A computer simulation of combined and cogeneration gas turbine (GT) cycles with inlet air cooling was conducted. A life cycle cost analysis (LCCA) was carried out to compare the economic impacts of different cycle alternatives. The efficiency was around 50% for a simple gas turbine (203 MW ISO rating) with evaporative or fogging inlet air cooling. The calculated efficiency of the cogeneration cycle with inlet air cooling using absorption or vapour compression refrigeration was around 56%, while that for the combined cycle with inlet air cooling (absorption or vapour compression refrigeration) was around 60%. Under ISO conditions for the 203 MW GT, evaporative or fogging inlet air cooling at gas turbine intake is attractive because of simplicity and relatively modest hardware requirements. Initial cost of evaporative and fogging cooling was estimated $90800 and $79450 respectively. Higher pumping energy is required for fogging (17.5 MWh) compared with evaporative cooling (4.0 MWh).