Exhibit 15(b) UniSource Energy Corporation Tucson Electric Power Company 220 West Sixth Street Tucson, Arizona 85701 We have made a review, in accordance with standards established by the American Institute of Certified Public Accountants, of the unaudited interim financial information of UniSource Energy Corporation and subsidiaries (the Company) and Tucson Electric Power Company and subsidiaries (TEP) for the period ended March 31, 1997 as indicated in our report dated February 23, 1998; because we did not perform an audit, we expressed no opinion on that information. We are aware that our report referred to above, which was included in your Quarterly Reports on Form 10-Q for the quarter ended March 31, 1998 is incorporated by reference in Post-Effective Amendment No. 1 to Registration Statement No. 33- 55732 of TEP on Form S-3, Registration Statement No. 333- 43765, No. 333-43767 and No. 333-43769 of the Company on Form S-8. We are also aware that the aforementioned report, pursuant to Rule 436(c) under the Securities Act of 1933, is not considered a part of the Registration Statement prepared or certified by an accountant or a report prepared or certified by an accountant within the meaning of Sections 7 and 11 of that Act. DELOITTE & TOUCHE LLP Tucson, Arizona May 12, 1998