SPRINGFIELD - After months of negotiating, the Illinois House and Senate on Thursday both approved a $1 billion deal that forces Ameren and ComEd to give rebates to their customers across the state.

The plan needs Gov. Rod Blagojevich's signature before it becomes law. Spokeswoman Rebecca Rausch said that while the governor has been calling for rate relief, he needs time to look it over.

"We need to review the bill," Rausch said.

If Blagojevich signs off, ComEd and Ameren would begin issuing rebates to customers in September. Most Ameren customers would get checks in the mail. ComEd customers would get credits on their bills.

Customers would get various amounts, but in general the higher someone's rates spiked in January, the bigger the rebate. Both utilities say the credits would refund about half their increases.

Ameren says everyone would get at least $100 for the year, starting with at least an $80 check in September.

The measure passed on an 80-33 vote in the House and a 40-11 vote in the Senate.

Most opposition came from Republicans, some of whom disagreed with the amount of money the deal offers.

State Rep. Mike Bost, R-Murphysboro, said that because lawmakers talked so much about cutting electric rates all the way back to 2006 levels, anything less will be met with disapproval.

"This is crumbs that are being thrown to our constituents," he said. He voted "yes," though, saying there were no other deals to be voted on.

A majority of the deal was hammered out behind closed doors since lawmakers threatened to force the utilities to cut their rates. Republicans had complained that while they sat in some meetings, they were closed out of negotiating the final deal.

Some Democrats disagreed.

"Anyone who wanted to be part of those negotiations could be," said state Rep. Bob Flider, D-Mount Zion.

The $1 billion comes from the utilities and electric generation companies. Exelon and ComEd combined to pay $800 million of the final tab.

And the final deal also includes the creation of a new state agency that supporters say could help keep rates in check in the future.

State Sen. Bill Brady, R-Bloomington, who voted against the measure, remained skeptical of that idea.

"We don't need to create another government entity," he said.

State Sen. Dan Rutherford, R-Chenoa, did not vote.

The measure was sponsored by state Sen. Gary Forby, D-Benton, in the Senate and state Rep. George Scully, D-Flossmoor, in the House.

The legislation is Senate Bill 1592.