The news: Illinois let a 10-year rate freeze on electric bills expire in January, and state residents will face the hottest period of the year with an expected cooling cost increase of about 15 percent.

Behind the news: Low-income Illinois residents could be hit hard this summer by not only higher cooling costs resulting from deregulation, but also a decline in federal funding for electric bill relief.

To offset increases in costs, the state offers energy bill payment assistance plans, such as the federal Low-Income Home Energy Assistance Program that helps residents with incomes no more than 150 percent above the poverty level. Last year, 64,000 households applied for “summer cooling assistance,” with about 50,000 receiving help, said Teresa Kurtenbach, spokeswoman for the Illinois Department of Healthcare and Family Services, which administers the program.

The increase in demand for rate relief will likely be met with less assistance because of an expected decrease in federal support. “We don’t have as much federal funding as we had last year,” said Charles A. Jackson, the department’s deputy director of administrative operations.

Meanwhile, Commonwealth Edison figures that a single-family household that did not use electricity to heat their home paid $132.82 in August last year and will pay $153.17 this August. Company spokesman John Dewey said the figure is based on running 1,500 kilowatt-hours of electricity. “Our peak demands occur in the summertime,” he said.

David Kolata, executive director of the Chicagobased watchdog group Citizens Utility Board, said such increases will force the state’s vulnerable residents to make tough choices. “ComEd will continue to be making record profits while seniors choose between paying for prescription drugs and air conditioning,” he said.