By Scott DiSavino
July 17 (Reuters) - Power companies and regional grid operators in the U.S. Northeast said they have enough electricity to keep air conditioners humming on the fourth day of a brutal heat wave.
But despite the lingering heat, the region's utilities and power grid operators have not had to take any major steps to keep the lights on.
They have asked consumers to conserve power, deferred non-essential equipment maintenance and activated demand response programs to reduce energy usage in some areas, but there have been no widespread blackouts - just some scattered outages.
On Wednesday, New York State's grid operator again activated programs to reduce electric use for a third day in a row.
The New York Independent System Operator (NYISO), which operates the state's grid, said its demand response programs can reduce power usage by more than 1,250 megawatts. One megawatt can power up to 1,000 homes.
Demand response program participants are compensated for reducing electricity use - and could be penalized for not doing so - by raising air conditioner thermostats and by turning off unnecessary lights and other equipment, including elevators. Putting on-site generators into use also reduces the amount of power needed from the grid.
Temperatures in New York City, the nation's biggest metropolitan area, reached 94 degrees Fahrenheit (34 C) on Monday and Tuesday, and are expected to remain around 94-95 F through Friday before thunderstorms break the heat wave on Saturday, weather forecaster AccuWeather.com said.
ISO New England, which operates the six-state New England grid, forecast power supplies will be very tight on Thursday with a surplus of just 13 MW. Earlier Wednesday, the ISO forecast supplies Thursday would be at a slight deficit.
Some power traders said they were surprised next-day prices in New England for Thursday did not climb above the $130s per megawatt hour, the same as for Wednesday.
"It appears we will have the resources needed to meet peak demand, but conditions can change at any time and it always helps when consumers use electricity sensibly," ISO New England spokeswoman Marcia Bloomberg told Reuters.
Bloomberg said the ISO has not invoked any of its operating procedures to keep supply and demand in balance, but she said "If system conditions warrant, we are prepared to implement one or more of those procedures."
Those procedures, used by all grid operators, are designed to keep supply and demand in balance. They include demand response programs, power imports from neighboring regions, brown outs and, if all else fails, rotating blackouts, which became synonymous with the California energy crisis in 2000-2001.
ISO New England said it has never used rotating blackouts to reduce consumer usage. PJM, the biggest power grid in the United States, said it last used rotating blackouts in January 1994.
PJM said it did not expect to need to take any steps to reduce power usage on Wednesday.
PJM said peak usage was near 152,200 MW on Tuesday and forecast usage would reach about 156,000 MW on Wednesday and 158,600 Thursday before declining as the heat wave starts to break in the Western parts of its region.
That is still well below PJM's all-time record of over 163,800 MW set in 2011.
PJM operates the grid serving 61 million people in 13 Mid-Atlantic and Midwest states from New Jersey to Illinois and the District of Columbia.
In New York, NYISO forecast demand would peak at 33,400 MW Wednesday afternoon, which is close to the grid's all-time record of 33,939 MW set in 2006, before industrial and commercial companies reduced power usage during the recession.
On Tuesday, New York's peak reached 32,223 MW, which was below Monday's peak of 32,703 MW.
In New England, ISO New England said usage Tuesday peaked at 26,210 MW and forecast demand would reach 27,000 MW on Wednesday and 27,600 MW on Thursday, again still shy of the system's all-time peak of 28,130 MW set in 2006. Last summer, usage peaked at 25,880 MW in July.
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.
The biggest power companies in New England include units of National Grid, Northeast Utilities, Iberdrola, NextEra Energy Inc, Dominion Resources Inc, Entergy and Exelon Corp.