The Idaho Public Utilities Commission approved changes to Avista Corporation’s annual rate adjustments that will lower residential electric bills by $4.85 per month, according to the agency’s Oct. 2 press release. The fixed cost adjustment, a mechanism that allows customers to receive a rebate when the utility’s revenue surpasses costs and incur a surcharge when expenses are higher, accounts for $4.16 of the decrease. The company said that the fixed cost change is due largely to higher energy use last year. The power cost adjustment, which reflects differences between costs included in customer rates and actual costs incurred to procure power for customers, contributed to the rate cut due to low power prices in the wholesale market. The third adjustment is a result of a credit provided to customers to share the benefits of the Columbia River hydropower system.