CCGT combine the previous two technologies — steam turbines and combustion turbines — together to produce electricity. They use the direct combustion of air and fuel — primarily natural gas — to drive a combustion turbine, as well as to produce pressurized steam. Water is heated by the exhaust, or waste heat, from the first turbine, to create the steam to drive a second steam turbine.
By combining the two systems like this, the overall result is improved efficiency. That is, generators are able to produce more electricity from the same amount of fuel than would be the case with a single-cycle turbine. CCGT achieve thermal efficiencies of 52%-62%. The benefits associated with using CCGT for power generation include capitalizing on the currently low cost of natural gas, increased thermal efficiencies, and the ability to operate this type of generation as baseload generation.