Exhibit 23.03

CONSENT OF INDEPENDENT REGISTERED PUBLIC ACCOUNTING FIRM

We consent to the incorporation by reference in this Registration Statement on Form S-3 of our report dated February 24, 2006, relating to the financial statements and financial statement schedule of Southwestern Public Service Company, appearing in the Annual Report on Form 10-K of Southwestern Public Service Company for the year ended December 31, 2005 and to the reference to us under the heading “Experts” in the Prospectus, which is part of this Registration Statement.

/s/ DELOITTE & TOUCHE LLP

Minneapolis, Minnesota

March 24, 2006