The Internet of Things (IoT) is the latest generation network that connects numerous devices via the internet. The element for increasing authorization in IoT applications, as well as the economic and industrial resource usage, is energy efficiency. This work focuses on optimizing joint power allocation, user selection, and number of activated devices (JPAUSAD) for many IoT devices, considering self-transmitted power and quality of service (QoS) with incomplete CSI. The procedure begins with the calculation of the initial configuration of power allocation (PA), user selection (US), and activated devices (ADs), followed by the optimization with the energy-efficient resource allocation (EERA). This results in the development of an efficient heuristic solution strategy for obtaining the best solution. Simulation results show that the effectiveness of the suggested algorithm with energy-efficient maximization is much better. The proposed JPAUSAD achieved better results with 98.34% of energy allocation (EA), 97.21% of power allocation (PA), 41.62% of end-to-end delay (EED), and 96.38% of throughput, when compared with the existing methods joint optimization of power allocation and user selection algorithm by applying Kuhn–Munkres algorithm (JPAUS-KM) and joint user scheduling and power allocation (JUSPA).