According to federal law, electricity prices are determined at least in part by the lowest-priced power source in the pool, which in this case is almost always Indian Point. That's because once investors recoup the high cost of building a nuclear plant, the electricity it generates typically costs far less than most other forms of electrical generation.

During planned outages, the Department of Energy requires that electrical sources used to substitute for Indian Point provide power at the same cost ratepayers are normally charged.

60% More Energy Use in Summer

It's a different story with unplanned outages, such as summer blackouts, during which consumers don't get price protection. This is one reason why electricity bills rise during periods of high use and occasional power plant outages. 

During peak summer periods when air conditioners run constantly, New York City uses approximately 13,000 megawatts of electricity, according to NYISO data. This represents an up to 60 percent increase above the average level of energy use.

Over the past three years, Indian Point has experienced seven unplanned shutdowns. They were attributed to a series of unexplained mechanical failures, including rising water levels in its massive stream generators; a large hot water leak; and activation of a fire-suppression system. 

Meanwhile, New York City, hobbled by old and overused transmission lines, has limited access to the abundant amount of electricity that is produced upstate and in Canada, including relatively cheap hydroelectric power generated in Buffalo. This makes Indian Point's contribution hard to replace during periods of peak demand.

Westchester County, where Indian Point is located, faces a similar if not more severe situation. The county's nearly one million residents get up to 25 percent of their electricity from Indian Point. But Westchester, unlike New York City, has few internal power-generating alternatives.

"The capability of the existing electric transmission system is simply not sufficient to allow available upstate New York resources to meet Southeast New York needs if certain generating resources, such as the Indian Point units, become unavailable," Rick Gonzales, senior vice president of NYISO, told SolveClimate News.

What About Energy Efficiency?

Experts agree that energy efficiency and conservation measures could make up for some of the electricity lost if Indian Point suddenly closed. But even Audin, a staunch opponent of the plant, said that efficiency and conservation alone "cannot replace Indian Point's output."

Merely installing insulation upgrades, energy-saving florescent light bulbs and similar steps would not be enough to make a significant dent in electricity usage, agreed Van Nostrand of the Pace Climate and Energy Center.

Still, he estimates that energy audits combined with deep home and building retrofits, ductwork and more efficient heating, ventilating and air-conditioning, or HVAC, units could potentially reduce electricity demand by up to 1,000 megawatts, approximately half of the electricity that Indian Point generates.

But this would take money, new regulations and most importantly time, he said, which doesn't jive with the wishes of many Indian Point opponents, who are calling for an immediate shutdown.

Thousands of Megawatts Short

The 40-year licenses for its two active reactors, units 2 and 3, are scheduled to expire in 2013 and 2015, respectively. To continue operating, they must be renewed.

Residents and politicians frightened anew by Japan's Fukushima disaster are pushing for the reactors' closings. In response, the state Senate Standing Committee on Energy and Telecommunications was one of many oversight institutions to call hearings recently to determine the safety and value of Indian Point.

Its specific concern when it met in May was how New York City and Westchester County would fare if Indian Point units are unavailable as a result of a natural disaster in the summer of 2011. Gonzales, NYISO's senior vice president, testified on May 12 before the committee.

In his testimony, he considered state energy efficiency programs. He took into account declining electrical needs caused by the recession. And he included over 1,000 megawatts of new power plants expected to go online in the New York City area, including 500 megawatts from the natural gas-fired Bayonne Energy Center and 576 megawatts from Astoria Energy II, another gas plant.

With all this considered, he told the State Senate: If a natural disaster destroys Indian Point's ability to generate its standard 2,000-plus megawatts of electricity this summer, New York City and counties in the lower Hudson Valley could fall between 1,385 and 2,042 megawatts short at peak times, depending on how hot the summer proves to be.

This raised the question of whether local-area replacement resources could be available in the short term — as early as this summer — if Indian Point were to close. 

"Between now and 2013," Gonzales responded, "there are very limited options."

Without Indian Point's power this summer, New York City, still recovering from the financial crisis that began on Wall Street, could face rolling blackouts.