereunder, including, without limitation, the obligation to make extensions of credit to the Borrower in an aggregate principal amount not to exceed the amount of its Revolving Commitment as set forth opposite the undersigned Lender’s name in Schedule 1.1A to the Credit Agreement, as such amount may be changed from time to time as provided in the Credit Agreement. Unless otherwise defined herein, terms defined in the Credit Agreement and used herein shall have the meanings given to them in the Credit Agreement. Amarillo National Bank. By: /s/ ▇▇▇▇▇ ▇. ▇▇▇▇▇▇▇ Name: ▇▇▇▇▇ ▇. STREET COMMITMENT CORPORATION (Recourse only to assets of ▇▇▇▇▇▇▇ Street Commitment Corporation) By: /s/ Manda D’Agata Name: Manda D’Agata Title: Executive Assistant Vice President Dated as of April 2119, 2005

ADDENDUM. The undersigned Lender (i) agrees to all of the provisions of the Credit Agreement, dated as of April 21, 2005 (the “Credit Agreement”), among Southwestern Public Service Company of Colorado (the “Borrower”), the Lenders party thereto, the Documentation Agents and Syndication Agents named therein and JPMorgan Chase Bank, N.A., as Administrative Agent, and (ii) becomes a party thereto, as a Lender, with obligations applicable to such Lender thereunder, including, without limitation, the obligation to make extensions of credit to the Borrower in an aggregate principal amount not to exceed the amount of its Revolving Commitment as set forth opposite the undersigned Lender’s name in Schedule 1.1A to the Credit Agreement, as such amount may be changed from time to time as provided in the Credit Agreement. Unless otherwise defined herein, terms defined in the Credit Agreement and used herein shall have the meanings given to them in the Credit Agreement. Amarillo National Bank. BANK OF AMERICA, N.A. By: /s/ ▇▇▇▇▇▇▇▇ ▇. ▇▇▇▇▇▇▇▇▇▇ Name: ▇▇▇▇▇▇▇▇ ▇. ▇▇▇▇▇▇▇▇▇▇ Title: Executive Senior Vice President Dated as of April 21, 2005

ADDENDUM. The undersigned Lender (i) agrees to all of the provisions of the Credit Agreement, dated as of April 21, 2005 (the “Credit Agreement”), among Public Service Company of Colorado Northern States Power Company, a Minnesota corporation (the “Borrower”), the Lenders party thereto, the Documentation Agents and Syndication Agents named therein and JPMorgan Chase Bank, N.A., as Administrative Agent, and (ii) becomes a party thereto, as a Lender, with obligations applicable to such Lender thereunder, including, without limitation, the obligation to make extensions of credit to the Borrower in an aggregate principal amount not to exceed the amount of its Revolving Commitment as set forth opposite the undersigned Lender’s name in Schedule 1.1A to the Credit Agreement, as such amount may be changed from time to time as provided in the Credit Agreement. Unless otherwise defined herein, terms defined in the Credit Agreement and used herein shall have the meanings given to them in the Credit Agreement. Amarillo National Bank. Mizuho Corporate Bank Ltd. By: /s/ ▇▇▇▇▇ ▇. ▇▇▇▇▇▇▇ Name: ▇▇▇▇▇ ▇. ▇▇▇▇▇▇▇ Title: Executive Senior Vice President Dated as of April 2120, 2005

ADDENDUM. The undersigned Lender (i) agrees to all of the provisions of the Credit Agreement, dated as of April 21, 2005 (the “Credit Agreement”), among Southwestern Public Service Company of Colorado (the “Borrower”), the Lenders party thereto, the Documentation Agents and Syndication Agents named therein and JPMorgan Chase Bank, N.A., as Administrative Agent, and (ii) becomes a party thereto, as a Lender, with obligations applicable to such Lender thereunder, including, without limitation, the obligation to make extensions of credit to the Borrower in an aggregate principal amount not to exceed the amount of its Revolving Commitment as set forth opposite the undersigned Lender’s name in Schedule 1.1A to the Credit Agreement, as such amount may be changed from time to time as provided in the Credit Agreement. Unless otherwise defined herein, terms defined in the Credit Agreement and used herein shall have the meanings given to them in the Credit Agreement. Amarillo National Bank. KBC BANK N.V. By: /s/ ▇▇▇▇ ▇▇▇▇▇▇ Name: ▇▇▇▇ ▇▇▇▇▇▇ Title: Vice President By: /s/ ▇▇▇▇▇▇ ▇. ▇▇▇▇▇▇▇ Name: ▇▇▇▇▇▇ ▇. ▇▇▇▇▇▇▇ Title: Executive First Vice President Dated as of April 2119, 2005

