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Powering Seattle through the 21st Century

Seattle City Light is designing its first new electrical power substation in 30 years. The Denny Substation will serve businesses and residents in the commercial areas and residential neighborhoods throughout our service territory, as well as alleviate the distribution congestion in the areas of South Lake Union, Cascade, Denny Triangle, Uptown, Belltown and First Hill. It will provide the higher level of reliability and electrical load density needed by our major medical centers, bio-tech research facilities, and high tech industries, and by current and future manufacturing and innovative entrepreneurial industries.

Located near Denny Way and Stewart Street, the Denny Substation is being designed to support and serve the future expansion and anticipated growth of the area. The specific technical components of the substation include:
  • 115 kV GIS switchgear
  • 3 - 75 MVA 115/13 kV power transformers
  • 13 kV Arc-Resistant Metal Clad Distribution Switchgear
A new transmission line from the Massachusetts substation in SODO will be added to provide power to the Denny Substation. An underground distribution system that connects and provides electricity to customers will also be built. To learn more, click here.

Denny Substation Design - Not your typical substation

Seattle City Light is committed to designing a substation that will fit with the neighborhood, advance community goals, and serve as a model for environmental sustainability.

Though the majority of the site will be utilized for substation operations, City Light and the project team are exploring opportunities to advance neighborhood goals and priorities. The team is taking guidance from existing planning documents such as the South Lake Union Neighborhood Plan and Urban Design Framework, and the Denny Triangle Neighborhood Plan. The design team will use these documents and others as starting points for the design of the substation.

Additionally, the project team will continue reaching out to and working with the neighborhoods and other stakeholders to ensure the community is involved in the final design of the substation. We want to hear from you. If there is something you would like the project team to consider as the design of the Denny Substation progresses, please let us know by emailing

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