<p>The Free Space Optical (FSO) is a wireless optical system that has many advantages such as low installation time, low installation cost, flexible deployment, high data rate, high data security, and unlicensed spectrum usage. However, FSO links degrade in the presence of bad weather conditions including rain, fog, and snow. In this paper, the Energy-Efficient Adaptive Power Transmission (EEAPT) system is proposed to adaptively adjust the required minimum transmission power based on the distance between the transmitter and receiver under real weather condition data in the Gaza Strip. The required transmission power is the minimum transmitted power at the transmitter that guarantees a predefined minimum value of the received Signal to Noise Ratio (SNR) at the receiver. If the required transmitted power exceeds the transmission capability of the transmitter, EEAPT performs decision making to classify the FSO link as an unviable link. In the case of an unavailable FSO channel, other communication systems such as Radio Frequency (RF) and optical fiber are employed for transmission. In addition, the effect of weather conditions in the Gaza Strip on the FSO channel is analyzed in this paper. Simulation results show that, compared with other fixed and adaptive transmission power schemes, the proposed EEAPT scheme improves the energy efficiency of the transmitter and the link availability of FSO links.</p>