Xcel Energy, which serves 1.4 million Colorado residents, filed for a $142 million increase in electricity rates Tuesday, a move that would raise the average residential bill by up to $4 a month.

The request was filed with the Colorado Public Utilities Commission, and the company seeks to have the new rates in place by Dec. 23.

The commission will probably defer a decision until next year so public hearings can be held, said Mark Stutz, an Xcel spokesman. In the meantime, Xcel will ask for a $100 million interim rate increase to go into effect in January.

The proposed increase would raise the average residential monthly bill to $71 for 632 kilowatt-hours and increase small-business bills by $5.30 a month to $115 for 1,123 kilowatt-hours.

Xcel has filed for three rate hikes totaling $391 million since 2007, which raised bills by about 20 percent.

“Since our last electric-rate case, we have added more than $750 million of investment in Colorado to meet our customers’ needs,” David Eves, chief executive of Public Service Co. of Colorado — an Xcel subsidiary — said in a statement.

“No one wants to see their bills increase, especially during difficult economic times, but this rate change is needed to meet our commitment,” Eves said.

The exact rate hike will depend on which costs and credits proposed by Xcel are accepted by the PUC.

Among the largest elements in the rate request are:

• $52 million in costs that customers will absorb as a result of expiration of a purchase power agreement Xcel had to supply Black Hills Energy with 300 megawatts of power.

• $23 million more in state and local property taxes Xcel expects to pay.

• $23 million in new and upgraded power lines.

• $13 million in investments to close old coal plants and replace them with cleaner-burning natural gas as required under state law.

• $10 million in beetle-kill tree removal.

“We are trying to get to those dead trees before they knock down our lines,” Stutz said. “Our service area goes from the Front Range to Grand Junction, so we have lines in the mountains.”

Mark Jaffe: 303-954-1912 or mjaffe@denverpost.com