This thesis deals with the study of existing energy utilization and the integration of solar photovoltaics into an existing diesel grid-connected hybrid system to improve the reliability of continuous power supply and to control energy dissipation in an Et hio telecom base transceiver station. The main goals of implementing a grid -connected PVdiesel hybrid system are to reduce diesel consumption, reduce carbon emissions, reduce network interruption, and maximize profit from energy saving. The load profiles of the base transceiver station and office facility are necessary for designing the system. They have used electricity supplied from one source and have pre-designed the size of the PV generator, the capacity of a storage system, the rating of the diesel generator, and the inverter type/size selection. The load profile data is based on the average daily energy consumption of both BTS (DC load) and the office (AC load). Detailed simulations and financial analysis are performed with HOMER to compare different systems and their viability. The simulation includes the existing system, a grid-connected diesel generator system, and adding a solar PV system to the existing one. After the hybrid system is determined, a detailed design is done to optimize the lowest -cost grid-connected PVdiesel hybrid system. The final simulated grid-connected PV-diesel hybrid system is suggested with a PV capacity of 27kW, an existing diesel capacity of 40 kVA, an inverter output of 17.7kW, and two battery bank nominal capacities of 1000Ah. The system's renewable fraction is 69.3%. The grid-connected PV-diesel hybrid system is selected to produce electricity for $0.42/kWh.This cost is significantly lower than the $1.27/kWh paid to the existing energy supply. The estimated fuel cost was reduced from $7329/year to $922/year, 87.4%, and CO2 emission was reduced by 78.4% annually. In addition, providing a linear control mechanism of fiber signal and energy supply systems by using coding on Arduino with circuit design and simulation by Prot eus results in reduced energy dissipation during no network services. Keywords: Base Transceiver Station/BTS, energy optimization and control, uninterrupted power supply, telecom power quality