Fog Covered Skyline
Seattle City Light DEBRA SMITH, General Manager and CEO
Vegetation Management
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Vegetation Management

Power Delivery

More than 90% of the power supplied to City Light customers comes from clean hydroelectricity. City Light owns and operates its own hydroelectric facilities and also purchases power through the Bonneville Power Administration. Once power is generated, it moves through an extensive network, known as the power grid, consisting of substations, power lines and transformers. Here is how it works:

  • Power generation - The force of water at a hydroelectric dam facilities pushes and turns turbines to produce electricity. Transformers at the dam then increase the electricity voltage to prepare it for transmission lines that will carry it over many miles to our service territory.

  • Power transmission - Electricity is transmitted through large scale transmission lines over hundreds of miles at high voltages (115 kV or above) to reduce the energy loss which occurs in long-distance transmission. The electricity is delivered to a local substation transformer where the voltage is reduced to prepare it for distribution to homes and businesses.

  • Power distribution – Electricity is delivered from neighborhood substations to homes and businesses through smaller, lower voltage (4 kV-26kV) distribution power lines. Before it enters a building, it travels through another transformer to reduce the voltage for safe use.

With over 657 miles of transmission lines, much of it over rugged terrain, and 1700 miles of distribution lines, our experts work hard every day to keep lines clear of potential dangers and disruptions to service.
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contact us

Ask our arborists a question, share feedback or report an issue using our online form, or call 206.386.1733
Monday-Friday, 8:00am-4:00pm.

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  • Contact Seattle City Light

    700 5th Avenue
    Suite 3200
    P.O. Box 34023
    Seattle, WA 98124-4023


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