Mich. Comp. Laws § 460.652

Sec. 2. The Michigan public service commission may prescribe by rule all of the following: (a) The circumstances under which a utility may require a guaranty deposit. (b) The amount of the guaranty deposit. (c) The interest rate payable on the guaranty deposit. (d) The method by which the utility will pay interest on the guaranty deposit to the ratepayer. (e) The circumstances under which the guaranty deposit must be returned to the ratepayer.