Although high temperatures and powerful thunderstorms arrive in the summer, UniSource prepares for them all year long through maintenance and upgrades to the electric systems that serve our communities.

Since the beginning of 2019, we’ve invested more than $78 million to maintain and improve our electric transmission and distribution systems, including substations, poles, power lines, and other equipment that deliver power to customers’ homes and businesses. These improvements are designed to withstand extreme heat, monsoon storms, and increasing peak energy demands.

UniSource employees are hard at work on these improvement projects year-round and throughout our service territories.

“We prepare for summer all year long by making sure our transmission systems, substations, generating resources and distribution facilities are in the best shape possible,” said Roberto Guevara, UniSource Director of Gas, Electric and Operational Excellence. “We also coordinate with emergency responders in advance of any heat-related emergencies or thunderstorms that could impact our service to customers.”


UniSource installed a mobile substation next to our Sonoita Substation in Rio Rico. Peak energy use in that area increased 13 percent last year, driving systemwide usage to a new all-time high. The mobile substation will quickly expand system capacity, allowing for additional growth in the area while supporting reliable service for customers this summer.

Construction of the $4 million project began in March and was scheduled for completion last month. The mobile substation will remain in place as UniSource explores suitable long-term solutions, which could include installation of larger transformers at that location or construction of a new substation. After a long-term solution is in place, the mobile substation will be used in emergencies throughout UniSource’s electric service territories.


UniSource invested about $500,000 to upgrade a line between the South Kingman Substation in central Kingman and the Sunrise Substation near Interstate 40 and Stockton Hill Road. In addition to installing about 20 new power poles, crews upgraded about a half-mile of distribution lines to connect the two substations. The upgrade will provide system operators with greater flexibility to restore service to area customers more quickly in the event of an outage. Construction began in February and was completed this month.

UniSource also is performing system improvements to transmission and distribution lines between the South Kingman Substation and our Hilltop Substation, located approximately five miles east, near Hualapai Mountain Road. Crews will remove 98 wooden poles and install 84 steel poles along the route, which traverses rugged terrain in some areas.

The steel poles are stronger than wood poles and can be placed farther away from each other. UniSource also will increase the capacity of the 69-kilovolt (kV) transmission line by installing larger wires. New, lower-voltage distribution lines also will be installed on these poles underneath the transmission lines to support local service in the area.

Crews started construction last summer at the Hilltop Substation and have been working their way west  to the South Kingman Substation. Work will continue through the end of this year on this $8 million project.

 Lake Havasu

Crews recently finished upgrading a mile of overhead distribution lines from our Desert Hills substation. The upgrade expands the capacity of the local grid to accommodate future growth in the Crystal Beach area, north of Lake Havasu City. Crews installed about 25 taller, stronger wood and steel poles as well as higher-capacity lines.

UniSource started work on the $370,000 project in February and finished construction last month.

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