July 2 (Reuters) - The biggest power grid in the United States expects electricity use to reach the highest level so far this year as homes and businesses crank up their air conditioners to escape a heat wave baking parts of its Mid Atlantic and Midwestern service area.
PJM Interconnection, the region's power grid operator, forecast electric demand would peak at around 151,000 megawatts on Monday. One megawatt can power about 1,000 U.S. homes.
That would be the highest power usage in the area so far this year and would top last summer's high of 145,331 MW, but would fall well short of the grid's all-time peak of 165,492 MW set in the summer of 2006, said PJM spokesman Jason McGovern.
As cooler weather moves into the Midwestern part of its grid, PJM forecast peak demand would only reach about 149,000 MW on Tuesday.
PJM operates a grid serving 65 million people in all or parts of 13 states from New Jersey to Illinois. The two biggest cities in PJM are Chicago and Philadelphia.
Meteorologists forecast the mercury would hit 99 degrees Fahrenheit (38 degrees Celsius) in Philadelphia on Monday before slipping to 96 on Tuesday and 91 on Wednesday after reaching the mid-90s over the weekend.
In Chicago, however, highs were expected to drop from the mid-90s over the weekend to the low 80s on Monday and Tuesday.
PJM issued hot weather alerts over the weekend asking the companies that operate generation and transmission facilities in its service area to avoid any unnecessary equipment maintenance during the heat wave.
The biggest power companies in PJM include units of Duke Energy Corp, Exelon Corp, FirstEnergy Corp , American Electric Power Co Inc, Dominion Resources Inc and Public Service Enterprise Group Inc .
In New York, meanwhile, the New York Independent System Operator (NYISO), which operates that state's power grid, said it may activate its emergency demand response program on Monday.
Power companies use demand response programs to reduce electric usage when supplies are tight or for economic reasons to lower the cost to buy power when prices spike. Consumers participating in the programs receive lower rates or some other form of compensation for reducing usage when their power providers issue a request.
The biggest power companies in New York include units of Consolidated Edison Inc, National Grid Plc, Iberdrola SA, Entergy Corp, TransCanada Corp and NRG Energy Inc. (Reporting by Scott DiSavino; editing by Jonathan Oatis)