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The Colstrip Transmission System was built in the early 1980s to move power from the Colstrip generating facilities to transmission systems in western Montana. The Colstrip Transmission System is jointly owned by NorthWestern Energy, Avista Corporation, Portland General Electric, Puget Sound Energy and PacifiCorp. 


The Colstrip system is made up of two 500 kilovolt segments. The first runs from Colstrip to Broadview. The second runs from Broadview to Townsend. At present, Colstrip power moves across the Bonneville Power Administration’s (BPA) transmission system west of Townsend before reaching local utility customers and BPA’s main grid.




As a Washington-state based utility, PSE must plan to meet the requirements of the Clean Energy Transformation Act, which require electric utilities to transition to a carbon-neutral supply of electricity. In order to comply with state law, PSE must remove coal from its portfolio by the end of 2025.


There is significant interest in developing renewable resources in Montana and already there have been several agreements for new renewables to interconnect to the Colstrip Transmission System with more expected to come. PSE is committed to investing in Montana renewables and has already taken some initial steps in investing in new wind in Montana through the Clearwater Wind Project power purchase agreement. 


While retirement dates have not been established for Colstrip Units 3 & 4, additional transmission capacity will likely become available at the time the units transition. Access to any available transmission capacity can only be obtained by following the Federal Energy Regulatory Commission (FERC) rules. Additionally, access would need to meet requirements under the Montana Intertie Agreement and its successor arrangements upon renewal. 


We are updating this video to explain the impacts of Washington State's Clean Energy Transformation Act. In the meantime, this piece does a good job explaining how transmission work and the considerations that must be made as new resources and capacity become available:

Please visit our FAQ section for more transmission information. 

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