In the fall of 2019 NorthWestern Energy will begin upgrading the 109-year-old turbines and generators in the Madison Powerhouse downstream of Ennis Lake. The original powerhouse building will remain in place, largely unaltered, while four new turbine-generator units are installed within it. No alterations to the dam or flow conveyance structures are required by the project.
As a result of the highly efficient and modern equipment the peak capacity of the powerhouse will increase from 8 Megawatts to 12 Megawatts. The new turbines will efficiently harness 95% of the power available from the water at the same flows used under the existing license, and that will result in almost 15,000 additional megawatt-hours for an average water year.
Construction work is scheduled to begin this fall at which time the powerhouse will be shut down and water usually conveyed through the powerhouse will be passed through the bypass channel. During some of the construction project, flows in the bypass channel between Madison Dam and Powerhouse will be increased significantly, but flows downstream of the plant will be unaffected during the project
The four generating units will be updated to a modern design, moving from two turbines per unit to just one. In addition to increased energy capacity and efficiency compared to the present generators, the new units will also be more fish friendly.