Mich. Comp. Laws § 18.1712

Sec. 2. "Cost-effective" means that the present value to a governmental unit of the energy, utility, capital cost avoidance, capital improvement, and operational costs and revenues reasonably expected to be saved or produced by a facility, activity, measure, equipment, or system over its useful life, including any compensation received from a utility, is greater than the net present value of the costs of implementing, maintaining, and operating such facility, activity, measure, equipment, or system over its useful life, if discounted at the cost of public borrowing.