By Scott DiSavino
NEW YORK (Reuters) - A heat wave blanketed the U.S. mid-Atlantic and Northeast on Thursday, sparking brownouts in New York City and forcing utilities across the region to ask customers to conserve electricity.
Despite local transmission problems, regional power grid operators in New York, New England and the 13 states served by the PJM regional transmission group expected to have enough power to meet soaring demand on the second day of the hot weather.
Thursday's high of 94 degrees F (34 C) in New York, the nation's biggest metropolitan area, matched the high Wednesday, which was the first day of summer. Friday's high is forecast to ease to 92 degrees, to be followed by weekend highs in the mid-80s, only a few degrees above typical late June temperatures.
The National Weather Service extended a heat advisory until Friday evening for New York City.
New York utility Consolidated Edison Inc continued to reduce power voltage, known as a brownout, in neighborhoods in the boroughs of Queens and Brooklyn on Thursday due to equipment problems.
Only 100 customers were without power by Thursday afternoon, down from about 600 earlier in the day, Con Edison spokesman Chris Olert told Reuters.
On Wednesday night, Con Edison reduced power and asked customers to curtail use of non-essential appliances in affected neighborhoods to protect equipment and maintain service as crews work to solve the problem.
In brownouts, incandescent lights are dimmer, water is warm rather than hot, and motors move slower.
The New York Power Authority (NYPA) and New York's power grid operator, the New York Independent System Operator (NYISO), activated programs in the city and parts of the state on Wednesday and Thursday to curb peak demand.
Under the programs, which compensate consumers for reducing usage, subway cars could lose air conditioning, people may wait longer for elevators, and lights in office lobbies may be dimmed.
Still, utilities say the reductions go a long way to helping keep the lights on and air conditioners humming for everyone, as well as keeping power prices from climbing too high.
Besides reducing usage, participants in the demand-response programs can run onsite power generators to take the load off the grid.
The PJM regional transmission grid issued a hot-weather alert for Wednesday and Thursday, telling generators and transmission owners to delay maintenance on plants and power lines until the heat wave passes.
PJM is the biggest power grid in the United States, serving 60 million people in 13 mid-Atlantic and Midwest states.
Power prices in PJM, the most active hub in the United States, jumped about 70 percent to the $150s per megawatt hour for Thursday delivery. New England prices jumped almost 80 percent to the $170s for Thursday.
New England's grid operator also asked generators and transmission owners to put off maintenance during the heat wave.
The NYISO forecast demand on Thursday would reach 33,500 megawatts (MW), approaching a state record of 33,939 MW set in August 2006.
PJM expects demand for power to peak at 151,767 MW on Thursday, well below an all-time high of 163,760 MW set last July.
ISO New England, which operates the grid in the six New England states, forecast peak demand would hit 26,620 MW on Thursday, below the region's all-time high of 28,130 MW set in August 2006.
The biggest utilities and generators in the Northeast include units of Illinois-based Exelon Corp, Ohio-based FirstEnergy Corp and American Electric Power Co Inc, North Carolina-based Duke Energy Corp and Con Edison.
(Reporting By Scott DiSavino in New York and Eileen O'Grady in Houston; Editing by Jeffrey Benkoe and Peter Cooney)