The reduction of load-dependent gear power loss is one of the key aspects in gear design. Therefore, a detailed power loss prediction and the local investigation of its drivers are essential. In this study, the model of Farrenkopf et al. is stepwise enhanced to match the real contact conditions as closely as possible. The impact of eliminating simplifications or assumptions is shown at each of the individual enhancement steps. The proper choice of the lubricant parameters, the coefficient of solid friction, and the gear system stiffness shows a great impact on load-dependent gear power losses and the local friction. It is explained how the load-dependent gear power loss of an individual tooth contact is derived from the transient local TEHL contact and subsequently the measurable load-dependent gear power loss. Considering a low-loss gear geometry, the simulation results are compared with experimental results and show a good level of conformity.