Energy demand overall the world increases rapidly in various sectors, one of the highest energy consumption sector is the building sector. Installation of PV systems is one of the solutions to cover this demand and will serve in promoting energy efficiency in the Palestinian municipalities in decreasing the electricity bill, and using the saved money in constructing new projects and improving the level of services provided to citizens. In this work, Al-Dahriya municipality has been taken as a case study. The municipality installed 20 KW of photovoltaic panels on the roof of the main building in 2015. The cumulative values for one year after installation the PV system represent a total consumed electricity by the main building was 71,506 kw, while the total generated power by the PV system that transferred to building was 32,664 kw, and 5323 kw exported to the grid with total generated power by PV system was 37,987 kw. The participation of energy that produced by the photovoltaic system is 53.12% of the total power demand of the building. The value of generated power varies between the summer months and winter months through the difference of the solar radiation intensity and the number of shinning hours, the largest reading of solar radiation intensity is in the summer months. The study ensures the importance of applying selected thermal insulation materials in order to decrease the heat transfer through the boundary wall of the building. Furthermore, this study covers the other buildings and utilities of municipality and recommended with certain issues in order to promote energy efficiency.