**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                  June 30,                  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:                  August 7, 2007 |   | /s/                Kevin P.                Larson                                                                                           |
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|                                            |   | Kevin                P.                LarsonChief                  Financial Officer, Senior Vice President and                  Treasurer |