Wyo. Stat. § 37-3-115: Rates; less expensive source of supply.

In the case of a utility furnishing natural gas, if the utility decreases its cost of natural gas, not less than ninety percent (90%) of the decrease in the cost shall be passed on to the consumer and in addition to other factors allowed by the commission in setting rates the commission may allow the utility to add to its rate not more than ten percent (10%) of the difference between its previous cost for natural gas and its new cost for natural gas.