In recent years, The Internet of Things (IoT) is the most popular technology that is used in many applications. So, when the IoT system is implemented, it is important to reduce the power consumption and increase the lifetime of nodes in the system. Energy efficiency becomes a vital parameter. Many factors affect energy efficiency such as distance between the transmitter (sensor node) and receiver (sink node) and the number of bits will be sent. Data aggregation plays an urgent role in power saving. In this paper, an IoT system for a stadium is implemented to monitor the health condition of football players and compare between three scenarios one of them without using data aggregation and the second with using repeaters and the third with using data aggregation to approve that applying data aggregation in an IoT system will enhance network lifetime and decrease power consumption due to reducing the packets transmitted by percent depend on the number of aggregators and the number of sensor nodes. For the study cases with using four fixed cluster heads. In the case of two player, the bytes reduction through the network by percent of 24%. This percent increase to reach 50% in the case of five players.