Regeneration and steam injection are both well proven as well as promising modifications which can boost power, increase thermal efficiency, part load performance and limit NOX emissions. However, their benefits are still largely unexploited. To investigate these modifications, a comprehensive but practical model is established as an essential improvement on the air standard models. Our multipronged modeling approach enables simultaneous monitoring and optimization of thermodynamic, economic and environmental performance. Additionally, it provides a more accurate analysis by using specifically calculated thermodynamic properties, precisely calculated adiabatic flame temperature, a realistic definition of regenerator effectiveness coefficient and updated cost parameters. Simulating this improved model, a detailed parametrical analysis of steam injected and regenerative gas turbine cycles is performed for varying pressure, steam injection and equivalence ratios. Optimal operating parameters are investigated considering the state of the art cycle parameters and component efficiencies along with non-equilibrium NOX and CO emissions. Contradictory traits of steam injection and regeneration as well as their combinations are presented and comparatively discussed. Conditions of maximum economic profit are demonstrated regarding the up-to-date equipment cost data and escalations in fuel prices. We suggest, this study will contribute to optimization of novel and future gas turbine designs and applications. (C) 2017 Elsevier Ltd. All rights reserved.