ADDENDUM. The undersigned Lender (i) agrees to all of the provisions of the Credit Agreement, dated as of April 21, 2005 (the “Credit Agreement”), among Southwestern Public Service Company of Colorado (the “Borrower”), the Lenders party thereto, the Documentation Agents and Syndication Agents named therein and JPMorgan Chase Bank, N.A., as Administrative Agent, and (ii) becomes a party thereto, as a Lender, with obligations applicable to such Lender thereunder, including, without limitation, the obligation to make extensions of credit to the Borrower in an aggregate principal amount not to exceed the amount of its Revolving Commitment as set forth opposite the undersigned Lender’s name in Schedule 1.1A to the Credit Agreement, as such amount may be changed from time to time as provided in the Credit Agreement. Unless otherwise defined herein, terms defined in the Credit Agreement and used herein shall have the meanings given to them in the Credit Agreement. Amarillo National Bank. ▇▇▇▇▇▇ BROTHERS BANK, FSB By: /s/ ▇▇▇▇▇ ▇. ▇▇▇▇▇▇▇ Name: ▇▇▇▇▇ ▇. ▇▇▇▇▇▇▇ Title: Executive Senior Vice President Dated as of April 21, 2005

ADDENDUM. The undersigned Lender (i) agrees to all of the provisions of the Credit Agreement, dated as of April 21, 2005 (the “Credit Agreement”), among Public Service Company of Colorado (the “Borrower”), the Lenders party thereto, the Documentation Agents and Syndication Agents named therein and JPMorgan Chase Bank, N.A., as Administrative Agent, and (ii) becomes a party thereto, as a Lender, with obligations applicable to such Lender thereunder, including, without limitation, the obligation to make extensions of credit to the Borrower in an aggregate principal amount not to exceed the amount of its Revolving Commitment as set forth opposite the undersigned Lender’s name in Schedule 1.1A to the Credit Agreement, as such amount may be changed from time to time as provided in the Credit Agreement. Unless otherwise defined herein, terms defined in the Credit Agreement and used herein shall have the meanings given to them in the Credit Agreement. Amarillo National Bank. CREDIT SUISSE FIRST BOSTON, ACTING THROUGH ITS CAYMAN ISLANDS BRANCH By: /s/ ▇▇▇▇▇ ▇. ▇ Name: ▇▇▇▇▇ ▇▇ Title: Director By: /s/ ▇▇▇▇▇▇ ▇▇▇▇▇▇▇ Name: ▇▇▇▇▇▇ ▇. ▇▇▇▇▇▇▇ Title: Executive Vice President Associate Dated as of April 2120, 2005

ADDENDUM. The undersigned Lender (i) agrees to all of the provisions of the Credit Agreement, dated as of April 21, 2005 (the “Credit Agreement”), among Southwestern Public Service Company of Colorado (the “Borrower”), the Lenders party thereto, the Documentation Agents and Syndication Agents named therein and JPMorgan Chase Bank, N.A., as Administrative Agent, and (ii) becomes a party thereto, as a Lender, with obligations applicable to such Lender thereunder, including, without limitation, the obligation to make extensions of credit to the Borrower in an aggregate principal amount not to exceed the amount of its Revolving Commitment as set forth opposite the undersigned Lender’s name in Schedule 1.1A to the Credit Agreement, as such amount may be changed from time to time as provided in the Credit Agreement. Unless otherwise defined herein, terms defined in the Credit Agreement and used herein shall have the meanings given to them in the Credit Agreement. Amarillo National Bank. ▇▇▇▇▇▇ ▇▇▇▇▇▇▇ Bank By: /s/ ▇▇▇▇▇▇ ▇. ▇▇▇▇▇▇▇ Name: ▇▇▇▇▇▇ ▇. ▇▇▇▇▇▇▇ Title: Executive Vice President Dated as of April 2120, 2005

