The state corporation commission, in determining the reasonable value of property under Kan. Stat. Ann. § 66-128, and amendments thereto, shall have the power to evaluate the efficiency or prudence of acquisition, construction or operating practices of that utility. In the event the state corporation commission determines that a portion of the costs of acquisition, construction or operation were incurred due in whole or in part to a lack of efficiency or prudence, or were incurred in the acquisition or construction of excess capacity, it shall have the power and authority to exclude all or a portion of those costs from the revenue requested by the utility.

For the purpose of this act, “excess capacity” means any capacity in excess of the amount used and required to be used to provide adequate and reliable service to the public within the state of Kansas as determined by the commission. The commission may in its discretion prohibit or reduce the return on costs which were incurred in constructing, maintaining or operating excess capacity.