Conventional evaluation approaches for complex technologies, such as gas turbine systems, typically use process simulators for modeling, which are usually complicated and time-consuming. In order to facilitate policy analysis, a simplified desktop model for gas turbine systems based upon the air-standard Brayton cycle is developed in Microsoft EXCEL. The simplified model incorporates key process details and includes a comprehensive cost model. The model is calibrated based on a typical "Frame 7F" heavy duty gas turbine fired with natural gas and syngas. The model generally produces accurate and reasonable estimates for performance and cost comparable to reference data. The model responds appropriately to different syngas compositions, such as based on variation in moisture content and CO2 removal. Changes in syngas composition lead to different syngas heating values and thus affect gas turbine performance and cost. The effects of changes in inputs on key outputs are evaluated. Six key inputs are identified that are critical in order to obtain accurate estimates. The simplified model provides detailed technical information in a format that supports strategic planning and analysis.