(Adds temperature and power demand forecasts)
June 30 (Reuters) - U.S. power grid operator PJM Interconnection on Monday declared a hot weather alert for its mid-Atlantic region, telling its electric company members to prepare for expected heavy air conditioning demand on Tuesday and Wednesday.
PJM, which operates the biggest U.S. power grid with 183,200 MW of installed capacity serving 61 million people, said in an email it may ask members in the region to “carry additional reserves to cover increased levels of operational uncertainty.”
But the grid operator said it has not called on additional power plants to sit in reserve.
PJM forecast demand for power would rise from about 134,700 megawatts on Monday to 143,100 MW on Tuesday before declining to 136,200 MW on Wednesday and 121,900 MW on Thursday.
That would still be well below the grid’s highest peak power use of 165,492 MW in July 2011. One megawatt powers about 800 to 1,000 homes.
Temperatures in Philadelphia, the biggest city in PJM’s mid-Atlantic region, are expected to rise from 88 degrees Fahrenheit (31 Celsius) on Monday to 92 degrees (33 C) on Tuesday and Wednesday before declining to 86 degrees (30 C) on Thursday, according to weather forecaster AccuWeather.com.
PJM serves all or parts of 13 mid-Atlantic and Midwest states, from New Jersey to Illinois and including the District of Columbia.
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 . (Reporting by Scott DiSavino; Editing by Chris Reese and Paul Simao)