In various applications, thermoelectric active cooling systems can help maintain electronic devices at a desired temperature condition better than passive coolers. Thermoelectric Coolers (TEC) are especially useful when the temperature of a device needs to be precisely controlled. This study proposes a user-friendly graphical method for calculating the steady-state operational point of a TEC based active cooling system, including the heatsink role. The method is simple and intuitive and provides comprehensive information about the cooling system such as its feasibility, required heatsink, the TEC current, temperatures of the cold side and others. The method could help designers to examine and choose a thermoelectric module from catalogues to meet a specific cooling problem. To start using the method, designers need only the experimental TEC data provided by practically all manufacturers of such devices. The experimental results of this study verify the high accuracy of the proposed model and graphical approach.