For the Internet of Things (IoT) applications that send a few bytes of sensor information infrequently, several long-range IoT technologies have been conceived. Narrowband IoT (NB-IoT) is one of them that stands out due to its extended coverage, high penetrability, and high reliability features. Among the primary goals set for the standard, low device power consumption is significant as the devices are typically deployed with batteries. In this paper, we characterize an NB-IoT device with respect to its energy consumption in different coverage classes for various scenarios. Based on the measurements, we estimate the lifetime of the device. We find that the lifetime of the device is significantly affected by the coverage class of the device. In order to augment the battery, we investigate the possibility of using ambient energy sources in the context of a smart home. For this we analyze real-world data sets, and find that the harvesting technologies can increase the average lifetime of the device. However, due to the spatio-temporal variations in the amount of energy that can be harvested, there are several challenges to be dealt with. We list the keys challenges of using energy-harvesting in NB-IoT, and those inherent to NB-IoT.