During the hot summer months, when electrical demand is at its highest, ISO — which coordinates the generators and operates the grid — constantly plans for the availability of roughly 32,000 megawatts of capacity. That quantity allows for a safety reserve since the actual peak demand is usually between 27,000 and 28,000 megawatts. During the fall, winter, and spring, demand is considerably less.
There are five nuclear plants on the system, and they consistently provide about 31 percent of our electricity. Nuclear plants cannot start or stop easily, so they run mostly constantly. Vermont Yankee may close next year.
There are 10 coal plants (some are dual fuel) on the grid. Since 2000, we have reduced our use of them. In that year, they provided 18 percent of our power; last year, they made just 3 percent of it. Brayton Point may soon close.
There are roughly 110 oil plants (varying sizes) in the grid. In 2000, they fueled 22 percent of our power; last year, they made just 1 percent of it. (There are also 45 dual-fuel oil plants.)
It is quite likely that coal and oil will continue to play a shrinking role in New England energy production. Our reliance on natural gas will continue to rise. There are about 45 gas plants on the grid, and they now fuel 52 percent of our power. That’s up from 15 percent in 2000.
Burning natural gas rather than coal and oil is an improvement. Gas emits half the carbon dioxide of coal, so it alters the chemistry of the atmosphere at a slower rate. But still, gas is a fossil fuel, and ultimately, its use must be severely curtailed.
The grid currently gets only 14 percent of its power from renewable energy: wind, solar, hydro, geothermal. And that percentage also includes energy from wood, biomass, landfills and refuse, so it’s less clean energy than is optimum.