Avista customers in Washington will see their electric rates go up 7.2 percent and their natural gas rates rise 3.2 percent starting Dec. 1, according to an agreement pending state approval. Under terms of a rate case settlement agreement announced this morning, the rate hikes would boost Avista’s annual electric revenues by $29.5 million and natural gas revenues by $4.6 million. If approved by the Washington Utilities and Transportation Commission, the new rates would mean a residential customer using an average of 1,000 kilowatt-hours of electricity per month would pay an additional $5.62 per month, for a revised bill of $77.41. A residential customer using an average of 69 therms of natural gas per month would see a $2.17 monthly increase, for a revised bill of $62.20. Avista’s original request in March was for an electric rate increase of 13.4 percent, or $55.3 million in increased annual electric revenues. The lower increase reflects in part an $11.7 million decrease in power supply costs, primarily due to the decline in natural gas fuel prices. The Spokane-based utility in March also had requested to raise natural gas rates by an average of 6 percent, or $8.5 million in additional annual revenue. The lower amount in the settlement is due in part to additional natural gas storage to be used starting next May. Other parties to the settlement are the staff of the state Utilities and Transportation Commission, the Public Counsel Section of the Washington Office of the Attorney General, Northwest Industrial Gas Users, Industrial Customers of Northwest Utilities and The Energy Project. The commission is not bound by the settlement. “We believe the settlement agreement represents a fair and reasonable outcome for our customers and for our shareholders,” Dennis Vermillion, Avista Corp. senior vice president and president of Avista Utilities, said in a news release. “The agreement is the result of concessions and compromises on a number of issues to arrive at an outcome that is supported by all parties in the rate filings. It also represents continuing progress in our efforts to timely recover the costs of serving our customers.”