Consumers of Commonwealth Edison Co. are due to receive refunds of summer rate overcharges that could amount to up to 20 percent of their total electric bill for the last seven months, according to an analysis conducted by the Citizens Utility Board.

CUB might win the tentative refunds as a result of a six-month lawsuit during which the consumer group charged that a rate restructuring, approved for Edison by the Illinois Commerce Commission in June, resulted in illegal and excessive rates.

The rates restructuring reduced the company’s summer rates by 12 percent, but increased non-summer rates by more than 63 percent for the typical customer.

The Illinois Appellate Court agreed with CUB’s claims in Dec. 30 ruling, the overcharges. Edison is trying to block the possible refunds with an appeal to the Illinois Supreme Court – a move CUB is fighting.

Since the ruling, the ICC has appeased the demands of CUB by developing a compromised rate proposal with Edison. The new proposal will allow the company a 2 percent rate increase for 1989, followed by a 3 percent hike in 1990. The end result, Edison contends, will be a freeze on rates through 1994.

Pat Clark, spokewoman for CUB, said, “Actually, the average residential customer will see his rates go up 6 percent in 1989, and likely another 6 percent in 1990.”

“This is the second time in a row that the courts have agreed that Commonwealth Edison’s ratepayers are not getting a fair shake from the Illinois Commerce Commission,” CUB President Josh Hoyt said, referring to the utility’s 1985 rate hike which also was overturned by the courts.

CUB Research Director James Seidita said that of the four major electrical utilities in Illinois, Edision has the highest rate per kilowatt-hour at 14 cents, while the other utilities charge six or seven cents. “There is a definite correlation between nuclear power plants and higher rates.” He said the utilities that don’t own nuclear reactors have considerably lower rates. Edison currently owns 12 of 13 nuclear power plant in Illinois.

Residential customers of Edison might remember bills issued in November that contained a fuel adjustment refund averaging between $10 and $12 per consumer.