CHICAGO (CBS) – One issue on the ballot next month is aimed at saving residents in Chicago and across the suburbs hundreds of dollars a year on their power bills.

It’s called electric aggregation, which allows cities and towns to change power companies to buy power for their residents at bulk rates.

CBS 2’s Derrick Blakley takes a look at the pros and cons of those kinds of power switches.

West suburban Glen Ellyn is one of nearly 300 communities and counties where voters will decide on Election Day whether to buy their electricity from a provider other than ComEd.

Kristen Schrader, assistant to the Village Manager in Glen Ellyn, said, “What other municipalities have seen is a savings between $150 and $300 annually, per resident.”

Last January, Oak Park became the first Chicago area suburb to take that step, with residents pocketing the savings.

Residents said their bills have gone down since then, with one Oak Park resident estimating she pays 20 percent less on her electric bill.

Oak Park signed on with Integrys Energy, negotiating a rate of 5.78 cents per kilowatt hour. ComEd’s standard rates range as high as 8.32 cents a kilowatt hour. That’s a maximum savings of 30 percent.

Oak Park sustainability manager K.C. Poulos said, “If you project that out to the end of the year, we’re going to be saving well over $2 million as a community.”

Even for towns that switch, ComEd still provides customer service and mails the bills.

Energy consultant Dave Hoover has been providing guidance to 25 Illinois towns where voters will decide on Election Day whether make the change.

“From a resident’s point of view, it’s the clearest win-win situation that I’ve seen in a long time,” he said.

ComEd isn’t affected by communities that switch electricity providers, because the utility only distributes electricity, it doesn’t generate it.