ADDENDUM. The undersigned Lender (i) agrees to all of the provisions of the Credit Agreement, dated as of April 21, 2005 (the “Credit Agreement”), among Southwestern Public Service Company of Colorado (the “Borrower”), the Lenders party thereto, the Documentation Agents and Syndication Agents named therein and JPMorgan Chase Bank, N.A., as Administrative Agent, and (ii) becomes a party thereto, as a Lender, with obligations applicable to such Lender thereunder, including, without limitation, the obligation to make extensions of credit to the Borrower in an aggregate principal amount not to exceed the amount of its Revolving Commitment as set forth opposite the undersigned Lender’s name in Schedule 1.1A to the Credit Agreement, as such amount may be changed from time to time as provided in the Credit Agreement. Unless otherwise defined herein, terms defined in the Credit Agreement and used herein shall have the meanings given to them in the Credit Agreement. Amarillo National Bank. By: /s/ ▇▇▇▇▇ ▇. ▇▇▇▇▇▇▇ Name: ▇▇▇▇▇ ▇. ▇▇▇▇▇▇▇ Title: Executive Vice President Dated as of April 21, 2005.

ADDENDUM. The undersigned Lender (i) agrees to all of the provisions of the Credit Agreement, dated as of April 21, 2005 (the “Credit Agreement”), among Public Service Company of Colorado Northern States Power Company, a Minnesota corporation (the “Borrower”), the Lenders party thereto, the Documentation Agents and Syndication Agents named therein and JPMorgan Chase Bank, N.A., as Administrative Agent, and (ii) becomes a party thereto, as a Lender, with obligations applicable to such Lender thereunder, including, without limitation, the obligation to make extensions of credit to the Borrower in an aggregate principal amount not to exceed the amount of its Revolving Commitment as set forth opposite the undersigned Lender’s name in Schedule 1.1A to the Credit Agreement, as such amount may be changed from time to time as provided in the Credit Agreement. Unless otherwise defined herein, terms defined in the Credit Agreement and used herein shall have the meanings given to them in the Credit Agreement. Amarillo National Bank. SUMITOMO MITSUI BANKING CORPORATION By: /s/ ▇▇▇▇▇ ▇. ▇▇▇▇▇▇▇ Name: ▇▇▇▇▇ ▇. ▇▇▇▇▇▇▇ Title: Executive Senior Vice President Dated as of April 2119, 2005

ADDENDUM. The undersigned Lender (i) agrees to all of the provisions of the Credit Agreement, dated as of April 21, 2005 (the “Credit Agreement”), among Southwestern Public Service Company of Colorado (the “Borrower”), the Lenders party thereto, the Documentation Agents and Syndication Agents named therein and JPMorgan Chase Bank, N.A., as Administrative Agent, and (ii) becomes a party thereto, as a Lender, with obligations applicable to such Lender thereunder, including, without limitation, the obligation to make extensions of credit to the Borrower in an aggregate principal amount not to exceed the amount of its Revolving Commitment as set forth opposite the undersigned Lender’s name in Schedule 1.1A to the Credit Agreement, as such amount may be changed from time to time as provided in the Credit Agreement. Unless otherwise defined herein, terms defined in the Credit Agreement and used herein shall have the meanings given to them in the Credit Agreement. Amarillo National Bank. Bank By: /s/ ▇▇▇▇▇ ▇. ▇▇▇▇▇▇▇ Name: ▇▇▇▇▇ ▇. ▇▇▇▇▇▇▇ Title: Executive Vice President Dated as of April 21, 2005

ADDENDUM. The undersigned Lender (i) agrees to all of the provisions of the Credit Agreement, dated as of April 21, 2005 (the “Credit Agreement”), among Public Service Company of Colorado Northern States Power Company, a Minnesota corporation (the “Borrower”), the Lenders party thereto, the Documentation Agents and Syndication Agents named therein and JPMorgan Chase Bank, N.A., as Administrative Agent, and (ii) becomes a party thereto, as a Lender, with obligations applicable to such Lender thereunder, including, without limitation, the obligation to make extensions of credit to the Borrower in an aggregate principal amount not to exceed the amount of its Revolving Commitment as set forth opposite the undersigned Lender’s name in Schedule 1.1A to the Credit Agreement, as such amount may be changed from time to time as provided in the Credit Agreement. Unless otherwise defined herein, terms defined in the Credit Agreement and used herein shall have the meanings given to them in the Credit Agreement. Amarillo National Bank. CREDIT SUISSE FIRST BOSTON, ACTING THROUGH ITS CAYMAN ISLANDS BRANCH By: /s/ ▇▇▇▇▇ ▇. ▇ Name: ▇▇▇▇▇ ▇▇ Title: Director By: /s/ ▇▇▇▇▇▇ ▇▇▇▇▇▇▇ Name: ▇▇▇▇▇▇ ▇. ▇▇▇▇▇▇▇ Title: Executive Vice President Associate Dated as of April 2120, 2005

