Soaring electricity costs have taken a bite out of the bottom line at Ken Clarida’s restaurant in the southern Illinois town of Benton, prompting him to raise prices, including a 50-cent markup on hamburgers, to $1.99.

Clarida, who’s also grappling with a recent $1-an-hour increase in the state’s minimum wage, got some good news Monday with the announcement by Ameren Corp. that long-awaited rate relief was on the way in the form of rebate checks or bill credits.

St. Louis-based Ameren said it would begin mailing the checks Wednesday to its Illinois customers.

Ameren held news conferences to trumpet the $140 million in relief to its customers in central and southern Illinois, promising each customer at least $100 back by the end of the year – $85 through the initial checks or credits, the rest through monthly credits.

Customers who don’t use electricity to heat their homes will get about $130 back this year, and customers who have electric heat will get about $400. The deal rolls back the increases customers paid this year by about half, with the actual rebate tied to total electric usage.

The checks and credits are part of a $1 billion rate relief package negotiated by the utilities and state lawmakers to ease customer outrage after a 10-year rate freeze ended in January and electric bills spiked for many consumers in Illinois. Gov. Rod Blagojevich signed the package into law two weeks ago.