The US electric system is highly reliable, and one basic reason for its reliability is that the opening of new power plants greatly outpaces the retirement of old ones. In fact, new plant openings are outpacing retirements by a 3:1 ratio.
Official data shows that 4,844 megawatts of new generation opened across America, while 1677 megawatts closed, during the first 4 months of 2012. www.eia.gov/electricity/monthly/.
Gas and wind dominate the new plant category, with gas leading. Approximately 2,770 megawatts of gas plants opened through April. Solar and biomass make up most of the remainder of new plant openings. The EIA data lists one new coal plant opening.
In the retirement category, coal plants account for a bit more than 1,000 megawatts of the retiring units, with gas plants second.
The steady opening of new gas plants and the retirement of old coal plants is a major factor moving natural gas toward being America's biggest source of electric generation.
Not surprisingly, the new capacity is much more fuel efficient and cleaner than the retiring capacity or the average capacity that is operating today.