476.71  Purpose.
  It is the intent of the general assembly that a public utility should not directly or indirectly include in regulated rates or charges any costs or expenses of an affiliate engaged in any business other than that of utility business unless the affiliate provides goods or services to the public utility. The costs that are included should be reasonably necessary and appropriate for utility business. It is also the intent of the general assembly that a public utility should only provide nonutility services in a manner that minimizes the possibility of cross-subsidization or unfair competitive advantage.
89 Acts, ch 103, §2