ADDENDUM. The undersigned Lender (i) agrees to all of the provisions of the Credit Agreement, dated as of April 21, 2005 (the “Credit Agreement”), among Southwestern Public Service Company of Colorado (the “Borrower”), the Lenders party thereto, the Documentation Agents and Syndication Agents named therein and JPMorgan Chase Bank, N.A., as Administrative Agent, and (ii) becomes a party thereto, as a Lender, with obligations applicable to such Lender thereunder, including, without limitation, the obligation to make extensions of credit to the Borrower in an aggregate principal amount not to exceed the amount of its Revolving Commitment as set forth opposite the undersigned Lender’s name in Schedule 1.1A to the Credit Agreement, as such amount may be changed from time to time as provided in the Credit Agreement. Unless otherwise defined herein, terms defined in the Credit Agreement and used herein shall have the meanings given to them in the Credit Agreement. Amarillo National Bank. ▇▇▇▇▇▇▇ ▇▇▇▇▇ BANK USA By: /s/ ▇▇▇▇▇ ▇. ▇▇▇▇▇▇▇ Name: ▇▇▇▇▇ ▇. ▇▇▇▇▇▇▇ Title: Executive Vice President Director Dated as of April 21, 2005

ADDENDUM. The undersigned Lender (i) agrees to all of the provisions of the Credit Agreement, dated as of April 21, 2005 (the “Credit Agreement”), among Public Service Company of Colorado (the “Borrower”), the Lenders party thereto, the Documentation Agents and Syndication Agents named therein and JPMorgan Chase Bank, N.A., as Administrative Agent, and (ii) becomes a party thereto, as a Lender, with obligations applicable to such Lender thereunder, including, without limitation, the obligation to make extensions of credit to the Borrower in an aggregate principal amount not to exceed the amount of its Revolving Commitment as set forth opposite the undersigned Lender’s name in Schedule 1.1A to the Credit Agreement, as such amount may be changed from time to time as provided in the Credit Agreement. Unless otherwise defined herein, terms defined in the Credit Agreement and used herein shall have the meanings given to them in the Credit Agreement. Amarillo National Bank. By: /s/ ▇▇▇▇▇ ▇. ▇▇▇▇▇▇▇ Name: ▇▇▇▇▇ ▇. ▇▇▇▇▇▇▇ Title: Executive Vice President Dated as of April 21, 2005.

ADDENDUM. The undersigned Lender (i) agrees to all of the provisions of the Credit Agreement, dated as of April 21, 2005 (the “Credit Agreement”), among Public Service Company of Colorado Northern States Power Company, a Minnesota corporation (the “Borrower”), the Lenders party thereto, the Documentation Agents and Syndication Agents named therein and JPMorgan Chase Bank, N.A., as Administrative Agent, and (ii) becomes a party thereto, as a Lender, with obligations applicable to such Lender thereunder, including, without limitation, the obligation to make extensions of credit to the Borrower in an aggregate principal amount not to exceed the amount of its Revolving Commitment as set forth opposite the undersigned Lender’s name in Schedule 1.1A to the Credit Agreement, as such amount may be changed from time to time as provided in the Credit Agreement. Unless otherwise defined herein, terms defined in the Credit Agreement and used herein shall have the meanings given to them in the Credit Agreement. Amarillo National Bank. The Bank of Nova Scotia By: /s/ ▇▇▇▇▇ ▇. ▇▇▇▇▇▇▇ Name: ▇▇▇▇▇ ▇. ▇▇▇▇▇▇▇ Title: Executive Vice President Managing Director Dated as of April 2119, 2005

ADDENDUM. The undersigned Lender (i) agrees to all of the provisions of the Credit Agreement, dated as of April 21, 2005 (the “Credit Agreement”), among Southwestern Public Service Company of Colorado (the “Borrower”), the Lenders party thereto, the Documentation Agents and Syndication Agents named therein and JPMorgan Chase Bank, N.A., as Administrative Agent, and (ii) becomes a party thereto, as a Lender, with obligations applicable to such Lender thereunder, including, without limitation, the obligation to make extensions of credit to the Borrower in an aggregate principal amount not to exceed the amount of its Revolving Commitment as set forth opposite the undersigned Lender’s name in Schedule 1.1A to the Credit Agreement, as such amount may be changed from time to time as provided in the Credit Agreement. Unless otherwise defined herein, terms defined in the Credit Agreement and used herein shall have the meanings given to them in the Credit Agreement. Amarillo National Bank. The Bank of Nova Scotia By: /s/ ▇▇▇▇▇ ▇. ▇▇▇▇▇▇▇ Name: ▇▇▇▇▇ ▇. ▇▇▇▇▇▇▇ Title: Executive Vice President Managing Director Dated as of April 2119, 2005

