S.D. Codified Laws § 49-34A-26
On its own motion or upon a complaint made against any public utility, by the governing body of any political subdivision, by another public utility, or by any twenty-five consumers of the particular utility that any of the rates, tolls, tariffs, charges, or schedules or any joint rate or any regulation, measurement, practice, act or omission affecting or relating to the transmission, delivery or furnishing of natural gas or electricity or any service in connection therewith is in any respect unreasonable, insufficient or unjustly discriminatory, or that any service is inadequate or cannot be obtained, the Public Utilities Commission shall proceed, with notice, to make such investigation as it may deem necessary and take such action as deemed necessary and appropriate.
SDCL 49-34A-26