Topeka ? Rates charged by the state’s largest retail natural-gas supplier would increase by $45 million a year under an agreement between the company and other parties.

Kansas Gas Service Inc., the staff of the Kansas Corporation Commission and the Citizens’ Utility Ratepayers Board filed the agreement Monday with the KCC, which regulates utilities. CURB represents residential customers and small businesses.

The commission already has a hearing on the company’s rates set for today and must decide whether to accept the agreement. The commission has until Sept. 29 to make a decision on KGS rates.

Kansas Gas Service does not provide natural gas to the Lawrence area, but does serve several of the state’s largest cities, including Kansas City, Topeka and Wichita.

David Springe, CURB consumer counsel, estimated that residential customers would see their bills increase on average between $60 and $70 a year, or between $5 and $6 a month. However, homes use the bulk of their gas in the winter.

The company sought to increase both its monthly service charge and the rate it charges consumers for transporting gas.

Springe said although the proposed rate increase represented “a big number,” the agreement represented a fair settlement. He noted that the company hasn’t sought a rate increase since 1996.

“They have spent a lot of money on the system,” he said. “They legitimately needed some money.”

The company, which serves about 642,000 customers in Kansas, initially sought $76 million from higher rates. It argued the money was necessary to offset higher operating expenses and the cost of improvements to its pipeline system.

The company has said that since 1996 its investment in its utility property increased from $455 million to $655 million, about half of the total financed with debt.

Last month, KCC staff recommended a rate increase of $28.7 million, and CURB’s figure was $31.5 million.

But the agreement won’t cover the wholesale price of natural gas, which the KCC doesn’t regulate — and which often represents 70 percent of a customer’s bill each month.

CURB and advocates for the needy have worried that gas prices will spike this winter. Earlier this year, U.S. Department of Energy officials worried the price could rise this winter to $9 per thousand cubic feet — or three times last year’s price.