Topeka ? Kansas regulators on Friday approved a $32 million increase in electric rates for Westar Energy Inc., raising customers’ monthly bills for the third time this year.

The latest increase takes effect Monday and will help Westar pay for improvements on pollution-control equipment at its generating plants.

Westar said monthly electric bills will increase by an average of $2.95 for residential customers in its northern division. That region includes Lawrence, Emporia, Hutchinson, Olathe, Parsons, Salina and Topeka.

In its southern division, Westar said the monthly increase for residential customers will average 88 cents. The region includes Wichita, Arkansas City, El Dorado, Independence, Newton and Pittsburg.

The Kansas Corporation Commission’s order approving the rate increase and called the costs Westar incurred “prudent” and “reasonable.” Most of the environmental upgrades were at its largest generating plant, the coal-fired Jeffrey Energy Center, about 30 miles northwest of Topeka.

“These upgrades are federally mandated, but they’re the right thing to do,” Westar spokeswoman Erin LaRow said in an interview. “It’s important to us and important to our customers that we’re good stewards of the environment.”

Westar, the state’s largest electric company with about 674,000 customers, had been granted two rate increases totaling $162 million earlier this year.

The KCC allowed Westar to raise its rates in January by $130 million, to recoup higher operating costs and cover repairs following a December 2007 ice storm. In March, the commission approved an additional $32 million to offset costs in upgrading transmission lines.

The Citizens’ Utility Ratepayers Board, which represents small businesses and residential customers, predicts rates will keep rising.

The KCC plans to have hearings this summer on raising Westar’s rates again, partly to cover its investments in wind farms. And Westar announced plans earlier this month to spend up to $380 million upgrading pollution controls at its coal-burning plant outside Lawrence.

Still, David Springe, CURB’s chief attorney, said “there wasn’t a lot to argue about” when Westar sought higher rates this year to cover what it had spent on environmental upgrades.

“Frankly, Westar spent money,” he said. “We will get clean air, but it’s going to be expensive.”

In regular trading Friday, shares of Westar closed up 23 cents at $17.85 on the New York Stock Exchange.