Whenever there is filed with the Commission by any public utility any schedule stating a new rate, the Commission may, either upon complaint or upon its own initiative, upon reasonable notice, enter upon a hearing concerning the lawfulness of such rate.
47 Del. Laws, c. 254, § 5; 48 Del. Laws, c. 371, § 10; 26 Del. C. 1953, § 152; 59 Del. Laws, c. 397, § 1.