Natural gas fired combined cycles have enjoyed increasing success in power generation over the past several years, driven to a significant degree by their high efficiency. This paper discusses development of a fuel moisturization system targeted at new construction that improves plant efficiency (∼0.16% points.), increases plant output (∼1.3%), and reduces NOx emissions (10%–15%). Since the inception of combined cycles, improvements in efficiency and power density have been largely driven by ever higher gas turbine operating temperatures. The steam bottoming cycle has also been refined, first by the addition of multiple pressure levels, then reheat, and more recently fuel heating, to utilize the gas turbine exhaust energy ever more efficiently. Further improvement is most effectively realized by a structural refinement of the cycle that allows more of the low level waste heat to be recovered to the fuel, where each additional Btu or Kcal is one fewer that needs to be purchased as fuel. This goal has been achieved with development of a Fuel Moisturization System to moisturize and superheat the fuel gas entering the gas turbine combustion system.