30 V.S.A. § 208

A complaint to the Public Utility Commission may be made against a company subject to supervision under the provisions of this chapter concerning any claimed unlawful act or neglect adversely affecting the complainant, who may be a company or five or more individuals or, if less than five are so affected, then any one of them. The complainant may bring his or her complaint directly before the Commission or he or she may file his or her complaint with the Department of Public Service, which shall investigate such complaint and, if sufficient cause exists, shall prosecute the same in the name of the State. Upon request of the trustees of an incorporated village or the selectboard or city council or upon its own motion, the Department of Public Service may institute investigations regarding the price, toll, rate, or rental charged by any utility.