Power Outages

Key Points

  • The 2003 Northeast Blackout highlighted the fragility and interdependence of the country's electrical system.

  • About half of Seattle City Light's unplanned power outages are caused by falling trees or branches.

  • More than 86 percent of Seattle's power comes from hydroelectric power

  • 51percent of the power Seattle consumes is purchased.

  • A regional cascading blackout is a distinct possibility in this region. It seems likely that a problem would originate outside the Seattle City Light system because the Bonneville Power Administration transmission system is in need of a major upgrade.

  • 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, snow and rain as fuel for hydroelectric power, and 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 and demand, lowering demand during the winter and increasing demand during the summer.

  • By 2021, demand may not be met in late summer, early fall and winter.

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