A transformer outside the plant steps up the voltage from 2,300 volts to 23,000 volts for transmission to Juneau. The transmission line is 12 miles long and from the Powerplant goes along the Taku, up the Sheep Fork of Carlson Creek, over the top of Sheep Mountain, and down into Sheep Creek Valley, originally ending at the Alaska Gastineau Mill. Today the line continues into Thane Substation. Much of the transmission line has been rebuilt, but some of the original towers are still in service. The construction of the transmission line was an impressive feat in 1915.

Click here to read a 2009 article on the construction of the Annex Creek transmission line written by Al Shaw for the Gastineau Heritage News, a publication of the Gastineau Historical Society.