Among the hardest hit: FirstEnergy and independents such as NRG Energy Inc. and Calpine Corp. that sell electricity in competitive markets. These companies have already been hurt by a plunge in the price of natural gas, which sets the price of electricity in most markets.

FirstEnergy, which owns 10 regulated utilities from Ohio to New Jersey, said in a Sept. 19 statement it would fire 200 workers due to "continued slow customer load growth and an abundance of electric generation supply resulting in lower power prices."

Oklahoma Gas & Electric, OGE's utility based in Oklahoma City, is among power companies shifting their business models to emphasize saving as well as selling power.

By encouraging consumers to cut back power-hogging air conditioning during sultry weather when demand is greatest, OG&E hopes to postpone building a new fossil-fuel plant this decade to meet growing demand.

Deferring Investment

"Power plants are expensive and those costs are ultimately borne by customers," Brian Alford, a spokesman for the utility, said in a telephone interview. "Our goal is to defer the need for that investment."

The company has shaved an estimated 64 megawatts off of its total daily summer peak demand through a variable pricing program.

About 40,000 customers pay as much as 46 cents a kilowatt- hour from 2 p.m. to 7 p.m. on weekdays, when stress on the grid is greatest, Alford said. Peak rates far exceed the flat 10-cent per kilowatt hour charged other utility customers. Still, program participants can slash spending by running power-hogging appliances like air conditioners from 7 p.m. through 2 p.m., when they pay just 5 cents per kilowatt hour.

TXU Plan

Texas officials are pushing programs that reduce power use during peak periods as the state grapples with a projected shortage of generation reserves in three years as its economy grows.

TXU Energy, the Dallas-based power retailer owned by Energy Future Holdings Corp., recruited customers like Rhea who would let the company shut off their air conditioning when high demand strains the grid on the hottest days.

More than 20,000 customers have signed up for TXU's program, which can reduce demand by as much as 45 megawatts during high energy use, Amanda Ray, a spokeswoman for TXU Energy, said in an e-mail.