In the United States, coal provided 56 percent of the electricity generated in 1992. Nuclear energy was the next largest contributor, supplying 22 percent. Natural gas provided 9 percent, while hydro-electric and renewables together supplied another 9 percent. Currently, the 109 nuclear power plants in the U.S. have an overall generating capacity of 99,000 MWe. To improve efficiency, safety, and performance, the lessons of 30 years of experience with nuclear powerplants are being incorporated into design criteria for the next generation of U.S. plants. The new Advanced Light Water Reactor plants will feature simpler designs, which will enable more cost-effective construction and maintenance. To enhance safety, design margins are being increased, and human factors are being considered and incorporated into the designs.