ISO New England, which oversees more than 28,000 megawatts of generating capacity, forecast in its annual assessment that power demand this summer would peak at 24,200 MW given normal weather patterns, and 25,500 MW during an extended heat wave.

The current record is 24,967 MW, set on August 9, 2001.

One megawatt is enough energy to run about 1,000 homes.

But the ISO also warned that "several unexpected events could result in localized problems that could lead to tight power supply situations" for the 6.5 million electric customers living in Connecticut, Rhode Island, Massachusetts, Vermont, New Hampshire and Maine.

Electricity usage in New England peaks during the summer months on air conditioning demand, which accounts for about a third of all the power consumed on a hot afternoon.

"We still face several challenges: We need regular imports of power from Canada to ensure we have adequate supply, and we need to address transmission congestion that could cause capacity deficiencies," said Stephen Whitley, ISO New England senior vice president and chief operating officer.

Some of those challenges include: an extended heat wave; transmission bottlenecks in the populous southwest Connecticut and Boston areas; drought that could affect the generation of power; and lower power exports from Canada.

New England depends on Canada for about 10 percent of its electricity.

To hedge against these and other unexpected events, the ISO has put in place a plan to reduce energy use this summer, including financial incentives for large commercial users to curtail power consumption during periods of high demand.

TRANSMISSION BOTTLENECKS Most of the region's new power plants have been built outside the areas of highest demand -- southwest Connecticut and Boston -- and on hot days there are not enough high-voltage transmission lines to carry all the power needed to supply these populous areas.

Southwest Connecticut has one of the nation's most severe transmission reliability problems, the ISO said.

The ISO warned the situation in southwest Connecticut is so acute that "the loss of a major transmission facility or power plant could lead to the disruption of electricity supplies."

The constraints in Boston are similar to those in southwest Connecticut, but not as severe, the ISO noted.

Last summer, the failure of transmission lines near Stratford, Connecticut on a moderately hot day nearly resulted in blackouts that were averted only through an emergency dispatch of power from Long Island.

At the same time, several hundred megawatts of generation were "locked in" in Maine during a heat wave and unavailable for delivery to the rest of New England because there were not enough transmission lines to move the power out of Maine.

"Until improvements are made to the region's transmission system, ISO New England will have to carefully manage power system operations during peak demand periods this summer and for the next few years," the ISO's Whitley noted.