(Crain's) — State utility regulators Wednesday granted Commonwealth Edison Co. a rate hike that they say will add $4.50 to the average customer's monthly electric bill.

That would be a 5.5% increase over the current average household bill of $81.

The vote by the Illinois Commerce Commission was a victory for the utility. In approving the roughly $270-million increase, commissioners rejected a $218-million hike recommended by an administrative judge in the case. Instead, the regulators sided with a compromise proposal agreed to by ComEd and staff of the ICC.

ComEd originally asked for $360 million but brought its request down after discussions with ICC staff.

"We're disappointed in the decision today," said David Kolata, executive director of the Citizens Utility Board, a consumer watchdog group. "We think the facts clearly show a big increase isn't warranted. We'll do everything we can to overturn it."

A ComEd spokeswoman had no immediate comment, saying the utility hadn't yet reviewed the actual language of the order.

In addition, the ICC tentatively approved ComEd's request for a new rate-setting mechanism that would pave the way for implementation of a "smart grid," a tech-savvy metering system giving customers real-time information on their usage that could lead to systems allowing users to save money by curtailing power consumption during times of heavy demand.

But the commission isn't yet funding the proposal, allowing for future negotiations between consumer groups, ICC staff and ComEd over the details.

Mr. Kolata said the potential for a "consumer-friendly" smart grid was the one silver lining to come out of Wednesday's ruling.

The rate hike, which applies only to ComEd's charge for delivering power to households and businesses in Northern Illinois, is the latest in a series of increases that have raised average electric bills about 35% since a 10-year freeze on rates was lifted at the beginning of 2007.

And customers should brace for more.

An executive with ComEd parent Exelon Corp. told investors at a conference in New York last week that ComEd intends to file for another rate hike in the first half of next year. If approved by the ICC, that would take effect sometime in the first half of 2010.