The operational time of modern smart-phones with one filling of the accumulator is one of the most important performance parameter for the customers of new devices. This is the reason why extensive research has been performed in the fields of battery design and system optimization with regard on energy consumption. Due to the fact that the radio part of a smart-phone is one of the major energy consumers, a special focus has to be set on different approaches and strategies how to reduce the energy that has to be spent for the transmission of a certain amount of data. However, before new energy saving protocols can be efficiently developed one needs to have detailed knowledge on the different factors which impact the energy efficiency. In this paper, we present a measurement based energy model for IEEE 802.16e conform Mobile WiMAX devices. For this purpose, extensive measurements of the energy consumption of a Mobile WiMAX USB Stick have been performed for different system parameterizations, different data sizes and different application data rates. From the results of the measurements analytic models have been derived which allow for the calculation of the energy that has to be spent per successfully submitted bit. These analytic formulas can now be integrated in system level simulators for the evaluation of the energy efficiency of newly designed protocols.