Counting the Power Failures - NYTimes.com As my colleague John Schwartz reports in The Times, Friday night's storms left millions of people in sweaty darkness. Just how much electric load was unplugged? About as much as it would take to serve the metropolitan areas of Pittsburgh and Dayton, Ohio, according to an informal calculation by PJM, the regional grid operator. The letters used to stand for Pennsylvania-Jersey-Maryland, but the organization now manages the moment-to-moment supply of electricity for 60 million people in all or part of 13 states plus the District of Columbia. Paula DuPont-Kidd, a PJM spokeswoman, said that local losses of power had reduced demand by 5,000 to 6,000 megawatts. That's about as much as the output of 10 full-size coal plants. On Saturday, she said, peak demand had been expected to reach 133,000 megawatts. But because of the blackouts caused by damage to the distribution system and because lower-than-expected temperatures had air-conditioners working less hard, it rose to only 120,000 megawatts, Ms. DuPont-Kidd said. Sluggishness in the economy, especially industry, has depressed the demand for power over all, and the grid has plenty of capacity this year, she noted. So far "the system hasn't been stressed"" in 2012, she said, and PJM has made no emergency appeals to customers to conserve energy. "Unfortunately, people are being forced to do that right now" all the same, Ms. DuPont-Kidd noted. Maryland, the District of Columbia and northern Virginia, along with parts of Ohio and Illinois, were the hardest hit by power losses, she said. PJM estimated that on Saturday, four million customers were in the dark. A customer could be anything from an apartment with a single resident to a multifamily building to a factory. By contrast, Hurricane Irene took out about three million in 2011. None of this means much if it's your house that lost power. But if you are in the dark, you may not be reading this anyway.