TUB serves nearly 10,000 residential, commercial and industrial customers with low-cost, reliable power. Over 250 miles of distribution lines are maintained by the electrical department, which includes line workers and grounds workers, two engineering associates and an electric department manager. In addition to line maintenance, crews are also on call 24 hours a day for power outage emergencies. TUB provides power through two main 161 kV substations, the most recent one being constructed by TUB staff and energized in March of 1997. Each main substation has the capacity of 75 MVA and each typically carries a winter peak load of 32 MW. The TUB distribution voltage is nominally 13 kV, three phase, 60 hertz. TUB is a power distributor for the Tennessee Valley Authority, which has provided low-cost, reliable, public power to the customers of Tennessee and portions of surrounding states since 1933.