A routine using multiple methods is proposed for detecting and locating hot spots in power transformers based on thermographic measurements and advanced computational and analytical techniques. The proposed method identifies oxide and hydrocarbon gases dissolved in the insulation oil of power transformers and use the well-established key gas method to provide information about the cause of the hot spots, such as partial discharge, electric arc, and overload heating. The method then uses infrared mappings and temperature measurements to find the approximate location of the hot spots and, finally, the finite element method and an analytical formulation are employed to refine the location of the hotspots and the estimation of their temperature. The proposed method was developed during the design and manufacturing of a commercial 120 MVA generator step-up transformer, produced by a well-renowned manufacturer. The authors conclude that a method is a resourceful tool for identifying hot spots and could be used by manufacturers to identify and predict design and manufacturing failures.