Transmission Services

City Light owns 653 circuit miles of high-voltage transmission lines in the Seattle area of the Pacific Northwest. Transmission lines move electricity more efficiently than lower-voltage distribution lines, which deliver power directly to customers. Our transmission lines are typically 230,000, or 115,000 volts. 

We offer non-discriminatory access to our transmission system through our Open Access Transmission Tariff.

Open Access Transmission Tariff (OATT)

In 2009, Seattle City Light adopted an OATT mirroring the pro forma OATT established by the Federal Energy Regulatory Commission. Seattle City Light updated its OATT with approval of the Seattle City Council in 2020, with an effective date of the updated OATT provisions of January 1, 2021.

Tariff includes terms and conditions, rates and service agreements that govern how others can transmit their electricity between points on City Light's transmission system.

Facility Interconnection addresses the processes, technical specifications and agreements that govern how others can interconnect to City Light's transmission system.

Transmission Planning (coming soon) explains the coordinated open and transparent process City Light uses to evaluate and plan for the reliability and adequacy of our electrical system necessary to serve our customers.

Contact us for more information about our transmission services.