NarrowBand Internet of Things (NB-IoT) is an emerging cellular IoT technology that offers attractive features for deploying low-power wide area networks suitable for implementing massive machine type communications. NB-IoT features include e.g. extended coverage and deep penetration for massive connectivity, longer battery-life, appropriate throughput and desired latency at lower bandwidth. Regarding the device energy consumption, NB-IoT is mostly under-estimated for its control and signaling overheads, which calls for a better understanding of the energy consumption profiling of an NB-IoT radio transceiver. With this aim, this work presents a thorough investigation of the energy consumption profiling of Radio Resource Control (RRC) communication protocol between an NB-IoT radio transceiver and a cellular base-station. Using two different commercial off the shelf NB-IoT boards and two Mobile Network Operators (MNOs) NB-IoT test networks operational at Tallinn University of Technology, Estonia, we propose an empirical baseline energy consumption model. Based on comprehensive analyses of the profile traces from the widely used BG96 NB-IoT module operating in various states of RRC protocol, our results indicate that the proposed model accurately depicts the baseline energy consumption of an NB-IoT radio transceiver while operating at different coverage class levels. The evaluation errors for our proposed model vary between 0.33% and 15.38%.