SPRINGFIELD - A panel of Democrats voted Thursday to cut Illinoisans' power bills and slap a tax on large electric generation companies to do it.

The lawmakers want to tax the state's generating companies to bring in $2 billion to help cut rates and refund money to Ameren and ComEd customers who have struggled to pay higher bills.

They say taking the money from the generating companies that get most of the new profits from higher electric rates would negate the argument that the utilities, which only deliver the power, would suffer if rates were cut to 2006 levels.

After listening to two hours of testimony, a House panel approved the tax by a 5-4 along party lines Thursday evening. It now moves to the full House.

The plan's sponsor, state Rep. George Scully, said the plan taxes companies' "privilege" to generate electricity in Illinois.

"It is a burden for the state of Illinois to be a host to these utility companies," the Flossmoor Democrat said.

But much like the way in which disputes between House and Senate lawmakers have stalled a plan to roll back rates for months, the Senate might not warm to the House's new idea.

State Sen. Gary Forby, D-Benton, would control the legislation if the House eventually approves it. He said Thursday that Senate President Emil Jones, D-Chicago, might keep it bottled up.

In addition, Forby said a new tax on generators could prevent more power plants that use Illinois coal from being built.

"We don't want to run them off," he said.

Jones spokeswoman Cindy Davidsmeyer said the Senate president hasn't formed an opinion yet.

Here's how the House's plan would work: Companies that generate power in Illinois, such as Exelon, Midwest Generation and Ameren's generation division, would be taxed. The money generated would go into a special state fund.

In the meantime, ComEd and Ameren electric rates would be cut to 2006 levels and the companies would pay out refunds from the higher rates customers have already paid in 2007. Then, the money in the state fund would be given to the utility companies so they would come out even.

But utility officials say it's not that simple. The three Ameren subsidiaries in Illinois, for example, would have to pay out around $1 billion before they got any money back from the state.

"We don't have that kind of cash available to us," said ComEd chief financial officer Bob McDonald.

Even if the full House and Senate approve the new tax, a spokesman for Ameren's generation division said the company would challenge it in court. The utilities also plan to challenge a rate rollback in court if it's approved.

Earlier this week, reports showed that utilities and generation companies had offered to pay out $500 million to Illinois customers if lawmakers would back off their plans. But some said half a billion dollars wasn't enough.

A vote from the full House on the new proposal could come as early as today.