Senate Bill 1125 aims to revise the priorities for siting electric transmission facilities in Wisconsin, specifically focusing on mega transmission systems. The bill establishes that, to the extent feasible and consistent with economic, engineering, reliability, and environmental considerations, the first priority for siting these systems should be either consolidated utility corridors or high-voltage direct current systems and other underground facilities that are located alongside existing high-voltage transmission lines or within the right-of-way of major highways and railroads. This new priority structure replaces the previous order, which emphasized existing utility corridors, highway and railroad corridors, recreational trails, and new corridors.

The bill also includes a renumbering of existing legal language, specifically changing the designation of 1.12 (6) (a) to 1.12 (6) (ar), while creating a new section, 1.12 (6) (ag), that outlines the updated priorities for mega transmission systems. The definition of a mega transmission system is specified as a high-voltage transmission line designed for operation at a nominal voltage of more than 400 kilovolts. This legislative change reflects a shift towards more efficient and environmentally considerate siting practices for large-scale electric transmission infrastructure in the state.