ADDENDUM. The undersigned Lender (i) agrees to all of the provisions of the Credit Agreement, dated as of April 21, 2005 (the “Credit Agreement”), among Public Service Company of Colorado Northern States Power Company, a Minnesota corporation (the “Borrower”), the Lenders party thereto, the Documentation Agents and Syndication Agents named therein and JPMorgan Chase Bank, N.A., as Administrative Agent, and (ii) becomes a party thereto, as a Lender, with obligations applicable to such Lender thereunder, including, without limitation, the obligation to make extensions of credit to the Borrower in an aggregate principal amount not to exceed the amount of its Revolving Commitment as set forth opposite the undersigned Lender’s name in Schedule 1.1A to the Credit Agreement, as such amount may be changed from time to time as provided in the Credit Agreement. Unless otherwise defined herein, terms defined in the Credit Agreement and used herein shall have the meanings given to them in the Credit Agreement. Amarillo National Bank. KBC BANK N.V. By: /s/ ▇▇▇▇ ▇▇▇▇▇▇ Name: ▇▇▇▇ ▇▇▇▇▇▇ Title: Vice President By: /s/ ▇▇▇▇▇▇ ▇. ▇▇▇▇▇▇▇ Name: ▇▇▇▇▇▇ ▇. ▇▇▇▇▇▇▇ Title: Executive First Vice President Dated as of April 2119, 2005

ADDENDUM. The undersigned Lender (i) agrees to all of the provisions of the Credit Agreement, dated as of April 21, 2005 (the “Credit Agreement”), among Southwestern Public Service Company of Colorado (the “Borrower”), the Lenders party thereto, the Documentation Agents and Syndication Agents named therein and JPMorgan Chase Bank, N.A., as Administrative Agent, and (ii) becomes a party thereto, as a Lender, with obligations applicable to such Lender thereunder, including, without limitation, the obligation to make extensions of credit to the Borrower in an aggregate principal amount not to exceed the amount of its Revolving Commitment as set forth opposite the undersigned Lender’s name in Schedule 1.1A to the Credit Agreement, as such amount may be changed from time to time as provided in the Credit Agreement. Unless otherwise defined herein, terms defined in the Credit Agreement and used herein shall have the meanings given to them in the Credit Agreement. Amarillo National Bank. Mizuho Corporate Bank Ltd. By: /s/ ▇▇▇▇▇ ▇. ▇▇▇▇▇▇▇ Name: ▇▇▇▇▇ ▇. ▇▇▇▇▇▇▇ Title: Executive Senior Vice President Dated as of April 2120, 2005

ADDENDUM. The undersigned Lender (i) agrees to all of the provisions of the Credit Agreement, dated as of April 21, 2005 (the “Credit Agreement”), among Public Service Company of Colorado Northern States Power Company, a Minnesota corporation (the “Borrower”), the Lenders party thereto, the Documentation Agents and Syndication Agents named therein and JPMorgan Chase Bank, N.A., as Administrative Agent, and (ii) becomes a party thereto, as a Lender, with obligations applicable to such Lender thereunder, including, without limitation, the obligation to make extensions of credit to the Borrower in an aggregate principal amount not to exceed the amount of its Revolving Commitment as set forth opposite the undersigned Lender’s name in Schedule 1.1A to the Credit Agreement, as such amount may be changed from time to time as provided in the Credit Agreement. Unless otherwise defined herein, terms defined in the Credit Agreement and used herein shall have the meanings given to them in the Credit Agreement. Amarillo National Bank. ▇▇▇▇▇▇▇ ▇▇▇▇▇ BANK USA By: /s/ ▇▇▇▇▇ ▇. ▇▇▇▇▇▇▇ Name: ▇▇▇▇▇ ▇. ▇▇▇▇▇▇▇ Title: Executive Vice President Director Dated as of April 21, 2005