CHICAGO (CBS) — Ahead of an energy rate hike at ComEd next month, a utility watchdog group said it’s seen a dramatic increase in complaints about some of the practices of several alternative electricity companies.

Citizens Utility Board spokesman Jim Chilsen said many alternative energy suppliers are “acting above board,” but that there are others that are not.

He said, in the last 12 months, “Illinois’ electricity market has become more expensive, confusing and treacherous.”

Chilsen said complaints to CUB have jumped by 115% between January and April of this year, compared with the same period last year.

People have complained about rates as high as 15 cents and even 35 cents per kilowatt hour, when ComEd will be charging 7.6 cents per kilowatt hour when its rates go up on June 1.

Chilsen said one Melrose Park woman complained her rates with Major Energy skyrocketed from 7 cents to 35 cents per kilowatt hour.

“Illinois’ electricity market has become a buyer beware market, and we just want consumers to look for red flags of rip-offs and be on the alert,” Chilsen said.

CUB advised consumers to compare electricity rate plans at Chilsen said consumers should ask questions before signing up with an alternative energy supplier — such as how does the company’s rates compare with ComEd’s, and whether the initial rate offered is “an introductory offer” that could “go through the roof in a month or two.”

Read CUB’s full report on the Illinois electric market here.