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|   |   |   |   |   |

|   |
|---|
|   |  |
| x | QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 |

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|--------|
|        |  |
| ¨ | TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 |

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|----------------------------------------------------------------|
|                                                                |  |  |
| Colorado                                                       |   | 84-0296600 |
| (State or other jurisdiction of incorporation or organization) |   | (I.R.S. Employer Identification No.) |
|                                                           |   |   |
| 1800 Larimer, Suite 1100                                       |   |   |
| Denver, Colorado                                               |   | 80202 |
| (Address of principal executive offices)                       |   | (Zip Code) |

|                                             |
|---------------------------------------------|
|                                             |  |  |
| Large accelerated filer ¨              |   | Accelerated filer ¨ |
|                                        |   |   |
| Non-accelerated filer x                     |   | Smaller reporting company ¨ |
| (Do not check if smaller reporting company) |   |   |

|                               |
|-------------------------------|
|                               |  |  |
| Class                         |   | Outstanding at Oct. 28, 2013 |
| Common Stock, $0.01 par value |   | 100 shares |

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|        |  |  |  |  |
|   |   |   |   |   |

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|    |  |
| *  | Indicates incorporation by reference |
| #  | This exhibit is filed or furnished herewith |
| ## | This exhibit has been previously filed or furnished |

|         |
|---------|
|         |  |
| ##3.01* | Amended and Restated Articles of Incorporation dated July 15, 1998 (Form 10-K, Dec. 31, 1998, Exhibit 3(a)(1)). |
| #3.02   | By-Laws of PSCo as Amended and Restated on Sept. 26, 2013. |
| #31.01  | Principal Executive Officer’s certifications pursuant to 18 U.S.C. Section 1350, as adopted pursuant to Section 302 of the Sarbanes-Oxley Act of 2002. |
| #31.02  | Principal Financial Officer’s certifications pursuant to 18 U.S.C. Section 1350, as adopted pursuant to Section 302 of the Sarbanes-Oxley Act of 2002. |
| ##32.01 | Certification pursuant to 18 U.S.C. Section 1350, as adopted pursuant to Section 906 of the Sarbanes-Oxley Act of 2002. |
| ##99.01 | Statement pursuant to Private Securities Litigation Reform Act of 1995. |
| ##101   | The following materials from PSCo’s Quarterly Report on Form 10-Q for the quarter ended Sept. 30, 2013 are formatted in XBRL (eXtensible Business Reporting Language):  (i) the Consolidated Statements of Income, (ii) the Consolidated Statements of Comprehensive Income (iii) the Consolidated Statements of Cash Flows, (iv) the Consolidated Balance Sheets, (v) Notes to Condensed Consolidated Financial Statements, and (vi) document and entity information. |

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|              |
|--------------|
|              |  |  |
|         |   | Public Service Company of Colorado |
|         |   |   |
| Nov. 8, 2013 | By: | /s/ JEFFREY S. SAVAGE |
|         |   | Jeffrey S. Savage |
|         |   | Vice President and Controller |
|         |   |   |
|         |   | /s/ TERESA S. MADDEN |
|         |   | Teresa S. Madden |
|         |   | Senior Vice President, Chief Financial Officer and Director |