Aug. 10--DANVILLE -- Illinois customers with a day-trader's attitude can save nearly 15 percent on their electricity bills under a new program offered by Ameren.

The two-year-old Power Smart Pricing program was created after Illinois legislators -- at the urging of power industry watchdog Citizens Utility Board -- required state utility companies offer pricing programs rewarding customers for "green" diligence.

Area Ameren customers received information on the program with this month's bill, but so far only 5,000 Illinois customers have signed up. Ameren subsidiaries serve some 2.4 million electric customers in Illinois and Missouri.

"I don't think that many people know about it yet," said Jim Chilsen, CUB communications manager. "It can be a big money-saver for the right customer and there are very specific things you should consider. It's a good program, but it's not for everyone."

The program offers customers the ability to track in real time, via the Web, the day-ending regional commodity price of elec-tricity. And as the rate fluctuates, participants can adjust their usage to avoid peak rates the following day.

"You don't have to turn everything off and you don't have to sit around in the dark," said Stephanie Folk, a spokeswoman for CNT Energy.

CNT Energy is a non-profit that by law must operate and market the program separately from Ameren.

She said it's more a matter of knowing when the prices are high or are going to go higher, and then saving major chores such as laundry for a less-expensive part of the day.

"Maybe you just turn up the air conditioner a couple of degrees at certain times," she said.

The power used is still based on kilowatt hours, but under the program, an hour of power can cost customers more or less based on the time of day and its fluctuating price. The old system simply charges for total hours used.

Participants who pay a monthly fee of $2.25 will receive installation of a new, digital meter and access to special "spike alerts" by e-mail if power-market prices rise precipitously.

She said from May 2007 to May 2009, customers saved an average of 13 percent on their bills, a number Chilsen said was likely sound.

That number may change after the mild summer as prices have remained stable amidst lower air-conditioning use, which also decreases the value of electricity on the market and makes for a lower rate.

"In a normally hot year, the highest prices will be in the mid-afternoon," Folk said, when demand is highest.