Determining an optimal energy mix is essential for policymakers in many countries to enhance energy efficiency, promote economic development in the energy sector, mitigate greenhouse gas emissions, and elevate the renewable energy sources' utilization. This issue has gained more significance recently due to pressing concerns about climate change and the escalating global demand for energy resources. Prior research has explored facets of energy mix optimization to varying extents. However, none of them have well addressed the simultaneous consideration of both environmental and economic effects of energy resources in developing optimal energy mix models. This study proposes an optimization-based methodology for determining the optimal energy mix in electricity generation from various energy sources in the United Arab Emirates while simultaneously minimizing economic and environmental costs. The optimization model helps to minimize the total cost for future investments in electricity generation capacities over 30 years, which includes the installation cost of new power plants, the fixed cost for annual operation and maintenance, the variable cost for operation, and the environmental cost associated with CO2 emissions from different energy sources. The model addresses energy demand requirements, annual installation capacities, peak demand, and renewable energy technologies. The results of this study show that a substantial portion of the future electricity capacity installation is acquired from solar photovoltaic energy, followed by natural gas. In addition, CO2 emissions rate of electricity generation in 2050 can be reduced by around 10% with the proposed optimization model. While it can be reduced by 20% when limiting fossil fuels, by 17% when increasing the maximum capacity installation of solar PV, and by 40% when considering only CO2 emissions.