**Exhibit      31(b)**

**CERTIFICATION**

**Pursuant        to        Section 302 of the Sarbanes-Oxley Act**

| 1.                  | I                have                reviewed the quarterly report on Form 10-Q for the quarter ended                March 31,                2007, of UniSource Energy Corporation; |
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| 2.                  | Based                on my                knowledge, this report does not contain any untrue statement of a                material                fact or omit to state a material fact necessary to make the statements                made, in light of the circumstances under which such statements were                made,                not misleading with respect to the period covered by this                report; |
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| 3.                  | Based                on my                knowledge, the financial statements, and other financial information                included in this report, fairly present in all material respects                the                financial condition, results of operations and cash flows of the                registrant as of, and for, the periods presented in this                report; |
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| 4.    | The                registrant’s other certifying officer and I are responsible for                establishing and maintaining disclosure controls and procedures (as                defined in Exchange Act Rules 13a-15(e) and 15d-15(e)) and internal                control over financial reporting (as defined in Exchange Act Rules                13a-15(f) and 15d-15(f)) for the registrant and                have: |
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| a.      | designed                such                disclosure controls and procedures, or caused such disclosure controls                and                procedures to be designed under our supervision, to ensure that material                information relating to the registrant, including its consolidated                subsidiaries, is made known to us by others within those entities,                particularly during the period in which this report is being                prepared; |
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| b.      | designed                such                internal control over financial reporting, or caused such internal                control                over financial reporting to be designed under our supervision, to                provide                reasonable assurance regarding the reliability of financial reporting                and                the preparation of financial statements for external purposes in                accordance with generally accepted accounting                principles; |
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| c.      | evaluated                the                effectiveness of the registrant’s disclosure controls and procedures and                presented in this report our conclusions about the effectiveness                of the                disclosure controls and procedures, as of the end of the period covered                by                this report based on such evaluation; and |
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| d.      | disclosed                in                this report any change in the registrant’s internal control over financial                reporting that occurred during the registrant’s most recent fiscal quarter                (the registrant’s fourth fiscal quarter in the case of an annual report)                that has materially affected, or is reasonably likely to materially                affect, the registrant’s internal control over financial reporting;                and |
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| 5.   | The                registrant’s other certifying officer and I have disclosed, based on our                most recent evaluation of internal control over financial reporting,                to                the registrant’s auditors and the audit committee of the registrant’s                board of directors (or persons performing the equivalent                functions): |
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| a.      | all                significant deficiencies and material weaknesses in the design or                operation of internal control over financial reporting which are                reasonably likely to adversely affect the registrant’s ability to record,                process, summarize and report financial information;                and |
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| b.      | any                fraud,                whether or not material, that involves management or other employees                who                have a significant role in the registrant’s internal control over                financial reporting. |
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| Date: May                8,                2007 | /s/                Kevin P.                Larson                                                                                               |
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|                                                 | Kevin                  P.                  LarsonChief                  Financial Officer, Senior Vice President and                  Treasurer |