Any person may file a written complaint with the board requesting that the board determine compliance by a public utility with the provisions of section 476.78, 476.79, or 476.80, or any validly adopted rules to implement these sections. Upon the filing of a complaint, the board may promptly initiate a formal complaint proceeding and give notice of the proceeding and the opportunity for hearing. The formal complaint proceeding may be initiated at any time by the board on its own motion. The board shall render a decision in the proceeding within ninety days after the date the written complaint was filed, unless additional time is requested by the complainant.