Public places like markets and others need to be permanently energized because of security issues and vital activities that take place. The demand is constantly varying over time of the day, rendering power supply unstable. For that reason, public places are lacking electricity at the time they need it more. Supplying demand energy using diesel fuel is so expensive and increases the amount of CO2 emitted. To help solve this problem, this work design an optimal stand-alone hybrid system composed of diesel machine, PV and Battery to permanently supply energy at a stable voltage and reduce greenhouse gas emission. The method consist of making the power balance of the equipment market, developing a mathematical model of each component of the hybrid system and solve for optimal size. The model developed was evaluated using data from Ouando market in Benin for which the demand of electric energy is 2817.171kWh/d. HOMER software is used for simulation and results were compared to the empirical data. The results demonstrate that to meet the power demand of the market, the power contribution of the sized PV plant is 907.2 kW. This reduces the fuel consumption of the diesel engine for 45% and decreases CO2 emission for about 55%