Exhibit 21

UniSource Energy Corporation Subsidiaries
Subsidiary	State or Other Jurisdiction of Incorporation or Organization
Tucson Electric Power Company (TEP)	Arizona
TEP Subsidiaries:
San Carlos Resources Inc.	Arizona
UniSource Energy Services, Inc. (UES)	Arizona
UES Subsidiaries:
UNS Electric, Inc.	Arizona
UNS Gas, Inc.	Arizona
Millennium Energy Holdings, Inc. (Millennium)	Arizona
Millennium Subsidiaries:
Advanced Energy Technologies, Inc.	Arizona
Global Solar Energy, Inc.	Arizona