The number of large sensor systems is rapidly growing nowadays in many fields. Well-designed Big Data solutions are able to manage the enormous data flow and create real business benefits. One dynamically growing application area is precision farming. It requires robust and energy- efficient sensors, because the devices are placed outdoors, often in harsh conditions, and there is no power outlet “in the middle of a corn field”. Power efficiency is in general one of the major themes of the Internet of Things (IoT). According to the IoT vision, embedded sensors send their data to processing units (either located near to the sensor or on some intermediate ”gateway” device or in the cloud) using heterogeneous transport networks. Some sensors employ short-range network like Bluetooth and some ”gateway” device like a tablet. Other sensors directly connect to wide-area networks like cellular networks. This paper will analyze different communication patterns accomplished over GSM network from the viewpoint of the energy consumption of the sensor device with the assumption that the sensor is stationary. The measurements were done using two different GSM modems designed for embedded systems to ensure that the results represent a wider picture and not some implementation property of a particular GSM modem. Recommendations are given about the strategies applications should follow in order to minimize the energy consumption of their GSM subsystems.