Power Outages

Key Points

The 2003 Northeast Blackout highlighted the fragility and interdependence of the country's electrical system.
The United States power grid is made up of three interconnecting networks. Seattle's power infrastructure is linked to the Western Interconnection, a network of public and private power generators and distributors that serve over 80 million people in the Western U.S., from Mexico to Canada.480.
About half of Seattle City Light's unplanned power outages are caused by falling trees or branches.
Almost 90% of Seattle's power comes from hydroelectric power; 47% of the power Seattle consumes is purchased.481.
Seattle could face power outages due to electrical vault fires, windstorms, or an issue in the regional grid. Seattle has the ability to isolate itself from the grid but cannot supply enough electricity for the city on its own.
The largest impacts of an extended power outage would be economic because most businesses in the affected area would likely shut down.
Seattle's power depends on the health of generating facilities that lay far outside the municipal boundaries, on snow and rain that are the "fuel" for hydroelectric power and finally on the health of the transmission and distribution lines that move the power.
Expected climate and hydrologic changes will likely alter the annual patterns of hydroelectric supply, lowering supply during the summer and increasing supply during the winter.
By 2028, peak demand may not be met in winter without purchasing additional power.