Natural gas-fired generators accounted for 43% of operating electricity generating capacity in the United States in 2019, according to the U.S. Energy Information Administration (EIA). The generators provided 39% of electricity generation in 2019, and this is more than any other source.
Most of the natural gas-fired capacity added in recent decades use combined-cycle technology, which surpassed coal-fired generators in 2018 to become the technology with the most electricity generating capacity in the United States.
Technology improvements have led to improved efficiency of natural gas generators since the mid-1980s when combined-cycle plants began replacing older, less efficient steam turbines. With steam turbines, boilers combust fuel to generate steam that drives a turbine to generate electricity. Combustion turbines use a fuel-air mixture to spin a gas turbine. Combined-cycle units are a combination of the previous technologies: A fuel-air mixture spins gas turbines to generate electricity. And the excess heat from the gas turbine is used to generate steam for a steam turbine that generates additional electricity.
Combined-cycle generators typically operate for extended periods, while combustion turbines and steam turbines are usually only used at times of peak load. Few steam turbines have been installed since the late 1970s, and many steam turbines have been retired in recent years.
Combined-cycle systems are more efficient than steam or combustion turbines alone, and the newer combined-cycle systems are more efficient than those installed a decade ago. Changes in efficiency have reduced the amount of natural gas needed to produce the same amount of electricity, according to the EIA. Combined-cycle generators consume 80% of the natural gas used to generate electric power but provide 85% of total natural gas-fired electricity.
Every U.S. state, except Vermont and Hawaii, has at least one utility-scale natural gas electric power plant. Texas, Florida and California, the states with the most electricity consumption in 2019, each have more than 35 gigawatts of natural gas-fired capacity. In many states, combined-cycle systems comprise the majority of the capacity. However, steam turbines account for 44% of natural gas capacity in New York, and combustion turbines provide 67% of the capacity in Illinois.