Residents of Chicago and the North suburbs may see higher gas bills.
The parent company of Peoples Gas and North Shore Gas filed for rate hikes Tuesday.
The plan by Chicago-based Integrys could mean an extra $4 a month to the average residential North Shore bill and $6.50 a month for Peoples Gas customers.
A consumer watchdog group Citizens Utility Board says it will "study this proposal line by line and fight every penny the companies can't justify."
The Chicago Tribune reports that Integrys was forced by the Illinois Legislature to seek increased rates because the company refused to buy from a plant in Chicago that will convert coal to natural gas.
The Illinois Commerce Commission will decide on the rate request after an 11-month review.