EXHIBIT 23(c)

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 27, 2009 relating to the consolidated financial statements of Avista Corporation and subsidiaries (the “Company”) (which report expresses an unqualified opinion and includes an explanatory paragraph for certain changes in accounting and presentation resulting from the impact of recently adopted accounting standards) and the effectiveness of the Company’s internal control over financial reporting, appearing in the Annual Report on Form 10-K of Avista Corporation for the year ended December 31, 2008, and to the reference to us under the heading “Experts” in the Prospectus, which is part of this Registration Statement.

/s/ Deloitte & Touche LLP  

Seattle, Washington
December 9, 2009