Due to relatively low Natural Gas prices and improved thermal efficiency and economies of scale due to developments in turbine design, Natural Gas combined-cycle (NGCC) electric generating capacity in the United States has increased in recent years. Newer turbine technologies are more potent than older turbine technologies, resulting in lower operating costs.
As a result, in the United States, the average annual capacity factor, or utilization rate, for newer NGCC generators is marginally higher than for older, less powerful generators. The electric power industry in the United States added 5.8 gigawatts (GW) of combined-cycle generating capacity in 2020, taking the total NGCC capacity in the United States to 259.9 GW.
The utilization rate of the US NGCC fleet has gradually increased from an average of 35 percent in 2005 to more than 57 percent in 2020, as the US generation mix has moved away from coal and toward Natural Gas and renewables.
Between 2008 and 2020, 52 percent of the 51.1 GW of NGCC power in PJM came online. The capacity factor of these plants, which are the newest and hence more likely to use advanced turbine technology, was 71 percent in 2020, the highest of all regions and generator age groups. In 2020, the California Independent System Operator (CAISO) had the lowest average capacity factor for combined-cycle plants of all ages, at 41%.